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Research Interests
My research focuses on the evolution of secondary sex traits. I am interested in (1) the coevolution of ornaments and preferences, (2) the evolution of genetic architecture of these traits, and (3) the relative importance of each of the mechanisms of preference evolution (e.g. Fisherian mechanism, condition-dependent indicator mechanism, sensory bias, etc.) in driving the evolution of secondary sex traits. My dissertation research is partitioned into a theoretical component and an empirical component.
To address the theoretical aspects of my interests I am building a quantitative genetic model to evaluate the relative importance of each of the preference-evolution mechanisms in the evolution of secondary sex traits. Monte Carlo simulations are extremely powerful tools in relaxing many of the assumptions ingrained in mathematical models. Specifically, the entire genetic system is explicitly modeled in a finite population. The first model will include one ornament and one preference, with later models adding more ornaments and preferences. The idea is to see if genetic correlations can evolve, a requisite of all of the models of mate choice evolution. If the necessary genetic correlations do evolve, how much of the variance in mating success is due to genetic covariance between genes responsible for ornaments and preferences or between genes responsible for preference and viability? Partitioning the variance in this way will draw a distinction between the Fisherian mechanism and indicator mechanisms of preference evolution.
On the empirical front, I will evaluate the genetic architecture of two ornaments (song and cuticular hydrocarbon (CHC) profile) and preferences for these ornaments in wild Drosophila melanogaster. Using inbred lines derived from a local wild population, I will perform diallel crosses and measure both song characteristics and CHC profiles, as well as preference functions for each genotype. The advantage to this approach is that I will be able to make independent repeated measures on the same genotype to determine trait values. Similarly, this approach yields information on the relative maternal and paternal contribution (i.e., combining ability) of each genotype, thus elucidating the inheritance pattern of the traits. Understanding the genetic architecture of multiple ornaments and preferences will provide the necessary range of parameter values to be used in the model outlined above.
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Current Projects
1. Building simulation model described above.
2. Parentage analysis on two populations of the Northern pipefish, Syngnathus fuscus, from Virginia and New Hampshire.
3. Replication of Bateman's (1948) experiment on the cause of sexual selection in Drosophila melanogaster. While Bateman's study has impacted the field of sexual selection tremendously, some criticisms of his experimental practices have raised questions as to the validity of the conclusions drawn from his results. Clay Small and I are replicating the experiment in a way that addresses many of the potential pitfalls in Bateman's experimental design.
4. Chemical signaling in Syngnathus scovelli, the Gulf pipefish. Over 20 years of research has been conducted on mate choice in pipefishes, but investigations have been limited to visual cues. Given the ubiquity of chemical communication in animals, I tested for (1) sex-recognition, (2) size-discrimination, and (3) social context. I found that males, but not females, prefer the scent of the opposite-sex over the same sex or control. However, males do not show a preference for female size, a sexually selected trait. Moreover, males do not discriminate between the scents of a female who was exposed to a male, female, or an empty tank. These results show that male pipefish have the ability to use chemicals in sex-recognition, and these cues may play an important role in courtship, though the exact function remains to be identified.
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