BIOCHEMICAL-GENETIC DIFFERENTIATION AMONG SEED CHALCID SPECIES OF GENUS MEGASTIGMUS (HYMENOPTERA, TORYMIDAE)

The degree of genetic variability and the taxonomic status of adults o f 14 seed chalcid species of the genus Megastigmus was analyzed using electrophoresis on horizontal starch gel. Variability of chalcid popul ations with host tree was observed in 21 host species. A total of 13 e nzyme loci were considered. Seven of the loci were found to be polymor phic. The electrophoretic data strongly supported the adaptation of ea ch chalcid species to a limited number of congeneric hosts, and confir med the morphologically-based taxonomy of the genus. The resulting den drogram separated the chalcid species into three distinct groups, infe sting 1) Pinaceae spp., 2) Cupressaceae spp., and 3) Angiosperm spp., respectively. The highest level of overall genetic similarity was obse rved among the chalcid populations infesting conifers of the genera Ps eudotsuga and Abies. The genetic identity values observed among popula tions infesting 5 different Abies species tended to reflect the occurr ence of conspecific populations rather than that of distinct chalcid s pecies. Genetic identity was similarly important among the chalcid spe cies infesting seeds of Cupressaceae. By contrast, a large genetic dis tance was observed between two seed chalcids attacking a same host, Ro sa montana.