Mitochondrial DNA phylogeny and the evolution of host-plant use in palearctic Chrysolina (Coleoptera, Chrysomelidae) leaf beetles

The genus Chrysolina consists of specialized phytophagous leaf-beetles (Col eoptera, Chrysomelidae) with feed on several plant families. Then is no exp licit phylogenetic hypothesis available for this genus, which includes 65 s ubgenera and more than 400 species with a wide distribution. We obtained 83 9-bp sequence data from the 16S rDNA and cytochrome oxidase subunit I(COI) mitochondrial genes. Thirty Chrysolina taxa representing eight host-plant a ffiliations, two species of the closely related genus Oreina, and two outgr oups were sampled. These data sets were used separately and combined to obt ain the mitochondrial cladogram of the group using maximum-parsimony and ma ximum-likelihood criteria. The results were compared to current proposals f or Chrysolina systematics that are based on morphological, ecological, and karyological data. The trees obtained were in the most part congruent with the proposed ancestral association of Chrysolina to Lamiaceae based on chro mosome number in several lineages. A minimum of five host-plant switches fr om the ancestral state inferred at the family level and two at the subclass level suggests the absence of parallel evolution of beetles and their host plants, Another switch leading to oligophagy at the family level was deduc ed to have occurred in the lineage of the subgenus Chrysolina s.str.