Mating evolution in Gambusia (Poeciliidae) : an integration of behavior, molecules and morphology



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Female mate choice and male courtship display are critical behaviors for the understanding of character evolution driven by sexual selection. This thesis is designated to understand the evolutionary mechanism of these two behaviors with mosquito fish (Gambusia). In the first chapter, collaborated with Dr. Mark Kirkpatrick, we demonstrated positive coevolution of courtship display and morphological signatures of male coercion and male advantage in sexually antagonistic adaptation across 10 Gambusia species. This finding suggested that male display may have caused the evolution of morphologies involved in SAC, or conversely it may have evolved as a palliative byproduct of the morphologies. This unexpected observation raised new interpretation about evolutionary cause and consequence of displays across different mating systems. The second chapter examined whether neuromolecular underpinning of G. affinis female mate choice is canalized or plastic in mating systems that show variable extant of mate choice. With Dr. Mary Ramsey, we should positive correlations between gene expression and female preference strength during exposure to courting heterospecific males, but a reversed pattern following exposure to coercive heterospecific males. This suggested that the neuromolecular entities associated with female preference are plastic and responsive to different male phenotypes (courting or coercive) rather than a canalized response linked to mating system. Further, I proposed that female behavioral plasticity may involve learning because female association patterns shifted with experience/age. Compared to younger females, I find that more experienced females spend less time near coercive males but associate more with males in the presence of courters. We thus suggested a conserved learning-based neuromolecular process underlying the diversity of female mate preference across the mate choice and coercion-driven mating systems.