Current topics in Biogeography

Exploiters, Adapters and Avoiders; The Impact of Urbanization

2012-02-14T09:37:00.000-08:00

By Sarah Rose

Most people know the Aesop’s tale of the Town Mouse and the Country Mouse in which the town mouse is stunned that the country mouse lives on bland food and in dull surroundings. When the country mouse visits the city he is terrified of the dog and decides that country life is for him. The story has been told around the world in many forms, each with a slightly different twist, but each one casting a little insight into the challenges we have created for all wildlife. Yet now, instead of having to travel many miles to the city we are building cities where the country used to be.

Humans love their big cities; skyscrapers reaching to the sky, smooth paved roads for easy travel, homes with room enough to house all our precious trinkets, and stores located conveniently on every corner. We take what used to be forests, fields and wetlands and create shopping malls and suburban developments where we can each grasp a little of the American Dream. For a few animals this is a dream come true, a chance at the lifestyle they feel they could, and do, become accustomed to. There is plentiful food, and shelter from the cold. Some species are so adapted to their human companions they can thrive in this cozy relationship. Wherever humans are found so are they, and usually in great numbers. Yet for many others the story is one of eviction from their homes, extreme competitive pressures and for some extinction.

In general there is a loss of biodiversity with an increase in urbanization. This is true across multiple groups of organisms; plants, mammals, birds, insects, and fish. Urban areas increase the opportunity for non-native species to be introduced, adding competition to the other factors that impact the native species. Urbanization, in many cases, destroys the native habitat. Although some remnant fragments may exist, the overall area is permanently altered. This change can benefit some species, but the majority is negatively impacted by it.

One way of looking at species response to urbanization is to place organisms into one of three categories: urban exploiters, urban adapters and urban avoiders.

House sparrow. © Sarah J. Rose

Urban exploiters are those species that have a close relationship with humans. In many cases we consider them pests, and in North America many are non-native invasive species. Urban exploiters are almost completely dependent on human subsidies. These would include animals like cockroaches, Norway rats, house mice, house sparrows, European starlings, and rock pigeons, just to name a few. They tend to be omnivores (eating a mixed diet of plants and animals) or granivores (feeding predominantly on grains and seeds). They tend to be non-migratory, gregarious, and able to breed in or around buildings.

Raccoon © Sarah J. Rose

Urban adapters are species that in wild habitat would be considered “edge” or early successional species. These are species that take advantage of areas where two habitat types meet or where disruption has altered the habitat. They rely on natural resources, but are able to utilize human subsidies. Raccoons, coyotes, groundhogs, opossums, jays, robins, crows, cardinals and many ornamental shrubs are considered urban adapters. They are very common in suburban habitats, can tolerate urban conditions, but also survive in rural areas.

Prairie Chicken © Sarah J. Rose

Urban avoiders are those that are very sensitive to the changes in habitat that occur with urbanization. They are the first species to disappear in urban settings. This would include large mammalian predators such as grizzlies and cougars, large mammalian grazers such as bison and elk, forest dwelling insectivore (insect eating) birds such as the Acadian flycatcher and wood-peewee, ground nesting birds such as prairie chickens and northern bobwhite, and late successional and old growth plants.

This categorization is helpful as it can identify which organisms are at the greatest risk, and therefore which should be most closely monitored. With that said one should note that each species has its own unique response to urbanization, and therefore this response could be looked at as more of a continuum than as strict categories. Some species are more adaptive, and some are greater avoiders. By using these insights we can focus our attention on where it is needed the most.

With the constantly growing human population the urban sprawl continues to consume native landscapes. It is the urban avoiders that pay the price. Conservation efforts are helping by setting aside native areas and restoring landscapes. Research is continuing to develop insights into ways that we can live in better harmony with those organisms that avoid us when they can. Education is one of the key factors, suburban residents are more conservation focused than their rural counterparts, thus we need to develop outreach programs and educate adults and our children. We need to appreciate the wildlife, discover what they need to survive, and make sure that when constructing our homes we are giving nature the ability to choose the country lifestyle if that is what it wants.

References
Kark S, Iwaniuk A, Schalimtzek A, Banker E (2007) Living in the city: can anyone become an 'urban exploiter'? Journal of Biogeography, 34, 638-651.

McKinney ML (2002) Urbanization, biodiversity, and conservation. Bioscience, 52, 883-890.

Shochat E, Lerman SB, Anderies JM, Warren PS, Faeth SH, Nilon CH (2010) Invasion, competition, and biodiversity loss in urban ecosystems. BioScience, 60, 199-208.

Invasive species, climate change and evolutionary progress

2012-02-13T12:27:00.000-08:00

Contributed by David Poole

Cheatgrass (Bromus tectorum) in the Intermountain west
is a well-known invasive species that has taken over the
native grasslands of the region.

In exploring the relationship between invasivity and evolution, it occurred to me that the spread of invasive species along with climate change are probably the two biggest factors influencing evolution today. The dispersal of species worldwide has been enabled in the past few hundred years as a result of global exploration. Emissions of carbon dioxide have increased significantly since the Industrial Revolution, accompanied by a rise in global temperatures. An article by Mooney and Cleland (2001) addresses both of these factors better than most. They recognize the effects of climate change on the changing biota, and describe the interactions between the invaders and the invaded leading to evolutionary progress. These two human induced factors are perhaps the most important drivers of evolution in our time.

The authors explain we are “witnessing the consequences of a number of truly grand, but unplanned, biological experiments. They are the result of the activities of a massive human population…” (Mooney and Cleland, 2001). As an experiment, however, there is no separate experimental “control” and knowledge must be gleaned from the historical record. In describing the nature of the problem, Mooney and Cleland (2001) point out it has been suggested by some that our apparent global condition is nothing new, but “the rate of change in the composition of the atmosphere” and the biota due to “migration of species among continents” is faster than at any other time in history. Man has a wide range of temperature in which he can function, and has also exhibited time and time again the ingenuity necessary to solve problems pertaining to maintaining thermal equilibrium. Unfortunately, plants and animals do not adapt as quickly or easily, and extinction is not reversible. I want to review in more detail some of the observations made by Mooney and Cleland, and others, in regard to climate change, invasive species and evolutionary progress.

Mooney and Cleland (2001) quote the well-known University of California, Davis professor of marine ecology and paleoecology Geerat Vermeij as saying “… if newcomers arrive from far away as the result of large-scale alterations in geography or climate, the change in selective regime and the evolutionary responses to this change could be dramatic.” The authors go on to describe changes in the evolutionary landscape and biota past and present, highlighting many examples to help explain the concepts and consequences. They provide statistics on the rate of invasion of alien species into San Francisco Bay and fish species introductions into the United States. It is pointed out that introduced species “may stay at a fairly low population size for years and then explode at some later date–the so-called lag effect.” This may be due to the normal population growth lag phase, but it can also be due to biotic or abiotic environmental changes or even due to changes in genetics of the founder populations (Crooks and Soule, 1999). They call it “lag debt” (Mooney and Cleland, 2001).

House sparrow (Male)

The article outlines both direct and indirect consequences of mixing native and invasive species. Among the direct consequences are evolutionary adjustments of the invader and the invaded. Invading species often have larger body size or plant size. This is believed to be due to the lack of competition for resources in the new environ and also where they are not subject to natural predation (Blossey and Notzwold, 1995). The example of an English sparrow introduced in North America in 1852 was used to illustrate. The bird species developed larger body size, modified feather coloration and established a large geographical range (Johnston and Selander, 1960). Native species often respond quickly to introduced species. An example was five species of moths from the genus Hedylepta that had developed over the past 1000 years became threatened by wasps and flies introduced as agricultural pest control (Zimmerman, 1960).

Hybridization and introgression, the backcrossing of two plant populations to introduce new genes into a wild population, were discussed in some detail with many examples provided. The origination of new taxonomic species from hybridization is possible using these techniques. Allopolyploids (individuals or cells with two or more sets of chromosomes derived from two different ancestral species) can originate from hybridization of native and invasive species. Examples are the salsify (Tragopogon) in North America and ragwort (Senecio) in Great Britain.

Brown trout (Salmo trutta) introduced to New Zealand

Indirect or secondary evolutionary consequences of introducing exotic with native species are that they can result in changes to behaviors and traits of the invaded as well as other species with which they have a functional relationship. An example of brown trout introduced into the streams of New Zealand starting in the mid-1800s was used to illustrate. Not only did the brown trout drive local populations of native fish to extinction, this, in turn, changed the behavior of the native mayfly nymphs and also the behavior of crayfish (Townsend, 1996). Behavioral shifts can occur both as a response to the new invader or in response to the new biotic community that the invader encounters. Other indirect consequences, including niche displacement, competitive exclusion, mutualism, and, again, extinction were discussed and many examples provided for each. Introducing new species into an environment is risky and problematic, particularly when the introduced organism causes damage to other species. For this reason, active species management requires great care and forethought.

The authors made the following tentative conclusions:

“Invasive predators…[that cause extinction] represent an irreversible removal of evolutionary potential.”
“…few examples of extinction have been associated with competitive interactions…This indicates either that extinction by competition is a slower process than extinction by predation…or that communities are not as ‘full’ as most ecological theories presume”
“Persistent and unexpected consequences [can occur].”

Quoting further from the concluding remarks section the authors sum up our condition:

“…ecosystems of the world have been altered by the activities of humankind…that are effecting the atmosphere and the climate…The mixing of formerly separated biota, and the extinctions these introductions may cause, are essentially irreversible…We are now developing a whole new cosmopolitan assemblage of organisms…with large consequences not only for the functioning of ecosystems but also for the future evolutionary trajectory of life.”

References:

Blossey B, Notzwold R (1995) Journal of Ecology, 83, 887–889.

Crooks JA, Soule ME (1999) In O Sandlund, PJ Schei, A Viken (Eds.), Invasive Species and Biodiversity Management (103–125), Dordrecht.

Johnston RF, Selander RK (1960) Evolution, 14, 548–550.

Mooney HA, Cleland EE (2001) The evolutionary impact of invasive species. National Academy of Sciences colloquium, "The Future of Evolution", 98, 5446–5451. Irvine

Townsend CR (1996) Biological Conservation, 78, 13–22.

Zimmerman EC (1960) Evolution, 14, 137–138

Images courtesy of Flickr and Wikimedia Commons (licensed for creative commons usage.):

1. Lavin M http://www.flickr.com/photos/plant_diversity/6127008871

2. Flickr user tgreyfox - http://commons.wikimedia.org/wiki/File:Passer_domesticus_-British_Columbia_,_Canada_-male-8a.jpg

3. Le Zouave Zouavman
http://commons.wikimedia.org/wiki/File:Brown_trout.JPG

Global Climate Change: Affecting Disease Rates?

2012-02-06T12:58:00.000-08:00

by Kelsey R. Fultz

In the past few decades, scientists have studied the impacts of global climate change on human and non-human animal populations. Temperature extremes, flooding, drought, hurricanes and other natural disasters have had and will continue to have detrimental effects on populations, resulting in shifts in geographical range and life history traits, reduced health and increased mortality (Easterling et al. 2000). Combined, these effects have the potential to create a perfect storm for diseases humans contract from other animal species, such as malaria and Lyme disease.

