Patterns of genotypic diversity in Czechoslovakian Daphnia

Abstract

Patterns of allozyme diversity were studied in Czechoslovakian populations of six Daphnia species to ascertain their mode of reproduction, the incidence of interspecific hybrids, and the relationship between genotypic diversity and habitat permanency. All six species were shown to reproduce by cyclic parthenogenesis. D. pulex and D. pulicaria, two closely related species whose taxonomic validity has been questioned, showed little polymorphism but diagnostic gene substitutions confirmed their distinctiveness. Populations of the pond species D. magna and D. longispina were commonly polymorphic but showed infrequent Hardy–Weinberg deviations. D. galeata from pond habitats showed a moderate incidence of deviations, but reservoir populations showed consistent heterozygote excesses and non-random multilocus associations. F1 hybrids and backcross progeny between D. longispina and D. galeata were detected in a third of the ponds and comprised, on average, 5 per cent of the local populations. In reservoirs, F1 hybrids between D. galeata and D. cucullata were common, with a genotypically diverse group of hybrids dominating one site.