Sue Bertram, Ph.D.
Full Professor
Undergraduate Chair
Department of Biology
Carleton University
1125 Colonel By Drive
Ottawa, Ontario
Canada, K1S 5B6
Office: CTTC 4631
Lab: CTTC 4440G
Email: sue.bertram@carleton.ca
Twitter: @sue_bertram
Blog: labchirps.wordpress.com

Research: Maintenance of Variation in Sexually Selected Traits

How genetic variation is maintained in traits that enhance fitness remains a fundamental dilemma in evolutionary biology. Theoretically, fitness-conferring traits should have minimal genetic variation because heritable traits that increase fitness should proliferate until they become fixed in a population. Traits that enhance mating success should strongly influence fitness and therefore display minimal amounts of heritable variation. However, sexually selected traits tend to exhibit even higher levels of heritable variation than other fitness-enhancing traits. Our research addresses how genetic and environmental variation is maintained in sexually selected traits, and focuses on the field cricket as the model organism. We use an animal behaviour approach that incorporates tools from nutritional ecology, ecological physiology, and quantitative genetics. Our laboratory-based empirical research quantifies the phenotypic and genetically based variation in condition, life-history traits, and sexually selected traits and determines how this variation is influenced by diet and physiology.

We are presently (1) estimating the structure of sexual traits and female preference functions to understand how traits are likely to experience selection; (2) quantifying how diet affects sexual traits to determine their condition-dependent nature; and (3) assessing how diet influences the physiological foundations of sexual trait variation. Together this work will determine the multivariate structure of the sexual traits, their condition-dependent nature, their physiological and genetic underpinnings, whether females receive indirect benefits, and the potential for frequency-dependent fitness. Overall, our research will explicitly test two theories for the maintenance of high genetic variance – genic capture and frequency-dependent fitness. Long-term, the overarching goal of our research program is to contribute to a more complete understanding of how high genetic variance is maintained in traits that enhance fitness.

Male crickets signal acoustically to attract mates. They exhibit extensive variation in how much, how often, how loud, and how sexy they call. My research team explores calling behaviour of crickets in an attempt to understand the environmental and genetic underpinnings of this variation. A signalling male cricket is pictured here.