August 20, 2020
Tobler to present Division of Biology Seminar
Michi Tobler, associate professor in the Division of Biology, will present "Replaying the Tape of Life: How Selection in Extreme Environments Leads to Predictable Evolutionary Outcomes" as part of the Division of Biology Seminar Series at 3:30 p.m. Monday, Aug. 24. This seminar will be delivered via Zoom.
Stephen J. Gould made a strong case for the importance of contingency in evolution, famously quipping that replaying the "tape of life" would lead to different outcomes every time. Today, we can conduct Gould's impossible experiment by integrating evolutionary analyses across organizational and phylogenetic scales to explore under what circumstances evolution is actually predictable. Freshwater springs discharging water rich in toxic hydrogen sulfide, or H2S, are extreme environments that provide the consistent selective regimes required for such endeavors. Among the few organisms that can persist in these springs are livebearing fishes of the family Poeciliidae. Studying the mechanisms underlying adaptations to sulfide springs across different lineages, we have shown that tolerance to H2S is mediated by the convergent modification of highly conserved physiological pathways associated with essential mitochondrial processes. The same pathways, genes, and — in some instances — codons are implicated in H2S adaptation across lineages that span 40 million years of evolution. In addition, adaptation to the extreme environments has consistently resulted in the emergence of reproductive isolation between populations, causing the emergence of new species. Overall, these results suggest that replaying the tape of life in extreme environments did actually lead to similar outcomes every time.