Advisors: H. Kern Reeve and Paul Sherman
Start Date: Fall 2003
Sex is so ubiquitous and familiar that we take it for granted as a fact of the animal world. Actually, sex is a highly inefficient mode of reproduction whose prevalence is deeply troubling from an evolutionary perspective. In theory, a female producing apomictic clones should do twice as well as her sexual rivals, who must search for males in order to enter a meiotic lottery that is certain to strip them of half their genetic contribution to each offspring. Despite its theoretical disadvantages, sex is common in most animal groups, and asexuality is rare. Obligately parthenogenetic clades are found only at the tips of phylogenetic trees, suggesting that the complete renunciation of sex is rapidly followed by some evolutionary catastrophe whose nature is not fully understood.
Rotifers of the Class Bdelloidea are an exception to this rule, as they appear to have persisted and radiated in the absence of sex for at least 40 million years. The success of the bdelloid rotifers may hold the key to the function of sex in other animals. In particular, I am interested in the hypothesis that sexual organisms present a constantly changing genetic target for their co-evolving parasites and pathogens, whereas clones suffer from identical genetic vulnerabilities that allow a well adapted enemy to cause universal devastation. Under this ‘Red Queen’ hypothesis, the parthenogenetic bdelloid rotifers must possess some unique mechanism for dealing with parasites in the absence of sex. I run a small microecology lab at Cornell, where my undergraduate assistants and I have been culturing rotifers and their parasites. We are examining a metapopulation model that suggests the bdelloids may escape their co-evolved parasites by dispersing in space and time, removing the need for sexual diversity.
I have a second research interest in the evolution of costly ritual in humans, and I have published on the adaptive function of genital mutilation behavior in pre-industrial societies. I also teach and organize animal behavior sections at Cornell, with a particular focus on writing. My advisers are Paul Sherman and Kern Reeve.