Dissertation Research: Patterns of Reproductive Isolation in the Brachionus plicatilis Species Complex (Rotifera)

Yale University, New Haven CT

Investigators

Abstract

0105040 Rice Speciation involves the splitting of a population, such that the members of either of the new populations are unable to mate and produce fertile offspring with the members of the other. In nearly all cases, little is known about exactly what biological changes are responsible for this reproductive isolation. The proposed research will address this question using the rotifer Brachionus plicatilis, populations of which inhabit salt lakes and coastal ponds worldwide and exhibit a range of abilities to interbreed. First, two genes from B. plicatilis will be sequenced to determine genetic divergences and the evolutionary relationships (i.e., a family tree) between different populations. Second, representatives of different populations will be crossed and the fate of the hybrids followed closely. The following specific questions will be addressed: What trait differences causing reproductive isolation arise first (i.e., what initiates speciation, and what finalizes it)? What evolutionary processes are responsible for their divergence? How rapidly can and does a new species originate? Understanding the biology underlying the evolution of reproductive isolation is critical to a general understanding of the processes responsible for producing biological diversity. Furthermore, many groups of organisms, including rotifers, have "hidden" species, populations that are fully reproductively isolated but do not look distinct and are thus not recognized as distinct species in most surveys. In addition to determining the true number of species currently lumped together as "Brachionus plicatilis", this study will provide insight into the mechanisms by which hidden species arise and how common they are, an understanding of which is essential to any accurate assessment of biodiversity.