Genetic variation in Hawaiian Drosophila. VIII. Heterozygosity and genic changes in isolated populations of D. engyochracea.

Drosophila engyochracea, an endemic Hawaiian fly found only in two, finite populations in Volcano National Park, has extensive electrophoretic heterozygosity on a par with that found in species with much wider distributions. A study of six polymorphic loci in both populations over an 18-month period revealed that the population in the more xeric environment is more dynamic genetically as well as more variable. In addition, genetic changes at one locus, Pgm, are correlaed to changes in an environmental moisture parameter. These findings confirm that migration is not necessary to maintain genetic variation in isolated population and demonstrate that D. engyochracea gene pools are susceptible to errors in Hardy-Weinberg equilibria during specific seasonal periods.