Research Council of Norway, FRIBIO, 2010-2013 (project number 196554)
Description of Project:
One of the great puzzles in evolutionary biology is how the extreme diversity of mating systems has evolved under the constraints of a basically invariable mode of sexual reproduction; the fusion of two haploid gametes. A good illustration of this enigma is the large variation in promiscuity among songbirds (passerines), which is well documented by parentage analyses in hundreds of species, but still surprisingly poorly understood. The current project addresses this fundamental problem with a novel approach: viewing the sperm cell, the vehicle for male fertilization success, as the target of selection. Throughout the animal kingdom sperm cells are extremely diversified. In passerine birds they also show strong signatures of selection linked to their mating system. The project has four main objectives: 1) to test the utility of sperm phenotypes as indicators of phylogenetic differentiation and divergence, 2) to test if female promiscuity (i.e. sperm competition sensu lato) is a catalyst for sperm evolution, 3) to test if the two modes of postcopulatory sexual selection, sperm competition (sensu stricto) and female sperm choice, influences sperm evolution in different ways, and 4) to identify possible genomic and proteomic mechanisms involved in sperm competition and female sperm choice. In short, the project views the sperm as a sexually selected phenotype. This new approach will complement the traditional somatic analysis of evolutionary change in organisms and potentially provide new insights to our understanding of sexually driven speciation processes and mating system diversity.