Meeting Abstract
Extreme environments push organisms to their physiological limits, and recent literature is rich in studies investigating the mechanisms of adaptation that allow organisms to thrive in these habitats. However, little is known about why only some species are capable of initially colonizing these extreme conditions. A potential explanation for this phenomenon is exaptation, where the function of a trait with a particular function is co-opted for a new function given new conditions. Here we tested whether exaptation may have facilitated the colonization of H2S-rich habitats. H2S is lethal to most organisms, and streams rich in H2S are characterized by low biodiversity due to limited physiological tolerance. In contrast, the ancestral freshwater environments are rich in biodiversity. In Mexico, no physical barriers prevent movement between H2S-rich and freshwater springs. Interestingly, only some species of fish that inhabit ancestral freshwater habitats have successfully colonized H2S-rich springs, and the mechanisms that facilitate these events are unknown. We used a comparative approach to investigate the transcriptional responses upon H2S exposure in ancestral populations of species with a derived sulfidic population and species that lack an H2S-tolerant phenotype. We predict that ancestral populations of successful invaders will possess a higher H2S tolerance and plastically modulate gene expression upon exposure to H2S in a way that resembles gene expression patterns in derived H2S-adapted species. In contrast, species that have not successfully colonized sulfide springs are predicted to have lower H2S tolerance and mal-adapted gene expression responses. We are investigating the gene expression response of H2S exposure to elucidate possible exaptations that exist in species with derived sulfidic populations
