Spatio-temporal dynamics of host-shift in Henosepilachna vigintioctopunctata now in progress in Southeast Asia

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On the basis of field observations, food choice tests, rearing experiments and an analysis of mitochondrial DNA sequences, we studied spatio-temporal dynamics of host changes of Henosepilachna vigintioctopunctata in Southeast Asia. The primary host plants of this species are considered to be solanaceous plants. However, the populations utilizing an introduced legume "centro" were widespread in the southern part of the Malay Peninsula, Java, Sumatra, and western Kalimantan. They were not common or absent in more eastern areas. The DNA analysis suggested multiple origins of the centro-feeding trait in solanum-feeding populations in Southeast Asia. No convincing evidence was obtained for the divergence of H. vigintioctopunctata along the two host plants, or for the host change from solanum to centro. Even the centro feeding populations showed an extended larval period and small body size on centro, suggesting that they were not yet fully adapted physiologically to this plant.