Biochemical Genetics of Mosquitofish. V. Perturbation Effects on Genetic Organization of Populations

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Abstract
Biochemical variation encoded by six loci was assessed for mosquitofish (Gambusia affinis) from 19 sites within a stream altered by water level reduction. Sites included temporary (isolated and nonisolated) pools and a main stream area. Populations exhibited significant genetic differentiation at two loci (isocitrate dehydrogenase-1 and phosphoglucomutase-2) and a significant association between demographic and genetic characters and between reproductive and genetic characters were minimal. Genetic differences were generally greater between juveniles and adults than between adult males and females. Patterns of allele distribution among sites were different for each adult group and juveniles, with only juveniles exhibiting a relationship between allele frequencies and geographic distance. Juveniles from sites in closer proximity were more similar, probably reflecting juvenile behavior rather than parental associations. Population substructure seems to be maintained during population disruption and colonization events.