The mosquito Anopheles gambiae, vector of the parasite Plasmodium, which causes the human disease malaria. (Image from Wikimedia commons.)

These types of diseases are known as zoonotic and/or vector-borne diseases. Zoonotic diseases are those that cause disease in animal species but can also be transmitted to humans. They can be transmitted either via a vector, such as the black-legged tick which transmits Lyme disease, or through direct infection. Vector-borne diseases need not be zoonotic, however. These diseases are particularly sensitive to the impacts of global climate change, because climate change can influence the distribution and abundance of not only their hosts but also their vectors. A recent study by Mills, Gage, and Khan described a number of mechanisms by which climate change could affect zoonotic and vector-borne disease frequency in humans, reviewing the evidence for each (2010).

First, by affecting distribution host, vectors, and the pathogen itself, global climate change has the potential to increase infection rates. Poleward range shifts have been documented in a number of species in response to increasing temperatures. The castor bean tick (Ixodes ricinus), which is the vector of Lyme disease and tick-borne encephalitis, has experienced such a range shift, and this shift is associated with a higher incidence of tick-borne encephalitis in the region (Mills et al. 2010). Changes in climate and geographic range can in turn affect the abundance of hosts and vectors, which has a direct impact on infection rates. The more individuals in a population, the more likely the disease can spread – and disease carries can come into contact with humans.

Malaria risk across the globe. Poleward range shift in the mosquito vectors of malaria could introduce malaria to new parts of the world. (Image from Wikimedia Commons.)

While a greater incidence of disease carriers can increase infection rates in humans, another factor can affect infection rate – the pathogen load. A host or vector is less likely to infect a human when the pathogen is only present at low levels in their system. Changes in climate have the potential to affect pathogen loads, such as in the case of malaria. The Plasmodium parasite that causes malaria in humans can only develop within the mosquito at a certain range of temperatures (Patz and Olson 2006). Increased temperatures due to global climate change could increase the proportion of parasites that develop, and therefore the probability of infection (Mills et al. 2010). Other climate variables could also have an effect, depending on the particular pathogen and its hosts/vectors, including precipitation and humidity.

The same changes in climate that can affect the distribution, abundance, and pathogen load of host and vector species can also affect the distribution of humans. In many areas of the world where humans grow their own food locally, their livelihood depends on the climate. Flood, drought, and other weather extremes predicted from global climate change could very well force them to move. In one instance, the increased movement of humans toward water sources following drought was associated with increased infection rates of the disease leishmaniasis. Leishmaniasis is vectored by the sand fly, which happened to be found in high concentrations around the water sources (Thompson et al. 2002).

While it is apparent that the effects of global climate change appear to be exactly those that would impact the spread of zoonotic and vector-borne diseases amongst humans, in practice the patterns we observe are complicated by multiple factors. In order to map the changes in infection rates, baseline infection rates must be available, along with detailed information regarding local changes in climate. Studies that help to identify, track, and document outbreaks are imperative (Mills et al. 2010). The more we discover regarding the link between global climate change and disease, the better able we will be to combat the threat in the future.

References cited:

Easterling DR, Meehl GA, Parmesan C, Changnon SA, Karl TR, Mearns LO. (2000) Climate extremes: Observations, modeling, and impacts. Science, 289, 2068-2074.

Mills JN, Gage KL, Khan AS (2010) Potential influence of climate change on vector-borne and zoonotic diseases: a review and proposed research plan. Environmental Health Perspectives, 118, 1507-1514.

Patz JA, Olson SH (2006) Climate change and health: global to local influences on disease risk. Annals of Tropical Medicine & Parasitology, 100, 535-549.

Thompson RA, Wellington de Oliveira Lima J, Maguire JH, Braud DH, Scholl DT (2002) Climatic and demographic determinants of American visceral leishmaniasis in northeastern Brazil using remote sensing technology for environmental categorization of rain and region influences on leishmaniasis. The American Journal of Tropical Medicine and Hygiene, 67, 648-655.

Warfare and Biodiversity: A Delicate Frontline

2010-03-10T09:51:00.000-08:00

Contributed by Michael Durst

Biodiversity hotspots have been on the frontline of conservation efforts for about the past twenty years. Initially defined as an area supporting at least 1500 species of endemic vascular plants and having lost at least 70% of its vegetative cover, hotspots have also come to be considered in terms of total numbers of endemic threatened or endangered species, both plants and animals, relative to the amount of original cover no longer remaining. These hotspots have become largely accepted as highly prioritized for conservation and protection by international agencies and governing bodies. However, it is also the case that the majority of the planet’s hotspots occur in politically unstable regions and are often subject to the consequences of violent conflicts.

Between the years of 1950 and 2000, more than 90% of armed conflicts took place in countries housing biodiversity hotspots, and even more alarming is that more than 80% of these conflicts were directly in the hotspot zones. Many of these regions were affected multiple times by various conflicts throughout the years, with some conflicts being present almost continuously during these times.

Some potential reasons for such conflict concentration in the hotspot regions, as well as the problems facing biodiversity, are not difficult to imagine. The often remote landscapes of such regions are strategically attractive to many rebel and insurgent groups, providing good refuge and a base at which to build operations. At least equally important to consider is the resource richness of hotspot areas, and how this too could attract not only such groups as mentioned, but also local governments seeking additional resources for soldiers, civilians, and potentially as a means to bolster funds (such as precious gemstone mining and valuable timber logging).

Resource and land exploitation may be the two most apparent consequences of conflicts in hotspots, but these are just a ripple on the lake of associated problems. Other issues directly related to militant inhabitance are present as well; local species are often hunted in great numbers, for food, sport and profit, and land it is not uncommon for land to be cleared for the cultivation of illegal drugs. Aside from such direct physical effects, conservation programs present in those areas must often be abandoned, and funding for conservation are in many instances reduced or cut for increased military costs, which unfortunately also proves relevant during post-war when debts are to be repaid and monetary support is needed for oft-unstable governing bodies. A major consequence of serious conflicts is also the displacement of native human populations, whose primary concerns are for establishing shelter and feeding themselves and their families, and not necessarily the conservation of local biodiversity.

Amidst such turmoil, there can be glimmers of hope for future conservation. “Buffer zones” between opposing forces can prove to be biodiversity refuges, and former military land can serve as great acquirements for protection of present biodiversity; in times of post-war there can also be short periods of lessened stress on resources and reluctance of humans to expand into areas of uncertain safety. In any such instance cases must be treated individually, but treatment must also be planned and swift to make such opportunities advantageous for continued conservation in regions where such important biodiversity has suffered in the wake of violent conflict.

REFERENCES

1. Hanson, T., Brooks, TM., da Fonseca, GAB, et al. (2009). Warfare in biodiversity hotspots. Conservation biology, 23(3), 578-587.

2. Myers, N., Mittermeier, RA., Mittermeier, CG, da Fonseca, GAB, Kent, J. (2000). Biodiversity hotspots for conservation priorities. Nature, 403, 853-858.

The Argentine Ant Menace: Crushing Other Ant Species

2010-03-10T09:41:00.000-08:00

Contributed by Stephen Berecki

The Argentine ant is an invasive species that has spread from its native home in South America to most of the globe. They are now found on all continents (other than Antarctica), and are displacing the native ant species with which they come into contact. As a result, they are disrupting other organisms as well. For example, some lizards depend on specific ants for food and if those ants are gone, the lizards are in trouble. These ants have spread mostly thanks to humans. Crossing over large areas by hitching a ride with humans (or any other way it can hitch a ride) is called long-distance-jump-dispersal. This is the only way these critters can cross oceans and impenetrable landscapes. The Argentine ants are unique in the fact that the queens do not fly to new areas to make new colonies. This means they rely on walking to a new area if they want to colonize it. If there is a body of water, mountains, or just a large patch of unfavorable land, it is basically impossible for these small animals to make the journey on their own. This is why the Argentine ant mostly relies on humans to spread to other areas.

Argentine Ants (image from Wikimedia Commons)

There are a few reasons why the Argentine ant is so successful in competition with other ant species. The simplest is the fact that in lands far away from home, they escape from predators and parasites. One example is the phorid fly that parasitizes only the Argentine ant. Phorid flies lay eggs inside the ant and the larvae eat the ant, resulting in a nasty death. Another reason the Argentine ant is so successful is that all of the different Argentine ant colonies are not hostile towards each other, which is called unicoloniality. Most ants will only be friendly towards members of the same colony, even if it means competing with other colonies of the same species. This gives the Argentine ants a distinct advantage because they are not all competing with each other. Instead of a bunch of small ant colonies competing with each other, it’s a bunch of small ant colonies competing against a huge united Argentine ant colony. The final main reason for success is these ants are clever by harvesting sugars (i.e., honeydew) from other insects, like aphids. The ants will protect these insects and, in return, the insects produce sugars for the ants to eat. This is like humans milking cows or collecting chicken eggs. This might be one of the only other examples of husbandry by any other animal besides humans.

Argentine ants are a menace for other ant species they come across as they invade new lands. As they displace and remove other ants from their native lands, the Argentine ants are disrupting entire ecosystems. By displacing other ant species, they are removing food sources from other animals that rely on those ant species as their source of food. They can also have a direct impact on agriculture as well. By protecting aphids and scale insects they are hurting crops of nearby farmers. Aphids and scale insects are pests that eat crops.

If we want reverse the trend of the invasive Argentine ants then we must do something about it ourselves. One possible way to remove these ants is to introduce the phorid flies to areas where Argentine ants are a problem. This has already been done in Texas where they introduced similar flies to the area to deal with the fire ant problem. This strategy however could be a very dangerous thing to do. As often the case, introducing an invasive species to deal with another invasive species can backfire very easily. The phorid flies could start parasitizing other native species as well and this could be disastrous.

References

Suarez AV, Holway DA, Case TJ. (JAN2001). Patterns of spread in biological invasions dominated by long-distance jump dispersal: Insights from Argentine ants. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol. 98, 1095-1100.

Holway DA. (JAN1999). Competitive mechanisms underlying the displacement of native ants by the invasive Argentine ant. ECOLOGY, Vol. 80, 238-251.

Science Daily. September 29th, 2006. Fire Ant-Attacking Fly Spreading Rapidly in Texas. http://www.sciencedaily.com/releases/2006/09/060927110742.htm

Military bases as wildlife havens

2010-03-09T05:15:00.000-08:00

Military bases across the nation are serving dual purposes: defense of our nation and as wildlife refuges. I recall that some of the first surveys of military bases were being done when I was a graduate student at the University of Oklahoma during the late 1980's and early 1990's. Twenty years later, the bases are helping endangered species to increase population sizes.

The New York Times posted a video clip highlighting the efforts going on at Eglin Air Force base in Florida. Click here to see the video.

