Meeting Abstract
Evolutionary theory predicts that natural selection acts to maximize fitness by optimizing a life history that includes trade-offs between reproduction and survival. While there is compelling evidence that selection acts in this way, we know remarkably little about the physiological and molecular mechanisms that generate and regulate these trade-offs. With more than 20 years of ecological, behavioral, and genetic data, the least killifish is an excellent model to examine the endocrine and molecular systems that mold the trade-offs we observe. Multigenerational exposure to either high conspecific density or high predation in natural populations has selected for divergent life history traits of this live-bearing fish: females from populations at historically high densities consistently are smaller in size with small clutches of large offspring, while females from low-density populations with high predation risk are larger in size, with large clutches of small offspring. We are testing the hypothesis that selection has integrated alternate physiological regulatory networks that coordinate the expression of these life history traits according to perceived changes in the environment. Our initial studies support this idea, as phenotypic and endocrine responsiveness to environmental conditions and interactions between neuroendocrine axes vary between populations that were historically exposed to either high-density or high predation risk. Future studies that combine selection experiments with functional genomic, epigenetic and endocrine analyses will resolve the complex but efficient connections within physiological and molecular networks that generate specific phenotypic trade-offs that maximize fitness in populations under different selection pressures.
