Meeting Abstract
Variation in life history traits and mating systems of sea stars make them useful systems for understanding how reproductive variation affects population genetic structure and molecular evolution. Here I compare and characterize the gonad transcriptomes of two closely related sister species from northeastern Australia with striking mating system differences. Cryptasterina pentagona individuals are gonochoric broadcast spawners with planktonic fertilization and the potential for strong sexual selection. By contrast, C. hystera individuals have similar morphology and natural history to C. pentagona (so similar that they were not recognized as a distinct species until their mating system differences were discovered), but are simultaneous hermaphrodites with internal self-fertilization and live birth, and limited potential for sperm competition (because they lack adaptations for sperm transfer between individuals) or sexual conflict (because outcrossing appears to be rare). Gonadal tissue of C. pentagona and C. hystera were collected from nine individuals to build and sequence RNA-seq libraries. These libraries were assembled with a de novo approach and analyzed with a customized pipeline. I found a ~10-fold difference in genetic diversity between species, which was consistent with other observations of high inbreeding and small effective population size in viviparous, brooding sea stars. The assembled genes included most but not all of the genes expected to be expressed in gametes and to play a role in fertilization (and evolve under sexual selection), including bindin and its receptors. I used a series of population genetic and phylogenetic tests to detect differences between species in the response to selection on coding sequence variation, which were similar to previously documented differences for bindin.
