9310374 Case Parasites maybe responsible for the maintenance of reproductive patterns, "Red Queen" hypothesis. In some systems asexuals have significantly more parasites than sexuals, but pilot data for the current studies show just the opposite pattern. However, it is impossible to use such data as a direct test of the Red Queen hypothesis since a variety of mechanisms, such as parasite transmission dynamics and virulence, can shape patterns of parasite distribution in the wild. The Red Queen hypothesis generates predictions about which mechanisms must be important in host/parasite interactions in order for asexuals to be favored: i) host susceptibility must be the most important determinant of parasite distribution in a population; ii) host susceptibility must be genetically determined; and iii) host susceptibility must be frequency-dependent, with the most common genotype becoming the most susceptible over time. The current study will experimentally test these predictions in the sexual/asexual gecko system. %%% Understanding the maintenance & development of major demographic properties, such as mode of reproduction among species, is a major goal of population biology. However, theory predicting that parthenogenetic forms are rare because they are more susceptible to parasites has largely remained untested in complex ecological situations. The present research takes an ecological perspective to a fundamental problem in evolutionary biology. ***
