Title: Postcopulatory sexual selection and the evolution of reproductive traits with a focus on sperm morphology.

Speaker: Dr Zeeshan Syed Ali, Syracuse University

Timing: 20 January 2022 7PM-9PM IST

Lab: https://www.unil.ch/dee/kawecki-group

Abstract

Sexual selection is the primary driving force in the evolutionary diversification of extreme traits (usually in males) through intrasexual contest (armaments) or intersexual choice (ornaments). Whereas the most obvious examples of armaments (e.g., antlers, beetle horns) and ornaments (e.g., body patterning, songs, courtship behavior) have been studied in great details for pre-copulatory selection, i.e., selection on mate acquisition, the most extreme evidence of trait diversification is found in sperm length in the genus Drosophila which is driven by postcopulatory sexual selection (PSS), i.e., selection on fertilization success. However, studying the evolution of such traits have been challenging and surprisingly little is known about the selective processes underlying its tremendous diversification throughout the animal kingdom. This is especially true for internally fertilizing species, where PSS depends on complex interactions between rival males and between the ejaculate and the female reproductive tract which are difficult to investigate in-vivo. In this discussion, I would present some of the studies I have been (and continue to be) involved in that tries to address some of the questions regarding ejaculate- female interactions and the evolution of sperm traits under PSS. First, I would show how changing the intensity of PSS in a microevolutionary timescale can result in the evolution of multivariate male and female reproductive traits. Then we'll zoom out to macroevolutionary time and discuss the evolution of a novel spermatogenetic mechanism, 'sperm looping', in the face of ecological and sexual selection in two groups of species in the Drosophila genus, and the adaptive benefits and evolutionary costs of the mechanism. Lastly, I'll present some ongoing research about uncovering the genetic mechanism that contributes to the variation in sperm morphology.

Together, I would try to emphasize the need for an integrative approach of synthesizing studies in macroevolutionary patterns, microevolutionary processes and genetic mechanisms to understand complex ejaculate-female interactions.

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