Extreme environments impose strong selective pressures on phenotypes and provide a context within which to explore specific questions about differentiation and adaptation. Multiple species and populations of Poeciliids have independently colonized multiple springs with toxic concentrations of hydrogen sulfide (H2S). The sulfide spring fish our group studies provide a unique opportunity for an integrative approach to studying adaptation because: 1. the environmental gradients, whether streams are sulfidic or non-sulfidic, are clearly defined and replicated, 2. the environmental gradients have known biochemical consequences for fish so we can better understand the kinds of biochemical pathways where adaptation is likely to have occurred, and 3. the divergence between populations is recent, making it easier to separate differences between populations that result from adaptation from differences driven by other evolutionary processes. 

Together with Dr. Michi Tobler at University of Missouri – St. Louis, we are studying multiple sulfide spring populations and related non-sulfidic populations in the family Poeciliidae to understand parallel adaptation, adaptive trait divergence, differentiation in gene sequences, and gene expression patterns. We are taking a multi-omics approach to determine the relative contributions of different regulatory processes to the convergent phenotypes we observe in the sulfidic species. This involves the collection of analysis of multiple types of data including physiological trait measurements, DNA sequencing data across species and populations to determine genomic variation, and RNA sequencing to better understand variation in gene expression patterns. Our research has broad implications for better understanding how organisms across the tree of life have adapted to different environments and the potential for contemporary populations of different species to continue to adapt to changing ecosystems, particularly in the face of anthropogenically induced environmental change.