The family Epimetopidae (Coleoptera: Hydrophiloidea): review of current knowledge, genus-level phylogeny, and taxonomic revision of Eupotemus

Abstract

Epimetopidae are a small beetle family of the superfamily Hydrophiloidea, comprising 72 described species in three genera: the American Epimetopus Lacordaire, 1854 (56 species), Asian Eumetopus Balfour-Browne, 1949 (eight species) and African Eupotemus Ji & Jäch, 1998 (eight species, of which six are described as new here). In this study we illustrate and compare the adult morphology of all three genera and generate the first DNA sequences for Eumetopus and Eupotemus. The morphological data and sequences of four genes (cox1, 16S, 18S and 28S) are used to reconstruct phylogenetic relationships among genera. Both strongly support the monophyly of Epimetopidae, reveal Eumetopus as the earliest diverging taxon and Epimetopus + Eupotemus as a strongly supported clade with numerous synapomorphies. The reciprocal monophyly of Epimetopus and Eupotemus is strongly supported by DNA data but not in the morphological analysis which reveals Epimetopus paraphyletic. Eumetopus, despite being the earliest branching clade, is characterized by many unique derived structures, e.g. by the presence of the sperm pump in males (unique in Hydrophiloidea). The available data on the biology of Epimetopidae indicate that most species inhabit sandy to muddy margins of streams or rivers. Females of all three genera carry egg cases; Epimetopidae hence are one of three independent lineages of Hydrophiloidea in which this behavior evolved. Larvae are only known for Epimetopus and are characterized by morphological adaptations for feeding by piercing and sucking, a closed tracheal system and abdominal gills; larvae of Eumetopus and Eupotemus remain unknown and further research is needed to confirm whether they show the same adaptations as Epimetopus. The taxonomy of the African genus Eupotemus is re­vised, with six species described as new: E. bilobatus sp. nov. (Nigeria), E. cameroonensis sp. nov. (Cameroon), E. ophioglossus sp. nov. (Gabon, Togo), E. smithi sp. nov. (Côte d’Ivoire), E. taianus sp. nov. (Côte d’Ivoire) and E. uluguru sp. nov. (Tanzania). Eupotemus limicola Delève, 1967 is fixed as the type species of the genus according to ICZN (1999: Art. 70.3). New records of Eumetopus species are provided (E. acutimontis Ji & Jäch, 1998 from Vietnam, E. bullatus (Sharp, 1875) from India: Maharashtra, E. flavidulus (Sharp, 1890) from India: Maharashtra and Andhra Pradesh, E. maindroni (Régimbart, 1903) from India: Maharashtra and Gujarat, and E. weigeli Skale & Jäch, 2003 from India: Uttarakhand). The habitus of all species is illustrated. An updated checklist of the Epimetopus species is provided, and records of two specimens of the E. costatus group from Zambia and Saudi Arabia are considered to result from either accidental introductions or mislabelling.