Title

POPULATION-LEVEL VARIATION IN A PHEROMONE COMPLEX ACROSS SPECIES' GEOGRAPHIC RANGE

Date of Award

Winter 2016

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Dr. Carl Anthony

Abstract

Protein pheromones in salamanders of the genus Plethodon have experienced rapid and pervasive directional selection. Variation in mate recognition components, such as the sex-specific pheromones used by plethodontid salamanders, may play a role in sexual incompatibility and therefore provide a biochemical mechanism for the maintenance of discrete, isolated populations. Recent studies suggest that multiple, genetically distinct lineages of Plethodon cinereus are present throughout their broad range. Two of these lineages, referred to here as the Ohio (OH) and Pennsylvania (PA) clades, are represented in northern Ohio, spanning the state along the southern shore of Lake Erie. This distribution pattern creates a unique opportunity to study how phenotypic differences may reinforce population boundaries and possibly lead to speciation. The objectives of present study were to (1) characterize the pheromone profiles of male P. cinereus, (2) determine pheromone variation among populations and between the two distinct lineages present in Ohio, and (3) determine if males show more interest in the scent of females in their own clade compared to those from a different clade. The composition of proteins associated with two known courtship pheromones (Plethodontid Modulating Factor (PMF) and Plethodontid Receptivity Factor (PRF)) were compared among 8 populations in northern Ohio. Analyses of Similarity (ANOSIM) suggest that both PMF and PRF profiles differ among populations but not between clades. To test the ability of animals in each lineage to recognize potential mates, males from a single lineage were exposed to the scent of females from within and outside of that lineage. In my comparisons, males showed no difference in preference for female scent between trials. These data suggest that the sex-specific pheromones of P. cinereus in the OH and PA clades in northern Ohio are not yet different enough to play a role in reproductive isolation leading to speciation between the two genetic lineages. To understand the maintenance of isolated populations in this system, data on specific pheromone isoforms and the effect of those pheromones on mate compatibility should be the focus of future studies.

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