When bad things get worse: Invasional Meltdown

2010-03-08T12:17:00.000-08:00

Contributed by Sarah Cusser

Alien plants can be a big problem in natural environments. These out of place plants often encroach on areas preferred by natives. Once settled, they compete with neighbors by hogging food, water and space, leaving little for the local guys. Potentially, they can alter fire regimes, soil chemistry, hydrology, and threaten the very wellbeing of entire native plant populations. A successful plant invasion can change the structure of whole plant communities and often result in the loss of biodiversity.

Now imagine that these pushy plant invaders are not only showing up, but also bringing friends! These friends, along with hogging resources and space themselves, return the favor to those that helped them, reaffirming a relationship that facilitates further invasion. Once taken hold, this type of invasion cycle can be disastrous to ecosystems. This is the basic idea behind the theory of ‘Invasional Meltdown’.

Described originally by scientists Van Holle and Simberloff in 1999, the theory of “Invasional Meltdown” states that some alien species interact to facilitate others, creating a cycle that eventually benefits both invaders (1). How exactly invading species ‘return the favor’ and create these mutualistic relationships can take different forms. Some aliens consume or suppress native species that would otherwise predate upon fellow invasives. Some invaders produce resources such as food or shelter that are important for newly arrived invaders. Some invaders even go to the extent of reconstructing aspects of the physical environment to make it more hospitable for further invasion. And some invaders support their friends in more direct and intimate ways like the beneficial mutualisms of seed dispersal or pollination.

A good example of this last type of interaction was explored by a group of scientists lead by Dr. S. R. Simpson in 2005 (2). His team examined how the invasive honey-bee, Apis mellifera, was promoting the success and spread of the invasive shrub, Scotch Broom, Cystisus scoparius, in Australia. Scotch Broom is a highly invasive plant that causes serious problems across the globe. Introduced in Australia in the 17th century as a soil stabilizer and hop replacement in beer, the shrub has been amazingly successful in a variety of environments, and is known to prevent native plant restoration and harbor feral pests. The interesting shape of the shrub’s flower requires bees for successful pollination and seed set. In its European homeland, Scotch Broom takes advantage of large bees to move its pollen from plant to plant. In return, the bees get a meal of nectar and some extra pollen for their young. In the shrub’s expanded Australian territory however, bees large enough to pollinate the plant don’t naturally exist. So the question is, how does Scotch Broom manage to invade and reproduce at all in this foreign bee-less land? The answer that Simpson and his team suggest lies in the context of “Invasional Meltdown”.

At the turn of the 19th century, European honey-bees were introduced to the Australian continent. These large bees aren’t too picky in their diet and will visit native and non-native plants alike, including Scotch Broom. Dr. Simpson’s research was able to show that European honey-bees were responsible for 84% of the shrub’s seed set, which equates to a whopping 6000 seeds per day made possible by honey-bees! It’s clear from his work that Scotch Broom owes much of its success to the mutualistic relationship it has with its fellow invader, the European honey-bee. With this understanding, the research team is urging policy and management makers across Australian to consider incorporating the elimination of feral European honey-bees into the control of Scotch Broom. The team hopes that with the control of honey-bees, the alien shrub will also lose its momentum, putting an end to the invasion cycle, preventing meltdown, and diverting disaster.

Picture 1: The flowers of Scotch Broom have an interesting mechanism that prevents small bees from reaching its pollen. When pushed hard enough the keel, in the middle of the flower, opens to expose the pollen structures. Small bees simply don’t have the strength to push through the modified petals and reach the inner pollen.

Photo Credit: Wikimedia Commons

Picture 2: A European honey-bee, strong enough to reach the pollen of Scotch Broom.

Photo Credit: Wikimedia Commons

References

1. Simberloff, Von Holle. Positive interactions of nonindigenous species: invasional
meltdown? BIOLOGICAL INVASIONS. 1 (1) : 1387-3547 MAR. 1999.

2. Simpson, SR; Gross, CL; Silberbauer, LX. Broom and honeybees in Australia: An alien liaison. PLANT BIOLOGY, 7 (5): 541-548 SEP. 2005.

How humans are lending a helping hand to invasive species

2010-03-08T11:44:00.001-08:00

Contributed by Kyla Ferguson

Throughout history humans have had a large impact on the environments they live in, especially in today’s world when the loss of biodiversity is considered. The introduction of invasive species is one major universal change that has contributed to the decrease in biodiversity. Humans have been the transporters of many species that have become invasive, introducing many non-native species for reasons such as agriculture, horticulture and pet ownership. However humans are now considered as more than transporters; they are also seen as facilitators who help invasive species to prosper in new habitats.

An invasive species is a plant or animal that is not native to an area in which it is living. They are often viewed as aggressive because they grow and reproduce rapidly, limiting the amount of resources left for the native organisms. Invasive species are a major cause of ecosystem disturbance, which can lead to a decrease in the types of organisms found in the area. One way this occurs is through genetic homogenization of the biological diversity. This means that the new species are able to breed with the native species creating hybrid offspring. This reduces the number of native organisms and results in genetic swamping of native species genes with those of the invader. Biodiversity may be lost through extinction of native species as a result of the activities of the invasive species.

Humans facilitate invasive species by first bringing them to new habitats and then creating environments that allow them to thrive. These ideas have recently been studied using the American bullfrog as a model. The American bullfrog (Rana catesbeiana) is currently displacing the native threatened California red-legged frog (Rana draytonii). It was suspected that human interactions with the landscape such as the building of roads and their effect on the circulation of fresh water resources were playing a role in the bullfrog invasion.

American Bullfrog

Red-legged Frog

D’Amore et al. (2009) conducted a number of surveys over a three year period on both the frog populations and the surrounding areas. To determine the size of the frog population, night time eye shine surveys were conducted. Reproduction surveys were also conducted. These included net fishing to observe the number of larvae and listening surveys during the proper mating periods to record the occurrence of mating calls within a site. The pond water was also tested for nutrients, quality, and total area covered. Surrounding areas were also surveyed for agriculture fields, paved roadways, buildings, and other nearby wetlands. With the data collected from these surveys over a three year period the group was able to determine similarities between the study sites.

Statistically significant results showed that human alteration of the environment was favoring the bullfrog over the red-legged frog. One way humans are helping the bullfrog to displace the red-legged is by creating ponds that are full year round. This is required for the bullfrog to survive, but the native red-legged does not require this. Therefore an overlapping niche is being created that leads to more competition for space between the species. Also the breeding of the red-legged frog was found to be affected negatively by close proximity to roads or agricultural fields, even if adult frogs were able to live in the pond. However the bullfrog was found to be able to breed in any of the ponds the adults inhabited. This allowed for the occupancy of the bullfrog to remain constant in the ponds over the three year study; however the sites where the red-legged was found during the study varied from year to year with human activities in surrounding areas.

A clear correlation of human activity and occurrence of the bullfrog is seen in this study. It is likely that this correlation occurs for other animal and plant species as well. Therefore, in order to preserve biodiversity and control invasive species it is important that humans look deeper into their interactions with the environment. This may include researching the wildlife within a site that is under consideration to be altered to determine if the alterations will affect their needs or provide the necessities for an invasion (i.e., an environmental impact assessment should be done). Perhaps nature reserves can be set aside for the native species. Ultimately, our alterations on the environment should be more planned and well-informed of native species of the area than they have been in the past.
Reference:

D’Amore Antonia, Valentine Hemingway, Kerstin Wasson. 2009. Do a threatened native amphibian and its invasive congener differ in response to human alteration of the landscape? Biological Invasions. 12(1): p 145-154.

Images from Wikimedia commons

The economic toll of invasive species

2010-03-04T10:19:00.000-08:00

Contributed by Brandon Little

Satellite view of the North American Great Lakes region. (photo courtesy of Wikimedia Commons)

The Great Lakes are one the largest reservoirs in the world with approximately 20% of the world’s fresh water contained within them. According to the US EPA the Great Lakes account for more than 90% of the surface freshwater in the U.S., with a total shoreline of over 10,000 miles. The region is home to over 25% of the Canadian population and one tenth of the American population.

The Great Lakes have always been one of the great industrial engines of growth for the United States. From the advent of shipping and the construction of the canal system we have been utilizing the Great Lakes for much of the commercial transactions of the Midwest. In fact, more than 50% of total U.S. manufacturing output travels through them. This has led to an economic boom for the region and an ecological travesty. It is estimated that the Great Lakes are economically worth $200 billion dollars annually, with $4.5 billion coming from both commercial and sport fisheries. There is also a thriving boating economy with over 3.7 million boats in the 8 Great Lakes states (over 1/3 of the total in the United States). The Great Lakes national parks receive approximately 250 million visitors a year, which equates to untold economic value in the communities surrounding the Great Lakes region.(USEPA)

Invasive species have long been a problem in such a congested shipping lane, and the documentation of the first invasive species goes back as far as 1859. In modern times, with the advent of globalization, there is a continuous influx and outflow of traffic from most of the world going through the Great Lakes region. Modern ships utilize water instead of bricks as ballast and this has led to the introduction of the zebra mussel (Dreissena polymorpha). Zebra mussels were likely introduced to the Great Lakes region around 1988, were first observed in 1990, and now they are the most prolific invader of the Great Lakes region. Zebra mussels can produce up to a million offspring per year and can colonize any stable surface. This can include concrete, rocks, pilings, and even other native species of mussels. Once established they are impossible to get rid of and alter the entire structure of ecosystems. (WDNR)

Zebra mussels covering a current meter near Michigan City, IN (Lake Michigan; photo courtesy of Wikimedia Commons)

Since zebra mussels were introduced 20 years ago they have continuously filtered the water for nutrients and phytoplankton. This has increased water clarity from 3 feet to over 30 feet, and the zebra mussels have filtered out significant amounts of toxins which means light can penetrate much further than usual. This has allowed for a greater increase in algae growth, which in turn has altered the fish composition within the Great Lakes. By filtering the lake, zebra mussels directly compete with fish at the bottom trophic levels utilized for food by predatory fish. This has led to an overall decrease in both forage fish and game species, which as had a negative impact on fisheries. This may soon be coupled with the double punch of the Asian carp invasion.(WDNR, USGS)

Flathead and Silver carp were introduced into fish farms to help filter out waste products of other fish. This was a very effective system for fisheries until several floods released 5 species of Asian carp into the Mississippi river system. Asian carp had evolved in China to quickly outgrow predation, as a result, when released into the American waterways without significant predation, their populations exploded. Asian carp are filter feeders that extract nutrients and phytoplankton from the water. They directly compete with shad, a native forage fish. Not only do the Asian carp decimate the shad populations they also destroy the “game” fish populations which prey on shad. Silver carp also pose a serious threat to boaters because when disturbed they jump out of the water and have been responsible for many broken bones, blackened eyes, bruises, and even significant boat damage. (USGS)

Silver carp forage for food just below the water surface (photo courtesy of Wikimedia Commons)

Currently the US EPA has spent millions of dollars to prevent the Asian carp from entering the Great Lakes including building an electric net across the St. Lawrence river to prevent fish swimming upstream. Recently another $78.5 million has been proposed to further contain the spread of the Asian carp, but the proposal comes from the federal government and contains mostly half-measures and nonsensical propositions. Instead of closing the lock system they want to shut it 4 days a week, but fish don’t know or care what day it is and very well could make the transition any day. The true dilemma is that it will only take one fisherman and one wrong species identification to dump the carp into the Great Lakes despite of all preventative measures.(Hood)

What happens when the filter feeding fish and zebra mussels inhabit the same water in direct competition with native forage fish? No one knows, but the predictions are dire. The combination of such pressure on phytoplankton is almost certain to make the forage fish populations crash which will work up to every trophic level in the Great Lakes. Most experts expect at minimum a catastrophic drop in fisheries production and a significant decrease in recreational boating because of jumping silver carp. This will result in untold billions lost for fisherman, marinas, companies, states, and the entire region. One economist predicted at minimum a loss of $50 billion dollars a year due to two invasive species, a high price to pay for globalization.

