Exploring the use of genetic markers to assess the effects of contaminant exposure in free-living red swamp crayfish, Procambarus clarkii

The goal of this project was to examine how environmental stressors, in this case, contaminant exposure, affect natural populations over the long term. Genetic effects were proposed by many authors in the last three decades but work to explore these has been varied widely in its approach to study design, sampling, and ability to test the relevant hypotheses. This project was designed to fit an evolutionary and population genetic framework for using genetic tools to assess the effects of environmental stressors in natural populations. This framework included careful consideration of various evolutionary and population genetic models that could result in genetic patterns observed in wild populations. I present here an extensive review of the empirical efforts made to date to test for genetic change in response to contaminant exposure in field situations. I concluded that while several very well-designed studies have shown strong correlations between chronic contaminant exposure and genetic patterns, many others have drawn strong conclusions from incomplete evidence. I suggest that the consistent addition of exposure documentation, thorough sampling including replicated contaminated and reference sample populations, and careful consideration of alternative hypotheses when reviewing results would strengthen studies of this type, in addition to important new statistical and genetic tools. The second paper here documented the development of 23 microsatellite markers for red swamp crayfish and their potential utility in population surveys. The third presented the results of the genetic analysis of the field test, placed in the context of evolutionary and population genetic models for change, and the review paper. Genetic patterns did not unilaterally support any one of the proposed hypotheses of genetic change, bottlenecking, selection, or mutation. However, as a whole, evidence supports a selection hypotheses. These data provide direction for further study of selection in red swamp crayfish which may be correlated with contaminant exposure. These papers will hopefully provide a solid background against which future work may be done on contaminant effects in wild populations, and using genetic patterns to study environmental stress in general.