POLYMORPHISM IN A CYCLIC PARTHENOGENETIC SPECIES: SIMOCEPHALUS SERRULATUS

M. Yao Smith ¹ and Alex Fraser ¹

¹ Department of Biological Sciences, University of Cincinnati, Cincinnati, Ohio 45221

A survey of sixteen isozyme loci using electrophoretic techniques was conducted for three isolated natural populations and one laboratory population of the cyclic parthenogenetic species, Simocephalus serrulatus. The proportion of polymorphic loci (33%–60%) and the average number of heterozygous loci per individual (6%–23%) in the three natural populations were found to be comparable to those found in most sexually reproducing organisms. Detailed analyses were made for one of these populations using five polymorphic loci. The results indicated that (1) seasonal changes in genotypic frequencies took place, (2) apomictic parthenogenesis does not lead to genetic homogeneity, and (3) marked gametic disequilibrium at these five loci was present in the population, indicating that selection acted on coadapted groups of genes.