Garnett, Jacqueline – A Comparative Phylogenetic Analysis of Accessory Gland Evolution in Fishes (Dr. Sigal Balshine)

Sperm competition arises when two or more males compete to fertilize a female’s eggs; this phenomenon puts an evolutionary pressure on males to develop adaptations that will increase their reproductive success. It is thought that one such adaptation is the development of accessory glands, which are secondary sexual organs that assist in sperm production and storage. Accessory glands can be found across a wide variety of taxa, but their phylogenetic origin is largely unknown. Within fishes, only a relatively small number of species have accessory glands. I employed a discrete comparative phylogenetic analysis to analyze the evolutionary history of accessory glands in teleost fish species (Teleostei), based on a previously published phylogeny for fishes by Rabosky et al. (2013). The presence or absence of accessory glands was identified in 107 families; this information was compared to their evolutionary histories to determine the number of times that accessory glands independently evolved across the studied lineages. Future studies may expand upon these results to elucidate the phylogenetic relationship between accessory glands, mating systems, and the presence of alternative reproductive tactics. Furthermore, the predicted relationship between sperm competition and the evolution of accessory glands can then be explicitly tested. This work will shed light on the types of selective forces that lead to the evolution of accessory glands and help to create a more complete understanding of how fish and other vertebrates respond to selective pressures on their reproductive success.