Evolution of the host plant associations of the Anthonomus grandis speciesgroup (Coleoptera : Curculionidae): Phylogenetic tests of various hypotheses

A phylogenetic analysis was conducted of the Anthonomus grandis species gro up (Coleoptera: Curculionidae) and used to test various hypotheses concerni ng the evolution of these weevil species with their host plants. Phylogenet ic analysis indicated that the five species of the A. grandis species group comprise two major clades. In the first clade, A, grandis Boheman is the s ister taxon of A. hunteri Burke & Cate and A. mallyi Jones & Burke, and the second clade contains A. townsendi Jones & Burke and A. palmeri Jones & Bu rke. The proposed weevil phylogeny and knowledge of host associations stron gly support the hypothesis that the genus Hampea (Malvales: Malvaceae), and not cotton (Gossypium), is the original host plant genus of the A. grandis species group. Comparison of the phylogeny of the A. grandis group with th at of a previously published phylogeny of Hampea showed little congruence, suggesting that the species of weevils are associated with Hampea as a resu lt of host shifts and colonization processes, as opposed to co-speciation o r coevolution (par allel cladogenesis). Mapping habitat associations and ge ographic distributions onto the phylogeny of the A. grandis group indicate that weevil preference for general habitat type (Montane versus lowland hab itats) and geographic proximity of species of Hampea were probably the prin cipal factors responsible for observed associations of the weevils with the ir respective host plants. Possible characteristics of the A. grandis group , which may favor colonization as opposed to cospeciation processes in the association of its host plants, are discussed in light of these results.