A remarkable new species of the genus Hydaticus from Madagascar, with an identification key for Malagasy species of the genus (Coleoptera: Dytiscidae: Dytiscinae)

Abstract

Summary Hydaticus (Prodaticus) mangamanga n. sp. is described from a single sampling site in the south-eastern part of Madagascar Central Highlands, near Ranomafana. The new species is unique among the known species of the genus Hydaticus in that the last visible abdominal ventrite is strongly modified and differentiated between sexes, and is also quite unusual in paramere configuration. Analysis of partial CO1 sequences revealed that H. mangamanga belongs to the leander-group and is genetically close to the Malagasy region endemic H. inconspicuus Régimbart, 1895 stat. rev. with only around 1.5% of sequence divergence, providing the first instance of a sister-group relationship between two Hydaticus species endemic from the Malagasy region. However, morphologically these two species differ considerably. They are illustrated (habitus, structures, male genitalia) and compared in detail. Collecting circumstances for H. mangamanga are described and a map of its known distribution is provided. A lectotype is designated for H. inconspicuus; this name is re-established as valid for this species, and the name H. kolbei Branden, 1885 used in the recent literature is considered of doubtful identity. An identification key is provided for all Hydaticus (Prodaticus) species known from Madagascar, with accompanying illustrations of median lobes of aedeagus in lateral view.