HOST-PARASITE INTERACTIONS - INFECTION OF COMMON CLONES IN NATURAL-POPULATIONS OF A FRESH-WATER SNAIL (POTAMOPYRGUS-ANTIPODARUM)

The Red Queen hypothesis for the maintenance of cross-fertilization requires that parasites evolve to infect disproportionately the most common of local host genotypes and prevent their spread. Here we test the idea that digenetic trematodes are non-randomly infecting the common clonal genotypes in four populations of the freshwater snail Potamopyrgus antipodarum. The results show that the most common clone was significantly over-infected in one population, significantly under-infected in two other populations, and proportionately infected in the fourth population by the predominant castrating parasite. We show that, given the expectation of time lags in the system, these results are consistent with expectation under the Red Queen theory.