The vast majority of animals, plants, and fungi reproduce through outcrossing, or the exchange of gametes between two individuals. Why is this form of reproduction so common? Cloning, which only requires a single individual, is far more efficient. Evolutionary biologists have struggled with this paradox for 40 years. The Red Queen Hypothesis argues that outcrossing is maintained because it promotes the production of genetically diverse offspring that can escape parasitism. In contrast, cloned offspring are genetically identical to their parents and thus may be attacked by parasites that have adapted to infect their ancestors. The proposal will definitively test this hypothesis using a natural population of freshwater snails and their sterilizing parasites. The research will combine long-term field observations and experimental manipulations to determine if outcrossing snails gain an advantage over clonal snails in the presence of parasites. The results will provide one of the most extensive evaluations of selection on reproductive mode and genetic diversity in nature.
Broadly, the project aims to understand the power of genetic diversity to maintain parasite resistance in host populations. These findings will bear upon the work of researchers using applied disease systems to address human and animal health, crop management, and conservation. They will particularly benefit the management of populations in which diversity is declining (conservation) or manipulated (agriculture). Moreover, the investigators are committed to undergraduate education. They propose to translate their work into an interactive laboratory exercise in which to instruct undergraduates in the evolution of interactions between hosts and their parasites.
