Labile Behavioral Evolution in a Genus of Agricultural Pests: the Rhopalosiphum Plant Lice (Hemiptera: Aphididae)

Abstract

I reconstructed the phylogeny of the economically important aphid genus Rhopalosiphum Koch to determine relative rates of evolution of 12 life-history and host-utilization traits. These behavioral characteristics affect the pest status of the 11 plant lice comprising this genus. The most parsimonious evolutionary trees suggest that none of the derived behaviors arose only once with no further change. All 12 behaviors are evolutionarily labile. However, the phylogenies are not well supported by bootstrap resampling analysis, and, according to the winning sites test, three of the 12 behaviors might have evolved only once with no further change. All three behaviors involve activities of the aphid on its host plant, whatever plant that might be. None of these possibly conservative characters involves choice of the host plant taxa themselves. Results suggest that these aphids might expand readily upon their current pest status because the historical colonization of their hosts has been an evolutionarily labile process.