Host-related morphological variation within Myzus persicae group (Homoptera: Aphididae) from Japan

There have been independent long-term studies of tobacco-adapted populations of Myzus persicae in Japan and Greece, but until now no direct comparisons have been made between them. In Japan, as in Greece, tobacco aphids can reproduce sexually to some extent so that there is the potential for hybridisation with M. persicae from other plants on their common primary host, the peach. To determine whether Japanese tobacco aphids agree morphologically with those in Greece, and hence fit the concept of M. persicae ssp. nicotianae, multivariate morphometric analysis was applied to 16 clones of M. persicae s.lat. from various localities in Japan. The clones represented 14 different colour-esterase forms collected from tobacco and other crops over a 20-year period and kept in laboratory culture. The analysis discriminated most of the clones from tobacco from those collected on other crops. When Japanese samples were analysed together with those from Greece, the tobacco-feeding clones of both countries had a similar pattern of morphometric correlations, discriminating them from those on other crops, even though they were reared under different conditions. Thus, the genomic integrity of M. p. nicotianae seems to be preserved across a wide geographical scale and even in regions where interbreeding can occur. The possible origin and evolution of the tobaccoadapted subspecies are discussed.