Associations between parasitism and host genotype in natural populations of Daphnia (Crustacea : Cladocera)

摘要: 1. Numerous models of parasite−host coevolution have shown that parasitism could play a key role in wide range biological phenomena. One critical assumption underlying is natural selection acts on genetic variation for host susceptibility, but this has rarely been tested the wild. 2. Clonal hosts are particularly suitable detecting associations between genotypes and parasitism, because multi-locus gene complexes preserved during reproduction, following clonal selection, which differ at resistance loci may also show differences neutral marker loci. In study, allozymes were used to search (clones) within 25 cyclically parthenogenetic populations Daphnia. 3. Rates observed ranging from 0% 48% adult females, infection by microparasites was found significantly reduce fecundity. 4. Significant detected composition parasitized healthy Daphnia 12 populations, showing proportion individuals infected varies among clones. Six sampled repeatedly determine whether associated with temporal changes both frequencies population characteristics (Hardy−Weinberg equilibrium, genotypic linkage disequilibrium). Three six temporally showed structure consistent expectations parasite-mediated while other three did not. These latter all had low parasite prevalence (indicating intensities) and/or comprised primarily rare clones, thus limiting statistical power study detect effects. 5. The results presence likelihood contracting disease populations. genotype result or within-pond spatial arrangement prevalences. Either factor would lead modulation frequecies