Taxonomic revision and phylogenetic analysis of the genus Oreodytes seidlitz (Coleoptera: Dytiscidae: Hydroporinae) based on larval morphology

The larval morphology of the dytiscid genus Oreodytes Seidlitz was investigated through a detailed analysis of 16 Nearctic and two Palearctic species. Many structural features, especially those of chaetotaxy and porotaxy of head capsule, head appendages, legs, last abdominal segment, and urogomphi, were found to be useful for taxonomic and phylogenetic comparisons. Within the tribe Hydroporini, it is proposed that Oreodytes shares a monophyletic origin with the genera Deronectes Sharp, Scarodytes Gozis, Nebrioporus Regimbart, and Stictotarsus Zimmermann. A tentative phylogenetic reconstruction of the genus Oreodytes, based on 29 larval characteristics, is provided. The classification of members of Oreodytes indicated by larvae is shown to be only partly reconcilable with the one indicated by adults. Once subdivided into three species-groups, Oreodytes now comprises four species-groups: the O. picturatus, O. obesus, O. scitulus, and O. quadrimaculatus species-groups. Oreodytes quadrimaculatus was found to share a monophyletic origin with the members of the O. picturatus and O. scitulus species-groups. The taxonomic status of the genus-name Neonectes J. Balfour-Browne is reconsidered as the larvae of N. natrix (Sharp) and N. babai Sato are revealed to be most similar morphologically to members of the O. scitulus species-group.