Dissertation research: To see or not to see or to see again: regressive evolution and Dollo's Law in North American cavefishes (Pisces: Amblyopsidae)

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The hypothesis that evolution is truly irreversible, known as Dollo's Law, has become a question of increasing interest, as several recent studies have made claims that complex structures, such as an eye or insect wing, can be recovered after loss. For example, recent analysis of a family of cavefishes from the southeastern U.S. suggests that a surface-dwelling fish with functional eyes has evolved from a blind, cave-dwelling ancestor. The alternative is that an ancestor with functional eyes repeatedly gave rise to separate blind cavefish species. To test these hypotheses, this study examines genes involved in eye development. The alternative hypotheses make distinct predictions about similarities and differences between species with regard to molecular changes in eye-related genes in blind versus sighted lineages. However, the differences may be subtle and examining a multiple-gene dataset will provide the power needed to test the predictions of Dollo's Law versus reverse evolution. This study demonstrates a way forward when other analyses suggest, but cannot confirm, that reevolution of complex structures is likely.This study will provide insight into the molecular evolution of several eye- and pigment-related genes in a vertebrate and might aid understanding of visual dysfunctions in humans. In addition, discoveries from this research will be incorporated into ongoing education and outreach efforts to local schools and organizations. Educational activities will confront common misconceptions about "use and disuse" in evolution, and promote understanding of how genes and environments jointly affect traits.