Evolutionary assembly of the milkweed fauna: Cytochrome oxidase I and the age of Tetraopes beetles

The insects that feed on the related plant families Apocynaceae and Asclepi adaceae (here collectively termed "milkweeds") comprise a "component commun ity" of highly specialized, distinctive lineages of species that frequently sequester toxic cardiac glycosides from their host plants for defense agai nst predators and are thus often aposematic, advertising their consequent u npalatability. Such sets of specialized lineages provide opportunities for comparative studies of the rate of adaptation, diversification, and habitat -related effects on molecular evolution. The cerambycid genus Tetraopes is the most diverse of the new world milkweed herbivores and the species are g enerally host specific, being restricted to single, different species of As clepias, more often so than most other milkweed insects. Previous work reve aled correspondence between the phylogeny of these beetles and that of thei r hosts. The present study provides analyses of near-complete DNA sequences for Tetraopes and relatives that are used to establish a molecular clock a nd temporal framework for Tetraopes evolution with their milkweed hosts. (C ) 2001 Academic Press.