Genomic changes underlying adaptation to sulfidic environments

Poecilia mexicana and P. sulphuraria have independently colonized multiple springs with toxic concentrations of hydrogen sulfide (H2S). Such extreme environments impose strong selective pressures on phenotypes and provide a context within which to explore specific questions about differentiation and adaptation. The sulfide spring fish provide a unique opportunity for an integrative approach to studying adaptation because:

1. the environmental gradients are clearly defined and replicated,
2. the environmental gradients are physiologically explicit, with known biochemical consequences; and
3. the divergence between populations is recent.

Together with Dr. Michi Tobler at Kansas State University, we are using sulfide spring populations of Poecilia in three different river drainages to study adaptive trait divergence, differentiation in gene sequences, and gene expression patterns. We are using RNA-sequencing of the transcriptomes of multiple Poecilia fish from several replicated sulfidic and non-sulfidic habitats to understand the mechanisms allowing survival in hydrogen sulfide rich waters. These genes are likely involved in adaptive trait divergence and reproductive isolation among ecotypes. In addition to differentially expressed genes, genes of interest are also identified by the presence of an excess of non-synonymous mutations between ecotypes. We are testing results in common-garden experiments in the lab.

• Kelley, J.L., Passow, C.N., Arias Rodriguez, L., Patacsil Martin, D., Yee, M.C., Bustamante, C.D., Tobler, M. (2016) Mechanisms underlying adaptation to life in hydrogen sulfide rich environments. Molecular Biology and Evolution. Accepted.
• Tobler, M., Henpitaa, C.R., Bassett, B, Kelley, J.L., Shaw, J.H. (2014) H2S exposure elicits differential expression of candidate genes in fish adapted to sulfidic and non-sulfidic environments. Comparative Biochemistry and Physiology Part A. 175:7-14. doi: 10.1016/j.cbpa.2014.04.012. [Online 5/2014]
• Pfenninger, M., Lerp, H., Passow, C., Kelley, J.L., Tobler, M., Funke, E., Greshake, B., Erkoc, U.K., Berberich, T., and M. Plath. (2014) Parallel evolution of cox-genes in H2S -tolerant fish: a key adaptation facilitates repeated niche shifts. Nature Communications.5:3873. doi:10.1038/ncomms4873. [Online 5/2014]
• Kelley, J.L., Passow, C., Plath, M., Rodrigues, L.A., Yee, M.C., and M. Tobler. (2012) Genomic resources for a model in adaptation and speciation research: characterization of the Poecilia mexicana transcriptome. BMC Genomics. 13:652. [link]. Highly accessed