Molecular phylogeny, evolution and classification of the Hydrophilidae (Coleoptera)

The phylogeny and evolutionary history of the water scavenger beetles (Coleoptera: Hydrophilidae) are inferred from comprehensive analyses of DNA sequence data from the mitochondrial genes COI, COII and 16S and the nuclear genes 18S, 28S and arginine kinase. Bayesian and maximum parsimony analyses included 151 taxa, representing all subfamilies, tribes and subtribes that have ever been proposed in the family, as well as representatives of the hydrophiloid families Helophoridae, Hydrochidae, Spercheidae, Epimetopidae and Georissidae. The resulting well-supported trees strongly disagree with prior classifications of the Hydrophilidae, suggesting that the smaller subfamilies (Horelophinae, Horelophopsinae and Sphaeridiinae) are derived from within the larger Hydrophilinae. The existing tribal classification is more compatible with our results, but many significant differences are evident. Here, we present a new classification of the Hydrophilidae comprising 6 subfamilies and 12 tribes. Each subfamily and tribe is reviewed in detail with (i) a morphological diagnosis, including known or putative morphological synapomorphies, (ii) its taxonomic circumscription, including genera not included in our analyses, and (iii) a review of its general biology and geographic distribution. A new identification key to subfamily and tribe based on adult morphology is also provided. The newly adopted classification requires the following taxonomic changes: the subfamily Hydrophilinae sensu n. is redefined to include only the tribes Amphiopini stat.n. (removed from the synonymy with the Chaetarthriini), Berosini, Laccobiini, Hydrophilini and Hydrobiusini (= Sperchopsini syn.n.); the subfamily Chaetarthriinae stat.n. is removed from synonymy with the Hydrophilinae and includes the tribes Chaetarthriini and Anacaenini (= Horelophinae syn.n.); the Acidocerinae stat.n. (= Horelophopsinae syn.n.) and Rygmodinae stat.n. (= Andotypini syn.n., Borborophorini syn.n. and Tormissini syn.n.) are elevated to subfamily rank; and the subfamily Enochrinae subfam.n. is established for the genus Enochrus and its relatives. The implications for the morphological evolution, ecological transitions and biogeography of the family are discussed.