My research focuses on the nature of the mechanism(s) that maintain sexual reproduction in populations of a New Zealand freshwater snail, Potamopyrgus antipodarum. This snail is characterized by the coexistence of both sexual and asexual individuals and is thus an appropriate system with which to examine the selective advantage of sex.

Recently, theory has shown that interaction between mutation and parasite pressure can maintain sex under less restrictive conditions than either mechanism acting alone. More specifically, the bottlenecking of asexual lineages caused by virulent parasitism will increase the strength of genetic drift and thus the rate of deleterious mutation accumulation in the lineage over that of an unparasitized lineage. This means that asexual populations afflicted by both mutations and parasites will be driven extinct much more quickly than they would with mutations or parasites alone.

If an interaction between parasitism and mutation accumulation is in fact acting to maintain sex in a natural population, asexual lineage longevity will decrease with the frequency of infection by specialized virulent parasites. I am testing this prediction by using mitochondrial DNA sequence information gene to estimate asexual lineage age and diversity within and between natural populations of a freshwater snail (Potamopyrgus antipodarum) that are characterized by a mix of sexual and asexual individuals and afflicted by varying frequency of infection by specialized castrating parasites (Microphallus spp.).