Sperm Evolution and Speciation in Littorina

ended

Sperm cells are the most morphologically diverse animal cells, but how does that diversity arise, and what are its evolutionary consequences? This project investigates the causes and consequences of divergence in sperm morphology between ecotypes in an intertidal snail species, Littorina saxatilis, where it was recently discovered that sperm length has diverged both between ecotypes and among island populations. I will perform transcriptomics on testes to identify sperm-length related genes, gene networks, and their relation to chromosomal inversions in the L. saxatilis genome. This robust technique allows me to determine the developmental origin and genomic causes of the sperm length differentiation. The project further performs experimental mating trials to measure the effect of sperm length per se on fertilization success, addressing a rarely-tested, long-standing assumption that sperm morphological divergence translates into reproductive barriers. Finally, I will build a genetically explicit model of sperm length divergence and its role as a reproductive barrier between populations. This model will allow me to explore how female promiscuity and the genomic architecture of sperm traits impact the long-term evolutionary potential for sperm divergence to occur and be a reproductive barrier. Thus this ambitious project addresses sperm length evolution from several biological disciplines and perspectives, to address the long-standing question of the evolutionary causes and consequences of sperm morphological diversity. This project also provides me with valuable training that will increase my competitiveness as I apply for faculty positions or for positions as an analyst supporting policy-makers. Specifically, I will learn learn ‘-omics analysis, an important skillset in biology that I currently lack, and a new and powerful programming language useful for big data.