Graduate Student, joint with Nicole King
The earliest branching metazoan phyla, sponges and cnidarians, produce both sperm and egg, suggesting that the animal sexual process has been conserved since the common ancestor of all living animals. In fact, the development of sex is often hypothesized to have been a prerequisite for the development of multicellularity. Meiosis, however, is clearly not an animal-specific invention; it has been observed throughout eukaryotes. Yet the sexual process found in all sexually reproducing animals contrasts with the reproductive strategies of protozoa, plants and fungi. To examine which aspects of animal reproduction are shared with their unicellular ancestors and which are distinct, I will study the reproductive process in choanoflagellates, the most closely related extant unicellular relative of animals.
Choanoflagellates are a diverse group of globally distributed marine and freshwater heterotrophic nanoflagellates that play a significant role in global carbon cycling. Choanoflagellates are capable of mitotic division, but no confirmed observation of meiosis, sex, or gametes has been made. In species that are isolated and then cultured, sex may be difficult to observe directly, because lab conditions may not accurately reproduce the natural environment and therefore may not be conducive to sex. My approach is instead to detect the genetic signature of past sexual reproduction that is written in patterns of current genomic polymorphism.