Wild Jumping Carp On the Illinois River

Works Cited

Hood, Joel; Skiba, Katherine. “Asian Carp has price on its gills.” Dispatch Politics. 2010. Columbus Dispatch. 2/20/2010.

United States Environmental Protection Agency. “Great Lakes strategy 2002- A Plan for the New Milennium.” 2002. USEPA. 2/18/2010 http://www.cpa.gov/glnpo/gls/

United States Geological Survey. “Nonindigenous Aquatic Species.” 2009. USGS. 2/18/2010 http://nas.er.usgs.gov/queries/factsheet.asp?speciesID=551
http://nas.er.usgs.gov/queires/factsheet.asp?speciesID=549

Wisconsin Department of Natural Resources “Invasive Species-Zebra Mussels (Dreissena polymorhpa).” 2004. WDNR. 2/18/2010 http://www.dnr.state.wi.us/invasives/fact/zebra.html

The Savior and the Monster: Nile Perch

2010-03-01T09:11:00.000-08:00

Contributed by Andy Yoak

The Great Rift Lakes of Eastern Africa are home to one of the worlds greatest assemblages of animal life on the planet. Much of the fauna there is so exotic, that 200 species of fish are found in one lake and no where else. Lake Victoria is the clearest example of human impact on the area, with some great successes and abysmal failures in management of natural resources.

In 1954, the British colonial authorities in Uganda wanted to establish a profitable fishery in their colonial holdings. Lake Victoria was the prime candidate, straddling the borders of their protectorates in Tanzania and Kenya. But the local fisherman only pulled the small fish from the family Cichlidae out of the waters. Most of these fish are small, under six inches, and produce only enough flesh to be a local food crop. To be profitable venture the colonialist needed to increase the lake’s production somehow. The British found their cash crop in the Nile Perch, Lates niloticus, from the Congo and Nile rivers, which grows up to 4’6’’ and 530 lbs. The first introduced fish did well and established a population, which fed a small fishery industry. The local economy was making money, providing for sustained job growth, and the lake’s ecology seemed to be relatively stable. This equilibrium ended in 1983 when a change in the lake allowed the population of perch to boom exponentially.

Nile Perch - comparison of size to human (image courtesy of Wikimedia Commons)

The perch had succeeded in completely replacing the local fishes and now the local fishery was solely based off of just a few species. This was initially hailed as a boom to the economy, massive foreign investment followed and soon cargo planes were making daily trips to and from European destinations. Changes in the lake’s diversity carried a double edge for the fisherman however. The Nile Perch is a much stronger swimmer and will easily break through locally made plant fiber nets forcing the fishermen to buy expensive foreign-made polymer nets. The native fishes could be laid out in the sun to dry, but because of its high oil content in it’s skin, Nile Perch must be smoked or they will rot before ever reaching market. This has caused a cascading effect on the local environment. As more fires must be built to smoke the fish, the area is being deforested rapidly. There is growing concern that the planes who take away the fish do not bring anything back to give back to the area. Even more serious accusations have accused the planes of returning filled with weaponry to fuel the continents ever-simmering conflicts from their main destination, Russia.

The food chain has been broken down by the introduction of the Nile Perch. Where once an incredibly diverse collection of aquatic species populated Lake Victoria, now perch and the invasive species Nile Tilapia, Oreochromis niloticus, make up nearly 95% of the fish caught in the lake. Nearly all of the native cichlids have been driven to extinction by the perch. This has allowed a shrimp that normally was eaten by the cichlids to overpopulate and outcompete all the other lake invertebrates. Now the large perch feed on smaller perch, who consume Tilapia, who eat the shrimp. This is an incredibly tenuous arrangement. All that needs to happen is for a disease to wipe out one link from the chain, and the entire lake fish population will crash.

All the while, the human population surrounding the lake continues to grow and put more pressure on the lake’s resources. Thirty million people crowd the shores looking for work in the faltering fishery, most living in squalor and making $250 per year. The Nile Perch has brought jobs and foreign money, but how long will it last? And when the system finally fails, how different will the lake look compared to just 40 years ago?

References:

Kees, P.C. et al. “ The invasion of an introduced predator, Nile perch (Lates niloticus, L.) in Lake Victoria (East Africa): chronology and causes” Eviromental Biology of Fishes 2008

Mailu A.M. “Preliminary assessment of the social, economic and environmental impacts of water hyacinth in the Lake Victoria basin and the status of control” ACIAR Proceedings 2001

The undiscovered species in your backyard

2010-02-26T11:23:00.000-08:00

Contributed by Samuel Bolton

When prompted to think of how newly discovered species are found, most of us imagine an intrepid adventurer braving a difficult and dangerous journey into the depths of some hot and steamy jungle. But within the last few years more and more evidence is indicating that even the best studied and most accessible places in the world harbor a greater number of unknown species than we had previously thought possible.

Until recently, most scientists studying tiny organisms (those life forms that are less than a fifth of a centimeter big) believed that they were so abundant that every species had the tendency to get everywhere (1). A scientist undertaking an inventory of these organisms was, therefore, expected to compile more or less the same list as one who was undertaking an inventory from a completely different part of the world. It is true that these inventories have often been quite similar and that, for this reason, it was assumed that most of the species of tiny organisms had already been discovered. But these similarities were based on the supposition that organisms that looked the same were the same. However, recent research into the DNA of a number of different kinds of tiny organism is revealing a previously hidden diversity of many new species.

Tiny organisms have always been difficult to identify due to their small size and simple body plans. In contrast with the larger animals and plants, their DNA tends to be very variable relative to their shape and form. Therefore, a tiny organism that is outwardly indistinguishable from many other species can have such dramatically different DNA that it needs to be classified as a new species. Splitting up species using only their DNA may seem akin to splitting hairs. But consider that bacteria that cannot be told apart from other bacteria using any visible features under a microscope have often been lumped into the same species if more than 70% of their DNA is identical. If we were to apply such a strict and conservative criterion to mammals we would likely find that all of the primates (which include monkeys, apes and lemurs amongst other groups) belong to a single species (2).

Rotifers have been split up into many new species on the basis of their DNA. They were previously thought to comprise much fewer species because their shape and form is not sufficiently variable enough to distinguish them.

Source: The Micropolitan Museum, © Wim van Egmond.

With the recovery of DNA from more and more tiny organisms, species that were once thought to be distributed across the whole of the world have been shown to comprise multiple species that are restricted to specific regions or continents. For example, one group of scientists (3) has recently discovered such a pattern of limited distribution for many new species of rotifer (an extremely small type of animal with a very primitive and basic body plan). Prior to this investigation, a significantly smaller number of species had been recognized in their place due to the difficulty of describing new species of rotifer using only their visible features. One of the latest studies by the same research group (4) has now revealed a new and unexpected twist that may yet prove to be broadly applicable to most other types of very small organisms. This revelation relates to the way in which many kinds of tiny organisms reproduce without sex by instead creating identical copies of themselves.

Sexual reproduction ensures that the members of a species are continually exchanging their DNA with one another in order to produce offspring. Accordingly, any particular lineage (line of descent) within a species can seldom, if ever, accumulate a very distinct set of DNA if it resides in the same place as other lineages that belong to the same species. For this reason, there can be little or no opportunity for the divergence of species (the process whereby a single species evolves into two or more distinct species). But because many tiny organisms reproduce without sex, they do not exchange DNA with other members of their species during the descent of their particular lineage. They are, therefore, able to accumulate enough differences in their DNA that a single species can, given sufficient time, diverge into many new species without having to occupy new and separate places.

Although it is perhaps not that surprising that reproducing without sex has, therefore, lead to the evolution of new species, the dramatic pace with which this has occurred for rotifers has not been anticipated. Consequently, not only has it been shown that numerous species of rotifer break down into multiple new species in accordance with the different parts of the world in which they live3, but they have now been able to further subdivide them into a much greater number of species that inhabit the same places and habitats4. Many of these newly discovered species were found in what have historically been the most intensively researched and surveyed countries in the world. For example, one species could be shown to split into 24 new species in Britain alone. Up until that point, nobody had gotten around to examining its DNA. As a large proportion of the different types of tiny organisms contain many species that are known to reproduce without sex, it is unlikely that rotifers are unique amongst them in their capacity to diverge into so many different hidden species within the same place.

Even the African Elephant has been split up into two different species on the basis of its DNA. If such large and complex organisms can be shown to comprise previously hidden species, we can only speculate about the numbers of small and tiny species that await discovery.

Source: Commons.wikimedia.org, © Calle v H

But being a hidden species is not the sole preserve of the tiny. One of the more startling outcomes of the DNA revolution is that species have been split up into new ones within almost every size category of organism, up to and including elephants5. With such a great amount of unknown diversity out there that can only be detected in this way, it is anybody’s guess as to the true number of species on this planet, just as long as that guess is a very big number. What we do know is that we have only extracted and studied the DNA of a very small proportion of species described from their shape and form alone. And as this traditional method of defining species is still a very short way into a complete inventory of Earth’s visibly different living things, the task of discovering every last hidden species from its DNA is a truly mammoth one. The scientists that have only barely begun it are now rapidly gravitating towards a consensus that there are undiscovered species living in your backyard.

References

1. Finlay, B. J. (2002) Global dispersal of free-living microbial eukaryote species. Science, 296, 1061-1063.

2. Staley, J.T. (1997) Biodiversity: are microbial species threatened? Current Opinion in Biotechnology, 8, 340-345.

3. Fontaneto, D., Barraclough, T. G., Chen, K., Ricci, C. & Herniou, E. A. (2008) Molecular evidence for broad-scale distributions in bdelloid rotifers: everything is not everywhere but most things are very widespread. Molecular Ecology, 17, 3136-3146.

4. Fontaneto, D., Kaya, M., Herniou, E. A. & Barraclough, T. G. (2009) Extreme levels of hidden diversity in microscopic animals (Rotifera) revealed by DNA taxonomy. Molecular Phylogenetics and Evolution, 53, 182-189.

