Jumping to new hosts: the diversification of flea beetles (Coleoptera: Chrysomelidae: Alticini) in the context of their host plant associations

Flea beetles (Alticini) represent one of the most diverse groups within the family Chrysomelidae and are associated with more than 100 different plant families. Conspicuously, only 10 genera account for about a quarter of flea beetle diversity, whereas about 380 genera each comprise less than ten species, indicating different rates of diversification within the Alticini. Here, we reconstructed the phylogenetic relationships of 608 species in 101 Alticini genera using mitogenomes and cytochrome oxidase I, and applied several frameworks of clade-specific diversification rate analyses. Increased diversification rates were consistently detected in the cosmopolitan genera Altica and Longitarsus, the Palearctic genus Phyllotreta, and in neotropical taxa of the subtribe Oedionychina. In addition, we tested whether the evolution of specialized interactions with plants of the order Brassicales influenced the diversification of Phyllotreta and Psylliodes flea beetles. Specialization on Brassicales was only associated with increased diversification rates in Phyllotreta but not in Psylliodes. Our results indicate that host associations per se do not explain different diversification rates and lay the groundwork for investigating the evolutionary drivers of rapid radiations in Alticini.