Tyler Frankel, Biological Sciences
"Negative Frequency-Dependent Selection in Xiphophorous helleri"
Faculty Mentor: Dr. Tamra Mendelson
Expected Graduation Date: Spring 2011
One of the fundamental aspects of maintaining population heterogeneity is the retention of novel or rare phenotypes in the population. One of the ways in which populations can maintain such heterogeneity is through negative frequency-dependent selection. Based on this mode of selection, females would be expected to seek out and mate with males that exhibit rare phenotypes (i.e, traits having low genetic frequency), thereby ensuring that those phenotypes remain viable within the population and, thus, maintain genetic variation for that characteristic. Indeed, negative frequency-dependent selection has been the focus of studies utilizing natural and artificial populations. The present research project is designed to investigate the validity of negative frequency-dependent selection of novel traits in the freshwater swordtail Xiphophorous helleri (Poeciliidae). This species is ideally suited to this study since it exhibits several distinct color morphs and utilizes an ovoviviparous reproduction strategy, which will allow for observation of courting behavior (mate selection) prior to copulation. Using green, black and brick color variations, I will attempt to verify whether X. helleri females will preferentially select phenotypically novel males from an otherwise homogenic population of males exhibiting the female's color phenotype.