Meeting Abstract

5.2  Jan. 4  Moving away from the mean: does trophic divergence in sympatric populations of the Gold-breast Splitfin, (Ilyodon furcidens) increase fitness? HUIZINGA, M.*; GHALAMBOR, C.K.; Colorado State University Meribeth.Huizinga@colostate.edu

A central focus of evolutionary ecology is to understand how historic and current processes interact to generate and maintain patterns of diversity within and between species. Examining the role of natural selection in driving local adaptation and population divergence provides a framework from which to understand the processes that constrain adaptive evolution. Both theoretical and empirical work are recognizing that natural selection can lead to adaptive divergence within populations (i.e. in sympatry) and that individual specialization, speciation events, and whole adaptive radiations may commonly occur in sympatry. For example, the use of the mouth for pacifying and handling prey items has resulted in a variety of resource polymorphisms among vertebrates, altering morphology, life history traits and behavior. While several studies have demonstrated the presence of coexisting ecological morphs, few have established a link between this intraspecific morphological variation and fitness. I compared geographically isolated populations of the livebearing fish, Ilyodon furcidens and described the morphological differences within and between the sample populations. I found that I. furcidens exhibits morphological variation in a suite of trophic characteristics, and that populations show either a unimodal or bimodal frequency distribution of relative mouth width. Morphological variation was related to fitness estimates, and are discussed in the context of maintenance of morphological variation through selection, with implications for disruptive and frequency dependent selection.