Subterranean Fishes of the World

5630

2022

AIM 2022

36

Extreme environments with their well-defined and replicated selective regimes provide powerful natural experiments that allow us to explore the extent to which evolution is repeatable and predictable. For example, livebearing fishes of the family Poeciliidae that span over 40 million years of evolutionary divergence have colonized caves and springs with high concentrations of toxic hydrogen sulfide (H2S). Our research has documented clear signatures of convergent evolution across levels of organismal organization, highlighting the repeatability of evolutionary processes. However, our work has equally found evidence for lineage-specific evolutionary changes, giving rise to substantial variation in the degree of convergent evolution among sulfide spring lineages. A major question is whether apparently idiosyncratic, lineage-specific evolutionary changes are reflective of chance events inherent to evolutionary processes, or whether they are also influenced by deterministic genetic or ecological factors. I will present some new research indicating that variation in the degree of convergence is not merely noise associated with evolutionary contingency. Rather, cryptic ecological variation that is frequently ignored when we employ reductionist approaches contributes significantly to adaptive evolution and shapes the degree of convergence among lineages. In addition, I will show that evolutionary repeatability has its limits and frequently breaks down at the genomic level, even among lineages that exhibit high levels of convergence in phenotypic traits. Overall, I will argue that addressing some of the most pressing questions in evolution will require us to embrace the complexity of the environments and the organisms we study and to explicitly integrate evolutionary analyses across organizational and phylogenetic scales.

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