5. Roca, A.L., Georgiadis, N., Pecon-Slattery, J., O'Brien, S.J. (2001) Genetic evidence for two species of elephant in Africa. Science, 24, 1473-1477.

Why is the weed in my yard spreading?

2010-02-23T13:20:00.000-08:00

Contributed by Jeff Rose

Have you ever wondered about that shrub with pretty white flowers growing in your backyard? It could be an invasive non-native shrub species. Lonicera mackii (Amur honeysuckle) was introduced as an ornamental shrub from Asia about a century ago, and was widely available from nurseries about 80 years ago(3). Although several species of honeysuckle are native to North America, including Ohio, they are mostly vines. The first reports of Amur honeysuckle as an escape in Ohio were a mere 50 years ago in the Cincinnati area. Since then, honeysuckle has proliferated to become one of the most common and familiar forest invaders in urban and suburban landscapes. Honeysuckle flowers in the spring and produces bright red berries in the fall which are spread by songbirds, such as the familiar American Robin (Turdus migratorius), though recent studies have shown that honeysuckle may also be spread by small mammals and even white-tailed deer (Odocoileus virginianus;1)! Studies have also shown that honeysuckle acts to shade out native tree and wildflower species, decreasing their ability to survive and reproduce which poses long-term consequences for the composition of woodland habitats(2). The rapid range expansion of this species has prompted scientific study into the cause of this spread, specifically as to the reasons for its spread, the consequences of its spread, and control of its spread.

In a recent study on the causes of the spread of honeysuckle by Goodell et al. (1), the effects of pollen limitation on this plant were investigated. Pollination of honeysuckle is mediated by insects, most of which are bees. For an insect-pollinated plant to become established, it is important that pollinators visit it, some of which may be native pollinators who have co-evolved with native wildflowers. This can cause native insect-pollinated plants to suffer in reproductive ability, depending on how much of the pollinator resource the invasive plant takes up. It is also important (generally) that a plant reproduce with other individuals so that its offspring do not experience negative effects of inbreeding. Therefore, an invasive plant may be limited in its reproductive success by the amount or type of pollen it receives. A plant may be pollen limited for several reasons. It could be that not enough of the right pollinator is visiting the plant, or it could be that no enough pollen from other plants is being deposited on the flowers. If a plant is not limited in its ability to reproduce and spread by pollen, then no effect of pollen source or pollinator visitation on reproduction should be observed. The effect of pollinator visitation and pollen quality was observed on honeysuckle flowers at the edge and in the interior of woodland habitats. In order to assess the amount of pollinator visitation, both the number of flowers visited and amount of pollen deposited on a flower was observed and the number of resulting fruits observed. To assess the effect of pollen quality, several flowers had pollen from other plants added to them, while others were left alone. Fruit set was then compared.

It was found that plants on the forest edge received more visits by pollinators, more visits per plant, and had more pollen deposition on the flowers than did plants in the forest interior. Insects preferentially went to sun-exposed flowers, possibly as a result of the fact that bees see in ultraviolet light. In addition, artificial addition of pollen resulted in higher fruit set. Additional pollen deposition can result in over a 100% increase in the ability of honeysuckle to reproduce! Since most birds that consume and subsequently disperse honeysuckle reside primarily at the forest edge, such as the American Robin, the cause of decreased honeysuckle reproduction in these habitats is of particular importance for understanding the spread of honeysuckle. The authors’ conclude that the reason for decreased reproduction in the more important edge habitat is pollen quality. That is to say, there is not enough pollen from other plants being deposited on these edge plants and there is decreased reproductive success because of inbreeding. By contrast, interior plants experience decreased reproduction because no enough pollinators are visiting them. Disturbance such as tree removal could result in increased light and therefore increased pollination and reproduction. With the proliferation of forest edge habitats, these weeds will only increase in their proliferation in your backyard.

References:

(1) Goodell, K., A.M. McKinney, and C.H. Lin. 2010. Pollen limitation and local habitat-dependent pollinator interactions in the invasive shrub Lonicera mackii. International Journal of Plant Sciences. 171: 63-72.

(2) Gould, A.M.A. and D.L. Gorchov. 2000. Effects of the exotic invasive shrub Lonicera mackii on the survival and fecundity of three species of native annuals. American Midland Naturalist. 144: 36-50.

(3) Luken, J.O. and J.W. Thieret. 1995. Amur Honeysuckle (Lonicera mackii: Caprifoliaceae): its ascent, decline, and fall. Sida. 16: 479-503

Extinction and colonization dynamics on forest patches

2010-02-20T17:02:00.000-08:00

Contributed by David Salazar-Valenzuela

Biodiversity remaining in forested areas around the globe faces challenges associated with the modification and management of the landscape by humans. Deforestation of natural areas changes the dynamics of biological communities inhabiting altered habitats. Species react to these alterations in different ways; some decline sharply or entirely disappear, others seem unaffected, and yet others increase in numbers. Given the complexity of these relationships, biologists have gained a better understanding of the dynamics of extinction and colonization by analyzing islands. Researchers assume that patches of forest formed by habitat fragmentation exhibit features reminiscent of insular environments. There are three general patterns shaping the structure of insular communities; 1) the number of species tend to increase with island area, 2) the number of species tend to decrease with island isolation, and 3) biological communities are constantly experiencing colonization and extinction.

Biologists with interests in the ecology, evolution and conservation of biodiversity in forest fragments have used these insights to try to determine if similar patterns hold in fragmented habitats. They have been especially concerned about the implications of these mechanisms on the occurrence of species in these habitats. One famous example of the adoption of insular patterns in fragmentation research was the debate of whether a single large reserve was preferred over several small reserves that covered the same area to protect species. Studies have shown that it depends on how well the small protected areas reflect the biota inhabiting the large reserve.

Earlier studies showed that compared with extensive contiguous areas, many species are absent from small and isolated patches. However, relationships appear not to be as straightforward as predicted insular patterns. In fragmented habitats, some but not all species disappear after isolation whereas others are rare in small patches irrespective of how isolated the habitats are. The effects that area and isolation have on the dynamics of extinction and colonization of fragmented habitats have been assessed by inferences deriving from patterns of species occurrence. Nevertheless, direct tests of these factors are scarce. The study by Ferraz et al. (2007) represents an experimental assessment of the effects of patch area and isolation on the assembly of an Amazonian bird community. Some of the strengths of this study are that researchers gathered data on relevant geographical (23 primary-forest patches ranging in size from 1 to 600 ha) and temporal (13 years of monitoring) scales. They established a mist-netting bird monitoring program on The Biological Dynamics of Forest Fragments Project, which is a long term study intended to test the effects of forest destruction at the patch level. Back in the late 1970s, this program was founded with the aim to test insular patterns of species richness on these fragmented habitats. They hypothesized that a reduction in forest area will lead to an increase of local extinction probabilities, and that the isolation of forest patches will cause a reduction of species colonization probabilities and an increase in local extinction.

Based on the occurrence data of 55 species of birds on the different monitored patches, the researchers tested 15 hypotheses that varied as a function of four parameters: initial occupancy of a species, a local extinction probability, a local colonization probability, and a detection probability given the presence of the species. The models were analyzed and the best fitting ones were interpreted for each species. The authors found that several associated factors (e.g. isolation, patch size, forest regrowth) contributed differently to colonization, extinction or both in regard to each species. Focusing on only the best model weighted across species and on the best-fitting model for each species, researchers found that a substantial proportion of species is not significantly vulnerable to isolation, but that they are highly sensitive to area.

In conclusion, this study empirically demonstrated that, even though there is interspecific variation in the rates of extinction and colonization, there is a strong area effect in shaping these parameters. While this general pattern supports the importance of larger reserves to protect species that are highly sensitive to area, the variation of interspecific response highlights the role that small reserves scattered across a region could have in protecting some other species. Additionally, while the effect of isolation on rates of extinction and colonization were found to be less obvious than the area effect, the authors warned that this study was conducted on a landscape dominated by forest and that a more intensive modification of the Amazon tropical forest might reflect a larger effect of isolation.

Certainly more research is needed in order to clarify the establishment and persistence of biological communities on fragmented habitats. Even though, a great deal of knowledge has been gained from comparison to biotas inhabiting islands, forest fragments appear to exhibit their own characteristics that may prove to be even more complex than strict insular habitats.

For more information, see: Ferraz, G., Nichols, J. D., Hines, J. E., Stouffer, P. C., Bierregaard, R. O. and T. E. Lovejoy. 2007. A large-scale deforestation experiment: Effects of patch area and isolation on Amazon birds. Science 315 (5809): 238-241.

Images courtesy of Wikimedia Commons

Effects of a warmer world on our seasons

2010-02-19T08:44:00.000-08:00

Contributed by Kellen Calinger

The changing of the seasons is a natural part of many peoples’ lives as we wait for the first hints of green to appear on the trees in the spring and look forward to the beauty of the autumn colors. Although many of us watch these events unfold with little thought to any greater importance, the study of phenology, or the timing of key life events, is attracting renewed attention as it is an important indicator of climate change.

Phenology involves not only events like leaves changing colors and dropping in the fall, but also describes occasions like animals entering into and ending hibernation and pollinators beginning their work in the spring. The timing of phenology is regulated by either changes in light conditions or temperature as we move through the seasons. Under natural conditions, plants and animals are synchronized with these environmental cues, and are able to either leaf out or end hibernations at the right time—that is, after any dangerous cold weather but as soon as enough food or light is available. However, the burning of fossil fuels has released huge amounts of carbon dioxide (CO2) into the atmosphere and is causing significant increases in temperature. For plants and animals that rely on temperature cues for their seasonal activity, this temperature change may alter their functioning in the environment.

We already have convincing evidence that human-caused temperature increase is greatly altering the functioning of forests in the northern hemisphere. Two landmark studies by Keeling et al. (1996) and Myneni et al. (1997) highlight the extent to which climate change is already impacting the phenology our northern forests.

The first article was written by a team lead by scientist Charles Keeling, famous for his well known Keeling Curve. The Keeling Curve is a graph of CO2 levels measured at Mauna Loa Hawaii starting in the 1960’s and continuing to the present. This data is particularly important because it was some of the first clear evidence that humans are causing increased CO2 levels in the atmosphere as a result of fossil fuel burning. Along with telling us that CO2 levels are rising at a very fast rate, CO2 measurements also showed us that there is a yearly pattern of CO2 concentrations with the highest levels in the winter and the lowest in the summer. The reason for this annual pattern is photosynthesis. Plants perform photosynthesis to make sugars, or food, and they have to absorb CO2 to do this. As a result, during the summer when plants have their leaves, they are sucking in lots of CO2 and the levels of CO2 in the air decrease. Then, in the fall when plants lose their leaves, they can’t do photosynthesis and absorb CO2, so levels of CO2 in the air increase again in the winter until the leaves come out in the spring.

