DRIVERS OF SR EVOLUTION

The seminal receptacle or SR is the primary sperm storage organ in Drosophila and the site of sperm competition through displacement of resident sperm by second-male sperm immediately after mating. It is a long, coiled tube that can reach 8 cm in D. bifurca. In D. melanogaster, long sperm have a competitive displacement advantage in long SRs, while short sperm win out in short SRs. SR length is therefore a mechanism of cryptic female choice that selects for sperm length. We believe that SR length can be a driver of sperm length evolution, but it is unknown what drives evolution of SRs.

We are using comparative phylogenetic analysis in collaboration with Daniel Caetano to test the hypothesis that SR length is under sexual selection. Specifically, we are looking for an association between female remating rate as a proxy for the strength of sexual selection and SR length. We are also testing hypotheses about SR-sperm coevolution.

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What you're seeing here are the SRs of (clockwise from top left) D. persimilis, D. sulfurigaster, D. prosaltans, D. simulans, and D. ananasaae.