Evolutionary response to stressors

SREL Collaborators: Everyone in the Lance lab

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The global decline of amphibian populations has been linked to many stressors including climate change, disease, and contaminants. What is clear is that not all populations respond the same way. In typical ecotoxicology studies it is common to use one species (and often Xenopus which is unlike any other anuran) and extrapolate out to predict how a contaminant is going to affect amphibians. Often eggs from several clutches are mixed together to "homogenize" the genetic variation. I understand this approach from a straigt toxicology perspective but as an evolutionary biologist I am much more interested in the variation! It's the variation in response to stressors that may impact which populations persist and which go extinct. Our lab's primary interest in ecotoxicology relates to understanding how populations may respond to different and multiple stressors. As a first step to try and get at this we examined multiple species, multiple populations, and multiple clutches within each population. Not surprisingly, when we looked at the response to cFlamingoBay1opper stress we have found significant variation at each level. Now we are taking a multi pronged approach to determine the sources of variation. For example, Wes is using a combination of quantitative genetics and genomics to measure heritability of several phenotypes and to identify candidate loci. We've been working with Ken Jones on some gene expression studies and are working with Ben Parrott and John Bowden to examine epigenetic effects. We are fortunate to have populations of amphibians on the SRS that have been exposed to metal stressors for different lengths of time (from 6 to 35 years) which may allow us to compare short and long-term population responses to stress. In the site with a 35 year history to coal fly ash contamination there is evidence of adaptation. In our main study site with more a more recent history of contamination there is no evidence of adaptation, but there is ample variation and Wes' work suggests a large portion is additive genetic variation. In reality all populations are likely to be exposed to multiple stressors which can certainly complicate the evoltuionary response.

Thus, we are also initiating studies looking at the interacitve effects of exposure to multiple stressors including: metal mixtures, low dose radiation, altered hydroperiods, and disease. For example, in the spring of 2013 we conducted a large mesocosm study with 3 levels of copper and 2 hydroperiod lengths. Often we see that copper exposure delays developement so what will happen when exposed to copper and a short hydroperiod? So far we have seen that southern toads were able to metamorphose from the "high copper, short hydroperiod" treatment but they were small, physiologically less fit (in hopping trials), grew more slowly, and had very low survival for the first month after metamorphosis.

This avenue of research will likely play a major role in the future of the Lance lab and prospective students interested in this area are encouraged to contact Stacey.

The content and opinions expressed on this web page do not necessarily reflect the views of nor are they endorsed by the University of Georgia or the University System of Georgia. Jason O'Bryhim & Stacey Lance 2013