Enzyme variability in natural populations of Daphnia carinata king.

Fifteen populations of the cladoceran crustacean, Daphnia carinata, were examined for allozyme variation at sixteen gene loci. Individuals of this cyclic parthenogen were heterozygous at only 2.1 per cent of their loci. Large differences in gene frequencies existed among the populations. Within populations genotypic frequencies were in good agreement with Hardy-Weinberg expectations, and remained stable during annual cycles of population growth. Strong linkage disequilibrium was observed between the allelic variants at two leucine aminopeptidase loci in certain populations, suggesting that the loci are tightly linked and that populations of D. carinata are founded from few individuals.