Larval morphology of the enigmatic genus Queda Sharp, 1882 supports monophyly of Hydrovatini (Coleoptera, Dytiscidae)

Abstract

A comprehensive phylogenetic analysis of larval characters, including for the first time members of the rare and enigmatic genus Queda Sharp, 1882 was conducted to test the hypotheses of monophyly and relationships of the tribe Hydrovatini within the diving-beetle subfamily Hydroporinae. Our results indicate that Hydrovatini (including both Queda and Hydrovatus Motschulsky, 1853) is monophyletic and unambiguously supported by the absence of the primary pore PAo on the parietal and by the antennal process (commonly identified as A3?) arising from the base of the antennomere 4. This result agrees with the original concept of the tribe introduced more than 100 years ago but challenged by some authors. Our study supports the inclusion of Hydrovatini in a clade of ancestral hydroporine lineages together with Laccornini, Laccornellini and Pachydrini. Within this clade, Hydrovatini is sister to Pachydrini based on the shared absence of an occipital suture in instars II?III, although with weak support. The third-instar larva of Queda is diagnosed and described. It is characteristic in the broad and semicircular shape of the nasale, the maxillary cardo partially fused to the stipes, the presence of setiferous tubercles on the cephalic capsule and abdominal segment VIII, and the subcylindrical and relatively well-developed galea which, interestingly, is somewhat more developed than those exhibited by other hydroporines.