Investigating the female mate preference brain : identifying molecular mechanisms underlying variation in mate preference in specific regions of a swordtail (Xiphophorus nigrensis) brain

Choosing with whom to mate is one of the most important decisions a female makes in her lifetime and inter-individual variation of these preferences can have important evolutionary consequences. In order to get a complete understanding of why and how females choose a mate, we must identify factors that can contribute to variation of female mate choice. Many decades of research sought to understand ultimate mechanisms of female mate choice with proximate mechanisms receiving a lot more attention in recent years. For my thesis, I identify intrinsic and extrinsic factors that correlate with individual variation of female Xiphophorus nigrensis mate preference. I provide evidence that a female’s size (e.g. age and sexual experience) as well as male behavioral displays can predict female mate preference. Using genes associated with female mate preference (neuroserpin, neurologin-3), I identify four brain regions (Dl, Dm, HV, POA) that show significant differences in gene expression between females exhibiting high preference for males relative to females displaying little mate preference. Neuroserpin and neuroligin-3 gene expression within these brain regions are also positively correlated with female mate preference behavior. Two of these brain regions (Dm and Dl) integrate multisensory information and are found in the putative teleost mesolimbic reward circuitry; the other two regions (HV and POA) are involved in sexual behaviors. With the implication of the reward circuitry, I assess whether there are changes in dopamine synthesis (via tyrosine hydroxylase, TH) in dopaminergic brain regions associated with the degree of mate preference. I do not find evidence of rapid changes (within 30 minutes) of TH expression (i.e. dopamine synthesis) in dopaminergic brain regions related to variation in female mate preference. Collectively my results suggest that mate preference behavior in the brain may be coordinated not just through regions associated with sexual response but also through forebrain areas that may integrate primary sensory information, with no associated changes of a proxy for dopamine synthesis in dopaminergic brain regions.