Microsatellite DNA and behavioural studies provide evidence of host-mediated speciation in Myzus persicae (Hemiptera: Aphididae)

In many parts of the world, the tobacco specialist Myzus persicae nicotianae is isolated from the generalist Myzus persicae s.s. because either or both taxa reproduce parthenogenetically. Here we investigated how the genomic integrity of the tobacco specialist is maintained in Greece, where both taxa have a bisexual generation on peach. Microsatellite DNA analysis revealed greatest genetic divergence between populations in tobacco-growing regions and those in a region where tobacco is not cultivated. This was irrespective of reproductive mode, which has an important effect on population structure. Bayesian clustering and admixture analyses split the aphid genotypes into three groups, corresponding with persicae, bisexual nicotianae and unisexual nicotianae, respectively. Genetic distance parameters showed strong regional differentiation but marked year-on-year stability, indicating low interpopulation migration. Assortative mating between taxa is promoted by differences in the daily rhythm of female signalling behaviour, with peak activity coinciding with periods of consubspecific male searching activity. Males showed greater attraction to the sex pheromone of their own subspecies. Thus, despite relatively low overall genetic differentiation, processes are in place facilitating further genomic divergence and eventual speciation. (C) 2007 The Linnean Society of London.