The team of scientists led by Keeling used this yearly pattern of CO2 measurements to find out if there have been any changes the phenology of forests at two locations; Mauna Loa, Hawaii and Point Barrow, Alaska. At both study areas, scientists found that plants currently are drawing down more CO2 in the summer months than they were in the 1960’s. Not only are they absorbing more CO2, they are starting to pull the CO2 in their leaves a full week earlier (as of 1994) than in the 1960’s! So what does this mean? Since the time of CO2 decrease is much earlier in the spring now, we can tell that leaves must be coming out earlier and starting photosynthesis much more quickly. This means that our growing seasons are getting longer as a result of higher temperatures causing plants to get their leaves more quickly. This data also shows us that our forests’ phenology has already been very impacted by human activities through higher temperatures. Knowing this is very important, because if plants get their leaves more quickly in the spring, our forests may be able to pull in much more CO2, and this knowledge is critical as scientists try to predict the effects of global warming in the future.

The next paper, by Myneni et al. (1997) gives us more direct evidence that leaves are coming out earlier in the spring, that is, that phenology of our forests is changing. This team of scientists used a type of data called Normalized Difference Vegetation Index (NDVI) taken from satellite pictures. This data shows how light is reflected off of leaves, and in this way, can tell us how much photosynthesis is occurring in forests. Based on the results from Keeling’s CO2 study discussed above, we would expect higher NDVI, or more photosynthesis, earlier in the year at both study sites. Myneni’s team of scientists found much higher NDVI values in both Hawaii and Alaska showing that higher temperatures are indeed causing more photosynthesis. Along with this, the scientists found a roughly 8 day advance in spring time and a 4 day delay in the fall. If we add these values up, we can see that the growing season has had a total lengthening of about 12 days! These changes show us very large shifts in phenology are already occurring and that they are happening across a very broad region of the northern hemisphere.

The take home message from both of these papers is that by burning fossil fuels that release CO2 into the air, humans are warming Earth and are already significantly changing how our forests function. Both of these studies provide convincing evidence that higher temperatures have caused shifts in phenology with spring happening earlier and fall occurring later. This knowledge is very important for predicting how much CO2 we can expect forests to absorb and therefore is also needed to predict how serious the impacts of global warming may be in the future. The message of these papers is also one of caution in that the effects we saw were much larger than those predicted using models. In short, our ecosystems’ phenology is responding much more strongly to higher temperatures than we expected. Thus, it is extremely important that we begin to take steps to lower CO2 emissions in hopes that we can prevent, or at least moderate, additional potentially negative effects of global warming.

References:

Keeling, C.D., J.F.S. Chin, and T.P. Whorf. 1996. Increased activity of northern vegetation inferred from atmospheric CO2 measurements. Nature. 382: 146-149.

Myneni, R.B., C.D. Keeling, C.J. Tucker, G. Asrar, and R.R. Nemani. 1997. Increased plant growth in the northern high latitudes from 1981 to 1991. Nature. 386: 698-702.

Images from Wikimedia Commons except where noted.

Increasing Urban Sprawls Evict Biodiversity

2010-02-17T09:50:00.000-08:00

Contributed by Tim D. Malinich

Human beings may be one of the most influential organisms on the planet. The potential of our impact has almost no limits, and we are only just realizing this fact. Scientists now agree that humans are the main cause of the 6th and most recent mass extinction of many organisms that once lived upon our planet. Our impact on the diversity of life will have tremendous effects on the planet and on our own existence. It is crucial that we understand the anthropological effects of our growing influence and through this understanding work to protect the remaining diversity of life.

Critical to the protection of biological diversity is the conservation of biodiversity hotspots. These are regions that contain a high amount of species diversity and richness in a small but geographically important area. The known hotpots cover approximately 1.4% of the Earth’s surface, hold nearly 44% of the Earth’s plants and over a third of its vertebrate species! Because these hotspot regions are constricted in size the species within are at high risk to a multitude of threats, many of them anthropological.

It has already been stated that humans have a negative impact on diversity. This impact comes in several different forms. Deforestation and climate change are among the most commonly mentioned forms of impact on biodiversity. It is easy to understand how the loss of habitat and the extensive ecological changes that accompany climate change can damage biodiversity hotspots. Also associated with biodiversity loss, is human population size and growth rate. Along with these impacts on biodiversity there is also the affect of household dynamics; that is the changes in household numbers and resource use. This household effect was studied by the Department of Fisheries and Wildlife at Michigan State University in 2003.

When household numbers decrease, referring to the number of people per home, there is a significant affect on biodiversity. When fewer people live within a household more households are built to accommodate the population. Each household requires more land and resource use. In addition, fewer people in more households means that there is a less efficient use of energy and resources. A simple example of this is to contrast the energy demand to heat up two different household scenarios; one house with four people or two houses with two people each. This trend is related to the per capita rate of income in a country and generally not its population growth. As the per capita rate of income increases homes become easier to afford by fewer people. This is a growing trend in countries with emerging economies such as India, China and Brazil. Other factors that may be contributing to the decline in household numbers may be lower fertility rates, increased divorce, and a decline in multi-generational families living together. Many countries that have decreasing populations will continue to have an increase in the number of households. For example New Zealand declined by almost 7,200 people but the number of households in this country increased in some regions by approximately 7,650 households.

Over 80% of 76 hotspot countries investigated showed a greater increase in household numbers than population growth. In non-hotspot countries, only 1.7% of countries appeared to show this trend. If this trend continues, it is expected to see an increase in households equal to 233 million households in hotspot countries, such as Italy, Portugal and Greece, between 2000 and 2015. This is a near nightmare to conservation in these regions. Each household adds to the consumption of resources, such as wood, that generally come from biodiversity hotspots.

Decreasing sizes of household inhabitants and increasing numbers of households already have a strong impact on hotspot regions such as Wolong Nature Reserve in China, regions in Brazil, and the Indian River County in the United States. It is important for conservationists to consider this strong effect when trying to develop strategies to preserve the remaining biological diversity on our planet. Not only must they consider traditional factors such as population growth and deforestation, they must also predict declining efficiency due to increased household numbers in developing countries.

For more information see; Effects of household dynamic on resource consumption and biodiversity by Liu, J., G. C. Daily, P. R. Ehrlich and G. W. Luck. 2003. Nature 421: 530-533.

Ecological footprint image courtesy of Wikimedia Commons. Biodiversity Hotspot Image courtesy of Conservation International

The Invasion of the Rusty Crayfish!

2010-02-16T07:05:00.000-08:00

Contributed by Tony Cleland

Species relocation is becoming easier with the increasing amount of trade across vast geographical regions. However, not all species being relocated succeed in surviving in their new environment. Of the lucky survivors, very few become invasive. The survival of non-native species often relies on their ability to adapt quickly to a new environment. While genetic variance may be an adaptation which leads to the long term success of a non-native species, many successful adaptations come in the form of physiological and behavioral changes. Unfortunately, the short term success of non-native species may also lead to the demise of the native species. In many cases, if the native species does not adapt quickly to the newly established diversity, then their numbers will decrease rapidly. This decrease may be due to an increase in predation, competition, a decrease in the amount of shelter, or to hybridization. In recently discovered cases, some species are able to maintain in the presence of invasive species. For example, an increase in predation leads guppies to increase production of offspring as well as produce offspring which are larger and that mature at a slower rate.

The prevention of the spread of invasive species has proven to be very difficult. In order to prevent the spread of invasive species, one must accurately predict the species which pose a threat to others in the surrounding areas as well as form an effective barrier which would prevent their spread. This barrier must take into account the surrounding life in the biota and, therefore, makes dispersal prevention of invasive species increasingly complicated. A somewhat effective way of habitat repair has come through efforts to eradicate invasive species. While eradication may be effective, many invasive species have already displaced or completely destroyed the native species population by the time the eradication effort begins. Nevertheless, the removal of invasive species from a habitat gives researchers a chance to study population and habitat restoration in real time as well as possible mechanisms which allow invasive species to become so successful in their new habitat.

A recent study has addressed the mechanism of species invasion by the rusty crawfish (Orconectes rusticus) into Sparkling Lake, an isolated lake in Wisconsin home to the solitary virile crayfish (Orconectes virilis). Crayfish relocation has led to the invasion of several crayfish habitats across the continental United States. In fact, the virile crayfish itself has been known as an invasive species in several Atlantic coastal states. This suggests that the virile crayfish is likely capable of rapid adaptation. In this case, however, the rusty crayfish proves to be the superior species in Sparkling Lake. After the introduction of the rusty crawfish to the region in the 1970’s, the virile crayfish population began to drop rapidly. Within a few years, there was almost no trace of the native virile crawfish in the lake. In 2001, a group of field researchers began to eradicate the rusty crawfish in the lake. Within a few years, the virile crawfish population in the lake grew and, eventually, researchers were able to pull virile crayfish from the lake with relative ease. The restoration effort appeared to be working. But one question remained. What was it that allowed these virile crayfish to survive decades of invasion by the rusty crayfish?

The group decided to perform a set of experiments in which they compared the behavior and growth of the virile crayfish native to Sparkling Lake, which they refer to as the experienced group, to that of virile crayfish which lived in surrounding lakes with similar shelter and predation, or the naïve group. These two groups of virile crayfish were then placed in a common shelter with rusty crayfish of the same sex and similar size. In one experimental set up, a rusty crayfish and a virile crayfish were placed in an opaque container filled with water from Sparkling Lake as well as suitable shelter. The behavior of both species was recorded according to three responses: Approach, Retreat, and Seek Shelter. Unsurprisingly, the rusty crayfish were more aggressive and likely to approach the virile crayfish while the virile crayfish were more likely to retreat. One striking difference in behavior occurs between the naïve virile crayfish and the experienced. It seems that the experienced virile crayfish were significantly more likely to seek shelter than the naïve crayfish. This may suggest that the virile crayfish living in Sparkling Lake have adapted to a decrease in the relative amount of shelter in the lake and have changed their behavior accordingly. They are more aggressive than the naïve crayfish when searching for shelter. This may be what gives them a slight competitive edge over the rusty crayfish when avoiding predators and it may be what allowed them to exist in the presence of an overall more aggressive rusty crayfish.

Another study performed addresses the growth of the crayfish in a simulated habitat, called a mesocosm. This study placed naïve and experienced virile crayfish, four at a time, in a mesocosm with four rusty crayfish. The researchers varied the amount of shelter and food in the mesocosms. At low levels of food and shelter, the virile crayfish experienced difficulties growing. Overall, however, the experienced crayfish exhibited positive growth while the naïve crayfish experienced a decrease in growth. This furthermore strengthens the suggestion that the crayfish in Sparkling Lake under went some kind of adaptation after living for several years in the presence of the rusty crayfish. While this change is thought to be only behavioral, it has yet to be determined whether or not there are genetic factors also playing a role. If so, it would be a great example of evolution in real time. If genetic factors are not involved, the case of the virile crayfish will still serve as a positive example of resistance to invasion and give scientists insight on how to preserve native species populations.

Reference:

Hayes, Nicole M., Butkas, Katrina J., Olden, Julian D., Vander Zanden, Jake. (2009) “Behavioural and Growth Differences Between Experienced and Naïve Populations of a Native Crayfish in the Presence of Rusty Crayfish.” Freshwater
Biology. 54, 1876-1887.

