Phylogenetic Relationships of the Tribe Vatellini Based on Larval Morphology, with Description of Derovatellus lentus (Coleoptera: Dytiscidae: Hydroporinae)

The phylogenetic relationships and putative monophyly of the diving-beetle tribe Vatellini are explored based on a cladistic analysis of 37 taxa and 122 chaetotaxic and morphological characters from larvae. For this purpose, larvae of the genus Derovatellus Sharp are described and illustrated in detail, with particular emphasis on morphometry and chaetotaxy, with the later being unexplored until now. The results strongly support the monophyly of the Vatellini based on several unique larval characters. The terminal insertion of the primary seta UR8 on the second urogomphomere in members of Vatellini represents a reversal from the derived condition. Vatellini was recovered as the sister group of the Australian genus Antiporus Sharp (Hydroporini) based on the presence of: a spatulate nasale, pore PAe and elongate lateral spinulae on prementum. These characters, however, have a reduced value because all of them seem to have evolved several times independently within the Hydroporinae. The tribe Vatellini and its genera are diagnosed and compared with other hydroporine taxa, and interesting features are discussed. Vatellus Aubé is unique within Hydroporinae in the presence of secondary setae on the first antennomere and the first maxillary palpomere, and the one-segmented labial palpus. Derovatellus can be separated from almost every other Hydroporinae by the absence of seta LA1 on prementum and of secondary anterodorsal setae on femur.