Sexual adaptation across evolution: the neural basis of female sexual motivation

What are the molecular mechanisms that determine intra- and inter-species behavioral variation?

We propose to address this key outstanding question in evolutionary neuroscience by exploring a striking example of adaptive evolution of female sexual behavior.

Comparing two closely related nematode species that use different mating strategies, we discovered that while androdioecious (hermaphrodite-male) C. elegans hermaphrodites are indifferent to males, dioecious (female-male) C. afra females exhibit a pronounced sex drive, actively engaging in and initiating mating.

Importantly, we found that under induced reproductive pressure, the passive hermaphrodites switch to female-like behavior, suggesting the existence of a suppressed neuronal circuit.

In this proposal, we will employ an evolutionary comparative approach to deconstruct the neural basis of female sexual motivation, by addressing three objectives: (1) Explore and quantify the extent and molecular basis of female sexual motivation in C. afra. (2) Characterize the neuronal underpinnings of sexual attraction, by mapping gene expression, connectivity, and network dynamics in females, and (3) Investigate how mating pressure promotes sexual adaptation in C. elegans hermaphrodites, by monitoring the evolving changes in genetics, epigenetics, and the neuromodulatory network in transition states from passive to active sexual behaviors.Our suggested program challenges long-held assumptions about the role of female sexual motivation, which despite its complexity remains understudied compared to male mating behaviors.

Our unique approach, utilizing the power of C. elegans alongside tool building for investigating C. afra, will not only unveil the molecular mechanisms governing the emergence of novel female sexual behaviors but also create a blueprint for understanding their evolution.