Genetic basis for rapidly evolved tolerance in the wild: adaptation to toxic pollutants by an estuarine fish species
Citation:
Nacci, D., D. Proestou, D. Champlin, J. Martinson, AND E. Waits. Genetic basis for rapidly evolved tolerance in the wild: adaptation to toxic pollutants by an estuarine fish species. MOLECULAR ECOLOGY. Blackwell Publishing, Malden, MA, 25(21):5467–5482, (2016).
Impact/Purpose:
This manuscript describes experimental studies that contribute to our understanding of the ecological risks associated with chronic contaminant exposures to wildlife populations. Here, we assessed genetic patterns associated with long-term response to an important class of highly toxic environmental pollutants. Specifically, chemical-specific tolerance has rapidly and repeatedly evolved in an estuarine fish species resident to estuaries of the Atlantic U.S. coast. We used laboratory studies to characterize variation among laboratory-reared progeny of fish from populations known to vary in their sensitivity to these pollutants to infer mechanisms of toxicity and tolerance. Results of these studies demonstrate the value of molecular tools to diagnose and predict effects of chemical stressors and characterize the mechanisms and costs of toxic and compensatory responses to chemical stressors by wild populations. General impacts from this contribution include improved understanding by managers and scientists of links between human activities, natural dynamics, ecological stressors and ecosystem condition.
Description:
Atlantic killifish (Fundulus heteroclitus) residing in some urban and industrialized estuaries of the US eastern seaboard demonstrate recently evolved and extreme tolerance to toxic aryl hydrocarbon pollutants, characterized as dioxin-like compounds (DLCs). Here we provide an unusually comprehensive accounting (69%) through Quantitative Trait Locus (QTL) analysis of the genetic basis for DLC tolerance in killifish inhabiting an urban estuary contaminated with PCB congeners, the most toxic of which are DLCs. Consistent with mechanistic knowledge of DLC toxicity in fish and other vertebrates, the Aryl Hydrocarbon Receptor (ahr2) region accounts for 17% of trait variation; however, QTLs on independent linkage groups and their interactions have even greater explanatory power (44%). QTLs interpreted within the context of recently available Fundulus genomic resources and shared synteny among fish species suggest adaptation via inter-acting components of a complex stress response network. Some QTLs were also enriched in other killifish populations characterized as DLC tolerant and residing in distant urban estuaries contaminated with unique mixtures of pollutants. Together, our results suggest that DLC tolerance in killifish represents an emerging example of parallel contemporary evolution that has been driven by intense human-mediated selection on natural populations.
