Pretarsus and distal margin of the terminal tarsomere as an unexplored character system for higher-level classification in Cholevinae (Coleoptera, Leiodidae)

摘要

Cholevinae are well founded as a monophylum, but their internal phylogenetic relationships constitute a matter of longstanding dispute. The morphology has been the main source of information in most available phylogenetic studies on the subfamily. Most of the characters used, however, were limited to easily visible external structures and genitalia. Here we investigate the informative power of an unexplored character system for the higher-level systematics of Cholevinae: the morphology of the pretarsus and distal margin of the terminal tarsomere. We analysed and documented these structures in representatives of the five most species-rich tribes of Cholevinae (encompassing 13 subtribes) using scanning electron microscopy. We identified several diagnostic features and recognize potential synapomorphies at the tribal, subtribal and generic levels. The architecture of the median and empodial sclerites (including the empodial setae), the shape and composition of the medial projection of the distal margin of the terminal tarsomere, and the armature of the claws were considered a promising source of information for delimiting tribes and subtribes. Our data challenge the traditional view of a close proximity of Eucatopini and Ptomaphagini as well as a previously suggested synapomorphy of Leptodirini, and reinforce the monophyly of Ptomaphagini. This contribution is one of the rare comparative studies on the coleopteran pretarsus and one of very few evaluating the systematic usefulness of the distal margin of the terminal tarsomere in insects.