Evolutionary Cell Biology of Sperm

Evolution of gametic cells provides a microcosm of the interface between natural selection and sexual selection, including sexual conflict between the fitness interests of the sexes. We found Caenorhabditis‘ amoeboid sperm cells to have evolved radical size diversification, with a >50-fold range in volume across species. What other fitness-related traits associate with sperm size gigantism across phylogeny? What implications does sperm gigantism have for sexual selection and sexual conflict? Does harmful gamete-mediated reproductive interference affect multi-species community composition? How do subcellular sperm traits relate to cell size? How does temperature influence sperm cell fecundity? 

Shifts in reproductive mode have driven drastic changes in the genes responsible for sperm competition. The sperm gigantism of Caenorhabditis has led us to use electron microscopy peer inside these cells with even greater resolution, and the ectopic invasiveness of sperm cells suggests that they may provide a mechanism of reproductive interference competition between species. We are documenting temperature-dependent traits that differ between latitudinally– and phylogeographically-distinct strains of C. briggsae. We have interrogated the genetic basis of temperature-related traits with recombinant inbred lines (RILs) to QTL map  natural phenotypic differentiation thought to reflect local adaptation. We also are quantifying transcriptome responses to temperature and genotype.