Genes involved in sperm development (spermatogenesis) tend to evolve rapidly, but some aspects of spermatogenesis are highly conserved and essential for fertility. These contrasting patterns may result from varying intensities of different selection pressures across the developmental process of spermatogenesis. Rapid spermatogenesis evolution may also have important consequences for sex chromosome evolution and male hybrid sterility, an important reproductive barrier between incipient species. During my Ph.D., I investigated the causes and consequences of rapid spermatogenesis evolution. This work is in collaboration with Erica Larson.

Murine rodents include rats and mice from Europe, Africa, Asia, and Australia. They comprise the most rapid radiation in mammals and exhibit remarkable diversity in reproductive traits. This diversity is thought to reflect variation in the intensity of sexual selection among species, but this had not been tested in a phylogenetic framework. At the molecular level, genes involved in reproduction tend to evolve rapidly, but it is unclear if rapid molecular evolution is predominantly due to positive selection on genes underlying rapidly evolving reproductive traits. To test this, I am combining whole exome data collected from species spanning the murine radiation with previously published male reproductive data to perform phylogenetic comparative analyses of both phenotypic and molecular evolution on murine rodent reproductive traits.

Vision is critical for foraging, avoiding predators, and finding mates in many species. Despite the importance of vision, visual acuity is highly variable across species, and the relative contributions of different selective pressures and developmental processes to this variation are still unclear. Many vertebrates have specialized high visual acuity regions in the retina, such as an area centralis (region of high retinal ganglion cell density), a horizontal streak (elongated region of high density stretching across the retina), or a fovea (physical indentation in the retina surrounded by a region of high density), that may be associated with different ecological conditions. Many have proposed hypotheses regarding the ecological drivers that select for these retinal specializations. For example, the fovea is thought to help with vision in complex three-dimensional environments or dim light environments. However, these hypotheses have not been tested using phylogenetic comparisons across multiple species. In ray-finned fish, these specializations have evolved repeatedly in different clades, providing a powerful system in which to test these hypotheses. I am using phylogenetic comparative approaches to uncover the ecological selective pressures associated with retinal specializations in ray-finned fish.