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Invasion Ecology at ESA 2016

A guest post from PLOS Ecology Reporting Fellow, Kelsey K Graham, on research from the Ecological Society of America Scientific Meeting in Ft. Lauderdale, Florida, August 7-11, 2016.


Ft. Lauderdale, Florida seemed a fitting place for ESA 2016, particularly given this year’s theme – Novel Ecosystems in the Anthropocene. Florida is an invasion hotspot – the state has over 500 exotic fish and wildlife, and more exotic amphibians and reptiles than anywhere else in the world. This is largely due to Florida’s tropical climate and the continuous influx of exotic species that are brought both intentionally and unintentionally. The United States is the world’s largest importer of exotic animals, mostly used in the pet trade, and Florida is a significant participant in this. Large cities like Ft. Lauderdale also act as hubs for unintentional exotic species introduction. As ESA conference goers looked out over the Ft. Lauderdale port, it was easy to be reminded of the many ways that exotic species came to Florida – as hitchhikers on planes, boats, automobiles and other common vehicles of human movement.

Port Everglades, Ft. Lauderdale, FL (Photo credit: Bruce Harlick)
Port Everglades, Ft. Lauderdale, FL (Photo credit: Bruce Harlick)

Invasive species are bringing with them huge costs, both ecological and economical. Invasive species are considered the second greatest threat to biodiversity, just behind habitat loss (Wilcove et al., 1998). This decline in biodiversity is largely attributable to invasive species preying on native species or competing with them for limited resources. Additionally, it is estimated that the United States spends $120 billion dollars per year in damages due to invasive species (Pimentel et al., 2005).

Successful invasions follow a similar trajectory – a species is introduced, it establishes, and then it spreads. Truly invasive (pest) species will also cause harm to native species or hinder ecosystem services. A recent study published in PNAS (Walsh et al., 2016) found that one ecosystem service, water clarity, was degraded by the invasion of the spiny water flea. Researchers estimated the cost of restoring this service would be between US$85.5-US$163 million. But not all exotic species successfully establish in their new range, and many more don’t cause significant damage. This leaves ecologists with the daunting task of assessing the risk of newly invading species. Even when there is sufficient evidence that a species is a problem, ecologists and managers are then left with the likely more daunting task of successfully eradicating and/or controlling that species.

The field of invasion ecology has advanced in leaps and bounds since its inception in 1958 with Elton’s publication of The Ecology of Invasions by Animals and Plants. Researchers are continually implementing innovative approaches to assessing and controlling invasive species. But there are still many gaps in our knowledge, and the final ESA 2016 invasion ecology symposium titled “The Future of Invasion Ecology” highlighted some of the major considerations facing the field today.

One of the major themes from the symposium was that invasion ecology is a subset of community ecology. No species exists in a vacuum, so we must view invasions from the community perspective. A great example of that came from Michael B. Mahon, a graduate student at Miami University. His work showed a strong correlation between white-tailed deer abundance and an increase in invasive earthworms, which negatively affect the nutrient cycles of invaded soils.


Northern forests in North America have no native earthworms, but species have recently migrated north or were introduced from Asia and Europe. (Photo credit: schizoform)
Northern forests in North America have no native earthworms, but species have recently migrated north or were introduced from Asia and Europe. (Photo credit: schizoform)

Another theme was that invasion ecologists tend to be in constant search for generalities among invasive species. This leads to an almost endless list of emerging hypotheses on what makes a species invasive. But speakers cautioned that searching for widespread generalities may not always be helpful. There will always be exceptions to the rule, and from a management perspective, managers need specific tools to apply to their system and the specifics of the invasion situation at hand. Therefore, studies that focus on a specific system can often yield the best management solutions.

Symposium speakers also encouraged more biogeographic studies. By contrasting community structure in invaded and native ranges, we may gain insight into why species are held in check within their native range, but become pervasive within their invaded one.


Kudzu (an invasive plant introduced from Asia) has completely enveloped a barn in Tennessee. (Photo credit: Steve)
Kudzu (an invasive plant introduced from Asia) has completely enveloped a barn in Tennessee. (Photo credit: Steve)

Carla D’Antonio (UC Santa Barbara) concluded the conference stressing the importance of long term studies. She encouraged young researchers in invasion ecology to set up study plots now that they can follow throughout their career. Most studies only last a few years (at best), which means we are only capturing a short snapshot within the history of a constantly adapting ecosystem. An exotic species may be pervasive now, but its persistence may be short lived. If we are lucky, abiotic and/or biotic factors may eventually control the exotic species. We need long term studies to understand what factors lead to invasive species persistence so we can focus our efforts on understanding and controlling the most damaging invaders.

For more information on invasive species and current research in invasion ecology, check out the research websites of symposium speakers:

Dr. Wayne Dawson – Durham University

Dr. Erik Aschehoug – Louisiana State University

Dr. Ingrid Parker – University of California, Santa Cruz

Dr. Brian Leung – McGill University

Dr. Saara J. DeWalt – Clemson University

Dr. Carla D’Antonio – University of California, Santa Barbara


Kelsey Graham is a Ph.D. Candidate at Tufts University, Department of Biology. Her research interests lie at the intersection of invasion ecology and animal behavior, with a focus on interspecific interactions between native and non-native species. Kelsey uses an interdisciplinary approach to answer questions from multiple theoretical perspectives, providing a comprehensive assessment of an invasive species within their invaded ecosystems. Her current focus is on an invasive bee, the European wool-carder bee (Anthidium manicatum), and its impact on native pollinators and plants. Kelsey has authored papers in peer reviewed journals, as well as general audience publications.  (Follow Kelsey on Twitter @woolcarderbee)



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