Conservation concerns for sturgeons

2010-02-11T08:23:00.000-08:00

Contributed by Dan Robarts
The path of human expansion across the globe has left the natural habitat of many species fragmented or destroyed, leading to extinction in many documented cases. These impacts have become so overwhelming that many have taken up the cause to protect and rehabilitate the dwindling biodiversity of our planet. Describing the remaining variation found in populations and individuals can aid the understanding of conservable diversity, and help develop conservation and management practices.

One such threatened group is the fish family Acipenseridae, familiarly known as the sturgeons. This assemblage is made up of 26 globally-distributed species. The European races have been of significant economic value over the last few hundred years and today are known as producers of black caviar. Reproductive attributes are similar to salmon, in that they spend adulthood in saline and brackish environments, and swim upstream into fresh-water rivers to spawn in waters from which they originated. Unfortunately, an individual sturgeon may only reproduce a few times over the many years they exist, making population stability extremely susceptible to overfishing and habitat disruption.

Historically, sturgeons have been endemic (but not limited) to almost all major sea-bound river systems, but over time many species have become extinct due to unsustainable fishing practices. As modern refrigeration has developed, sturgeon have been increasingly sought for their prized roe, but its extraction, unfortunately, does not allow for survival of the harvested fish. Increasing demand has led to decimation of most European species, some with little hope of persistence. International agreements restricting the harvest of these fishes has not dissuaded many as single-fish yields of caviar can have value of over $3,000, making poaching a very serious threat to sturgeon survival.

There have been many recent studies exploring ways to follow and ameliorate the long-term effects of changes to genetic diversity in sturgeon after numerous attempts over the last two centuries to (re-)introduce these diminished fishes to various habitats. In many instances, these efforts have hindered regeneration of healthy sturgeon populations and have stemmed from a lack of understanding of the discrete differences between species. This intrinsic variation between groups of sturgeon can be best elucidated via highly resolved examination of the underlying biological mechanisms.

The blueprint that contains the directions and instructions for creation and functioning of all living things is the molecule known as DNA. Over the last 25 years, techniques have been developed to describe variation in this sequential code at ever increasing levels of detail. Current methods deciphering the cryptic, molecular variation can delineate between species and even individuals – acting like barcodes for the different groups. Development of processes that detect these genetic landmarks has been difficult for sturgeons, as different species have experienced very modest genetic change over their millions of years on the planet. Early DNA-based analyses for identifying sturgeon species provided limited information and were prone to false positives due to their ambiguous signals or human errors in data processing.

One of the most infamous issues arising from genetic markers in sturgeon relates to production of caviar. In order to protect against destructive harvesting practices, the CONVENTION ON IMPORTATION AND TRADE OF ENDANGERED SPECIES (CITES) lists endangered species that can be used for commercial products, and allows for confiscation pending appropriate identification. Caviar is frequently examined and traced to specific species, in order to ensure protection of sturgeon. Some species of sturgeon are easily and reliably identified by their DNA markers, such as the starred and beluga sturgeon (producing sevruga and beluga caviar, respectively), but the internationally accepted diagnostic test for Russian sturgeon has not proven to be infallible. Errors in species misidentification by fishermen and molecular analyses have led to government confiscation of tons of presumed illegal caviar. Also, the release of hybrid fishes arising from protected lineages has decreased commercial availability of caviar.

Genetic fingerprinting of species has become critical regarding the conservation of sturgeon. The mapping of interspecific relatedness, via phylogenetic trees, has traditionally utilized “neutral” molecular markers. This genetic sequence is not associated with heritable traits - therefore avoiding pressures of environmental selection and is randomly, and often maternally, inherited. These markers have been the standard for developing lineage hypotheses, but a growing body of work with very limited population suggests that patterns of variation and divergence in valuable adaptive traits are not well reflected by neutral markers. In order to save the sturgeon diversity, a paradigm shift is needed, with more of a focus on breeding for character traits that increase the fitness of sturgeon in today’s environment rather than exploring evolutionary questions.

Sturgeon populations have been impacted for hundreds of years, but in the last half -century we have been able to see the effects of these management efforts. Molecular analyses have found that many modern populations carry genetic material from geographically disjunct species, which is almost assuredly due to human involvement. With the release of “artificially” reproduced fish, there is the risk of irreversible genetic dilution via hybrid release and stocking.

Many modern conservation programs serve as breeding programs designed to select for valuable genetic diversity of threatened species. When trying to rebuild sturgeon populations from very limited numbers it is critical reduce the risks of inbreeding and outbreeding depression, and loss of diversity among populations. Release of captive-bred sturgeon is in critical need of monitoring to assure that fitness has not been lost due to the reshuffling of genetic material. Local genetic adaptations may be diluted with each successive generation in mating of genetically distant individuals, but this decline may not be apparent until the second generation or even later. Homogenization of genetic characters may leave these ancient fish without the ability to adapt to disease or changing environment.

Conservation efforts in sturgeon have been in place for centuries, but only with the advent of molecular marker techniques have significant gains been possible in preserving their diversity. If sturgeons are to persist, population management will be critical – from monitoring effects of captive-bred lines in natural environs to reducing poaching. Potential for increasing farm-raised fish for commercial applications may brighten the future of wild sturgeon populations, provided that these are properly managed and the endemic stocks are not contaminated.

For more information, see: Ludwig, A. (2006). A sturgeon view on conservation genetics. European Journal of Wildlife Research 52(1):3-8.

Photos from Wikimedia Commons

Understanding the Concepts and Importance of Population Ecology

2010-02-09T07:14:00.000-08:00

Contributed by Lucia Orantes

Let’s start by defining the basic terms of this field: population and ecology. A Population is a group of organisms (i.e. bacteria, plants, animals, etc.) capable of holding constant physical interaction. Since one of the main characteristics of a population is its ability to reproduce, a population can only be defined within a single species. On the other hand, ecology is the study of how organisms interact with their environment. All living organisms, including us, have to deal with environmental factors whether it is to find our source of food, coexist with other species, or adapt to natural elements such as weather or landscape. Population ecology exists to provide us with information on how a particular species reacts to an environmental event.

Changes in the environment have a profound effect on population dynamics, and so this field specializes on answering questions from the perspective of the populations affected, and not from the environmental point of view (there are other research specializations for this). For example, in a broad topic like climate change, population ecology investigates topics like the effect of global warming in a particular population of polar bears. In 2005 Dr. Andrew Derocher, from the University of Alberta, wrote a paper on a twelve year research study on how human and climate intervention has transformed the dynamics of a community of bears in Norway. When addressing the effect of climate he explained that, though it is very difficult to see the direct impact of climate on the bears, the increase in temperature has negatively impacted the number of seals (polar bears’ main prey) available as food source. Written from a population ecology viewpoint, the paper evaluated how this shortage of food can immediately change hunting behavior, the success of fattening up for winter hibernation, and the amount and quality of food for their cubs.

As in other biology related fields, in the past decade population ecology has been transformed by the application of molecular techniques. Many tools have been developed to analyze DNA for population ecology; the most common are called molecular markers. Literally we refer to marks in coding and non coding regions of DNA (hence the molecular connotation). These are taken from a large number of individuals from a population, and used to see if they persist along different populations of that same species.

Much of the molecular based research is focused on finding out if a characteristic that makes an organism more fitted to its ecosystem can be passed to next generation in the same or different population. Other studies analyze if isolation or fragmentation (separating big populations into small groups) can affect the ability of the species to survive or adapt in the ecosystem. Since molecular studies can gather large amounts of information about a species, they can be used as fundamental blocks for other disciplines such as conservation ecology, which implements strategies to maintain the population stability of a species in order to prevent extinction.

A good example of how molecular markers are used in population ecology is a study done by the University of Arizona based on small desert flies Drosophila spp. (Pfeiler and Markow, 2001). In summer Sonora Desert is such a harsh environment, that spaces where water and food are abundant are small and delimitated (resembling island systems). Such limitation also prevents the interaction among populations of a species, resulting in strong genetic differentiation among populations. By using molecular markers, scientists were able to find out that desert Drosophila is an exception to this typical pattern. Results showed that the molecular markers were very similar among populations even though the populations themselves were geographically distant from each other. They analyzed the behavior of the fly and realized that factors such as constant reproduction, longevity and flight capacity are key elements to prevent species fragmentation. By showing that populations not always follow what would be a predicted pattern in a specific environment, this study led to a deeper analysis of the behavior of populations and how this affects the genetics within a species.

Understanding population ecology goes along with understanding some of the principles that constantly affect population dynamics. For sure, the prime goal of a population is to grow and become fitter in the environment. We know that some species are ruled by the necessity of cooperation among populations (i.e. Bees, ants, elephants, grasslands, etc); others are in constant competition, fighting for a spot in the ecosystem, and trying to get a portion of the limited resources (i.e. water, nutrients, mates, etc). Ultimately, an ever changing population is always interacting with other organisms, and permanently trying to maintain its ecological balance. As more advanced technology becomes available, we are going to have a better understanding of such dynamics.

1. Derocher AE. 2005. Population ecology of polar bears at Svalbard, Norway. Popul Ecol 47(3):267-75.

2. Pfeiler E and Markow TA. 2001. Ecology and population genetics of Sonoran Desert Drosophila. Mol Ecol 10(7):1787-91.

Photos from Wikimedia Commons

Terrestrial Orchid Conservation

2010-02-04T09:44:00.000-08:00

contributed by Peter Zale

Based on worldwide evidence, scientists have declared that humankind is facing the sixth extinction event in the history of the planet, and that orchids are facing among the most severe of threats. Orchid conservation is a worldwide concern, but the leading research is performed in Australia, with a particular emphasis on species occurring in the Southwestern Australia floristic region (SWAFR), a global biodiversity hotspot. Biodiversity hotspots are areas boasting a proliferation of plant and animal species, and were estimated to once cover 12% of the globe, but current estimates are only 1-4%. Although this area contains comparatively few orchids when compared to tropical forests of northern South America, the SWAFR does harbor the highest number of terrestrial species of anywhere in the world. A departure from their epiphytic cousins (growing on the branches of trees or on rocks), terrestrial orchids (species that grow in the soil) represent special, but difficult cases of species conservation due to a complex blend of intrinsic and extrinsic factors.

Extrinsic factors are the reasons most frequently sited in the extinction of orchids. Upon European colonization, massive tracts of land in the SWAFR were converted to wheat plantations, destroying prime orchid habitat. Suppression of fire, competition from invasive species, increasing soil salinity, and climate change has also reduced orchid numbers. Despite the obvious effects of extrinsic factors, Current research indicates that extrinsic factors may play a secondary role to the intrinsic factors of terrestrial orchid conservation.

