Phylogeny, evolution and classification of the giant water scavenger beetles (Coleoptera: Hydrophilidae: Hydrophilini: Hydrophilina)

The hydrophiline subtribe Hydrophilina is composed of nearly 200 described species, including all known water scavenger beetles over 15 mm in length. Found in all biogeographic regions, the lineage is the most recognizable group in the family due to its large size and presence of a sternal keel. A phylogenetic analysis of Hydrophilina based on 80 adult morphological characters supports the reciprocal monophyly of most genera, including Tropisternus Solier, Sternolophus Solier, Hydrophilus Geoffroy, and Hydrobiomorpha (s. str.) Blackburn. The monophyly of Hydrochara Berthold was not resolved. The subgenus Brownephilus Mouchamps of the genus Hydrobiomorpha is elevated to generic rank and suggested to subtend (Hydrophilus+Hydrobiomorpha (s. str.)). A newly discovered taxon from Venezuela, Protistolophus spangleri gen. et sp. nov., is described and resolved as the earliest diverging lineage of the Hydrophilina. A revised generic classification of the Hydrophilina is proposed, including a key and revised diagnoses for each genus. The evolution of giantism and complex secondary sexual characters are discussed in the context of the newly developed phylogenetic hypothesis.