PhD Student UMASS Amherst Holyoke, Massachusetts, United States
Abstract Body : Stereotypical tradeoffs exist between traits in cave-adapted Astyanax mexicanus, the native habitat of which is quite extreme. Cave morphs must survive and reproduce in underground caves with conditions including, but not limited to, low dissolved oxygen content, seasonal prey availability, and lack of light. Within cave morph evolution, the reduction of certain traits alongside the expansion of others characterizes a trend suggesting tradeoffs influence the direction of evolution. In particular, key cave adaptations are associated with expanded or reduced traits derived from Neural Crest Cells (NCC). Expanded NCC-derived traits include tooth number and bone density, whereas reduced phenotypes include muscle mass and pigmentation. We use an F2 hybrid population between surface and cave fish to assess potential developmental tradeoffs in NCC-derived traits. Negative correlations would imply a tradeoff between one trait and another, such that selection for an expansion in one trait would result in the reduction of another. If true, this could explain, at least in part, the rapid and stereotypical changes that are observed across cave-adapted A. mexicanus populations, as well as in other troglodytic species. Alternatively, traits may be evolving independently but in parallel owing to a common axis of selection. In any circumstance, this study provides insights into the mechanisms of trait tradeoffs and the basis of convergent/parallel evolution.