Of the intrinsic factors affecting orchid conservation, one of the most limiting factors is the relationship between orchids and mycorrhizae. Mycorrhizae are ubiquitously occurring fungi that form symbiotic relationships with the roots of many seed-bearing plants. Plants receive supplemental nitrogen, phosphorus, carbon assimilates, and water from fungi; all are necessary to support the growth of all plants. There remains debate concerning what fungi receive in return, but studies have shown that different forms of carbon move from the roots of plants to fungi. Some scientists have suggested that plants parasitize the fungi, receiving supplemental nutrients, but supplying nothing in return.

Terrestrial orchids have developed some of the most complex relationships of all. Species such as Rhizanthella gardneri do not produce green leaves and manufacture food through photosynthesis and are thus entirely dependant on a specific fungus from Melaleuca forests for nutrition. Another species, Microsteris media, can form a relationship with numerous fungal strains and is widespread throughout many different regions in Australia. This begs questions about the distribution and abundance of these fungi that seem to operate in unpredictable ways. Numerous studies have focused on the classification and cultivation of these fungi and strides have been made to clarify their relationship to orchids, but many evolutionary questions remain and culture of these organisms is constrained by inefficient methodology.

Were this not enough, the detailed beauty of orchid flowers owe their flamboyant forms and colors to a high degree of specialization resulting from relationships with often highly range restricted (endemic) pollinating insects. The Hammer orchids of the genus Drakaea consists of 9 species, all of which have a different species of Thynnine wasp as a pollinator. The recent extinction of Drakaea andrewsiae was preceded by the disappearance of its pollinating wasp, and it is likely that other species of Drakaea will follow because the already rare wasps are sensitive to the insecticides used on the wheat farms. This dependence on a particular pollinator follows a continuum of necessity through the orchid family, and the other end of this spectrum is dominated by plants that have the ability to self-pollinate and produce seed in the absence of a pollinator.

Intimate knowledge of intrinsic and extrinsic factors is necessary for orchid conservation, but knowledge of the role of orchid genes in maintaining orchid populations is also necessary. Genes provide conservation biologists with a species “blueprint” which can give clues about the evolutionary forces that act on species and how they impact population diversity and management strategies. Genetic variation can be measured at many levels, but the most robust information comes from patterns of variation in plant DNA. Patterns in DNA variation provide insight to the immediate effects of extrinsic and intrinsic effects and can help scientists identify priority populations and species of orchids.

In Australia, conservation of orchids occurs by managing existing orchid populations (in situ), assisted migration (moving) of orchid species to new sites, and the development of propagation methods for both orchid and mycorrhiza (ex situ). In situ conservation is considered to most efficient and preferred method of orchid species conservation. In situ conservation focuses on identifying existing orchid species populations that are particularly vulnerable to disappearance, and formulating conservation strategies that result in long term persistence of the population. Sometimes these populations face eminent danger due to land development and must be carefully moved to new sites that have been identified as potential orchid habitat. This practice of assisted migration has yet to catch on in many regions of the world, but has been successfully employed in the SWAFR. Ex situ conservation bridges the gap between In situ and assisted migration. Ex situ practices focus on isolating mycorrhizal fungi, cultivation of the fungi under laboratory conditions, and using it to germinate orchid seeds. Orchid seedlings and mycorrhizae are then used to supplement existing populations or introduced to new areas of suitable habitat.

An example is Rhizanthella gardneri. This species faces danger of extinction in the wild because soils in its habitat are subject to increasing salt content, and the extinction of the mammal responsible for spreading seeds of this species to new areas. Although assisted migration of this species failed, scientists were able to successfully propagate this species by replicating the conditions ex situ. Cultivation attempts require the successful culture of the Melaleuca tree, and the symbiotic fungus. Although many orchid species are considered impossible to grow in cultivated settings, success with Rhizanthella has provided a glimpse of hope to conserving other fastidious orchid species

(Melaleuca tree)

It is unlikely that all species of orchids will persist for the foreseeable future. Conservation efforts have focused on species with dwindling populations, but the question of long term conservation remains unclear for many species in the face of climate change. The fate of these species can only be clarified by long term studies that define the most important intrinsic and extrinsic factors governing the lives of each orchid species.

For additional information, check out this article:

Swarts N.D. and Dixon K.W. (2009) Terrestrial orchid conservation in the age of extinction. ANNALS OF BOTANY 104(3):543-556

Terrestrial orchids from around the world that are in culture at OSU (photos by Peter Zale):

Satyrium acuminatum - South Africa

Phragmipedium besseae - eastern slope of the Andes Mountains in Colombia, Ecuador, and Peru

Platanthera ciliaris from Lucas county, Ohio

Cypripedium parviflorum var. pubescens - Ohio, USA

Cypripedium kentuckiense - southeastern USA

Calopogon tuberosus - eastern USA

Geolocator technology aids in tracking Puffin movement during winter

2010-01-14T05:59:00.000-08:00

Puffins are found off the coast of Scotland and other areas of the North Sea. The populations disappear during the winter, but no one knew where they went or what they did whilst away.

A group of British researchers fitted Puffins with geolocator tags to track their movement over the winter. The results were very surprising. The birds go out into the middle of the Atlantic ocean. Researchers have yet to discover what they are eating or much about their behavior during the winter, except to know that they tuck their feet up into their feathers while sleeping. They know this because of the the tracking technology they used. Researchers wanted to know when the birds were in the air vs in the water and used tags on the feet for that determination. The only problem was that the tags on the feet dry out when feet are tucked into the feathers, and give a false reading while the birds are sleeping on the water.

To read more about the research, check out the report from BBC news: Puffins' winter odyssey. There's a video showing the tagging process - looks like fun!

Currents Collide and Coastal Waters Bloom near Patagonia

2010-01-12T10:57:00.000-08:00

This time of year is when ocean currents in the southern hemisphere come to life with phytoplankton. Satellite imaging gives a dynamic view of the algal bloom and the turnover that occurs when cold currents collide with warm ones.

See images and read all about it on today's posting for the Nasa Earth Observatory

Solving an ice age mystery

2010-01-12T08:34:00.001-08:00

"People who study the behavior of Earth's climate have been pondering a mystery of the last ice age. Why did the size of the Northern ice sheets fluctuate so dramatically, pushing global sea level up and down? "

Read more about this research on Discovery News.

Coral reefs - more than just a regular ol' hotspot

2010-01-12T07:57:00.000-08:00

Interesting article on the ultimate biodiversity hotspots:

Coral reefs are most fecund cradles of diversity - life - 08 January 2010 - New Scientist

In California, an Oak is an old pro at Cloning

2010-01-05T15:30:00.003-08:00

"In Southern California, a place where most everything is new, botanists have discovered something very old: a scrub oak that has been cloning itself for at least 13,000 years. . ."

Read the complete article in the New York Times.

White Lizards Evolve in New Mexico Dunes

2010-01-04T18:14:00.001-08:00

What happens in just 6,000 years since the formation of White Sands dune system in the American southwest? Adaptation to a white background environment by three species of dark-skinned lizards. Results from this study were published this week in the Proceedings of the National Academy of Sciences, authored by Rosenblum et al.

A summary of the paper is available from the New York Times observatory column.

I've always known that our local gravity is higher here than most other places in the USA

2010-01-03T17:22:00.000-08:00

Why else would my bathroom scale give me so many 'erroneous' readings?

The European GOCE satellite has been used to compile a map of Earth's gravitational field. Gravity varies across the globe, which may come as a big surprise to most people.

Read all about it: Europe's GOCE satellite probes Earth's gravity

Timely article

2010-01-02T07:00:00.000-08:00

Sustainability comes of age - from New York Times

"By HENRY FOUNTAIN"

"WHEN Andrew Pattison was looking to pursue a graduate degree in sustainability, he drew on his post-college experience working as a conservation biologist in upstate New York. Butterflies were his thing, and he produced numerous recommendations about what should be done to protect them. “I found that quote-unquote important people who were decision makers would read the reports I filed and then not follow them,” Mr. Pattison says."

"Those frustrations led him in a different direction. “I knew I wanted to study the way decisions were made on environmental policy,” he says. He also knew where many of the important decisions were made: in cities. With energy and climate policy, he says, “the problem is global, but all politics are local.”. . ."

Ancient DNA study links early European humans with modern day ones

2010-01-01T07:53:00.000-08:00

Svante Paabo and colleagues conducted a study on the remains of Paleolithic skeleton buried ca. 30,000 years ago. Using automated sequencing techniques and careful isolation of the ancient DNA, the team was able to place the mitochondrial DNA haplotype into the "U2" group. This haplotype is very rare in modern humans, but the presence of it in populations of today indicates a continuum of Paleolithic people with current European inhabitants.

Read all about the study: DNA analysed from early European (BBC news)

Mangroves, Dunes and Desert - Baja California

2009-12-31T19:37:00.000-08:00

[Click here to go to the Nasa Earth Observatory image and article]

"Along the west coast of Baja California, roughly one third of the peninsula’s length from its southern tip, the land pokes westward like a slightly bent elbow. The area is a combination of sparsely vegetated desert, sand dunes, mangroves, braided streams, shallow coastal waters, and mountainous islands."

"In this astronaut photograph, taken from a vantage point west of the peninsula, north is toward the upper left. . ."

North Sentinel Island, Adaman Sea

2009-12-30T15:40:00.000-08:00

[click link to go to article]

From Nasa Earth Observatory

"Five years ago this past December 26, a huge earthquake offshore of Sumatra, Indonesia, unzipped a 1,600-kilometer (994-mile) stretch of the sea floor, heaved it upward as much as 5 meters (16 feet), and unleashed devastating tsunamis that scoured coastlines of countries around the Bay of Bengal and the Andaman Sea. Hundreds of thousands of people died. . . "

This article describes the after effects of the 2004 tsunami and mentions the indigenous tribe inhabiting the island.

Animals, Plants Forced to Migrate to Keep Pace with Climate : Discovery News

2009-12-30T15:04:00.001-08:00

click here to read article

As climate changes, species will need to relocate to follow their ideal climate, generally by uphill or to higher latitudes. But how quickly will this change occur? . . .

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Storm 'Echoes' Could Break Up Ice Sheets : Discovery News

2009-12-30T14:58:00.001-08:00

click here to read article

Slow tsunami-like waves are rolling into the waters off Antarctica. Generated by storms churning as near as the Patagonia coast and as far away as the Gulf of Alaska, they jostle the continent's giant floating ice shelves.

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Mayon Simmers : Big Pics : Discovery News

2009-12-30T14:49:00.001-08:00

click here to read article

This Dec. 15 satellite image shows the volcano Mayon in the upper left and the town of Legazpi to the lower right. It doesn't take a volcanologist to see that there has been good reason to worry about the people living near the currently slowly erupting volcano. If the eruption becomes explosive, tens of thousands could be in danger. The past time Mayon really let loose, in 1814, it killed about 1,500 people.

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Welcome to the Current topics in Biogeography blog!

2009-12-30T12:14:00.000-08:00

I teach a graduate course in biogeography every other year at The Ohio State University (Department of Evolution, Ecology, and Organismal Biology). This blog will be a place to publish summaries of current biogeography articles, which will be written by my students as class assignments. My Winter Quarter 2010 class will be the first contributors to the blog.