MORPHOLOGICAL AND GENETIC DIFFERENTIATION IN APHIDS (APHIDIDAE)

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Abstract
Six species of aphids belonging to four genera were measured for 12 morphological features at five developmental stages. It was concluded that reliable identification of species based on morphological features is possible only at adult stages. Samples were also analyzed for seven enzymes by gel electrophoresis. There were no enzyme pattern differences among developmental stages in any species. Three enzymes, malic dehydrogenase, malic enzyme and tetrazolium oxidase, showed the same band pattern in all species. The other four, acid phosphatase, alkaline phosphatase, esterase and leucine-alanine peptidase, showed “diagnostic” patterns specific to a given species. All species are easily identifiable by their esterase pattern which could be confirmed by acid phosphatase, alkaline phosphatase, and leucine-alanine peptidase patterns. The enzyme pattern differences were used to establish a dendrogram of genetic relationship among species which was compared with a dendrogram of morphological similarities. The close genetic similarity among species suggests that significant adaptive differentiation leading to speciation may have occurred within the context of relatively few genie changes. This is compatible with speciation in aphids being due primarily to their obligate parthenogenetic reproduction, frequent bottlenecks (drastic reduction in number), and host plant specificity.