Taxonomia e filogenia de Plistonax Thomson, 1864 (Coleoptera, Cerambycidae, Lamiinae)

Abstract

The family Cerambycidae is one of the most diverse groups of the order Coleoptera, comprising about 36,000 species. The taxon is divided into eight subfamilies, and Lamiinae is the most representative, with more than 21,000 species distributed in 87 tribes. One of these tribes is Acanthoderini, which includes 70 genera, mostly from the Neotropical region. The tribe is broadly studied in taxonomic terms, but there are few efforts oriented to phylogenetic approaches, since just two genera have been studied with cladistic methodology. Plistonax is one of Acanthoderini genera without a phylogenetic framework, comprising eight species from South America. The genus was proposed without diagnostic characteristics, and therefore the allocation of its species is a difficult exercise in classification, resulting in frequent taxonomic interchange with other genera of similar morphology. Therefore, it is necessary to expand the taxonomic knowledge of Plistonax, as well as to assess its validity as a natural group through a phylogenetic study. In this context, this work aims to determine the taxonomic limits of the Plistonax, by means of a phylogenetic analysis based on morphological data. A maximum parsimony analysis was implemented for including 24 species, using 52 characters. Discrete and continuous characters were analyzed in three distinct matrices: with continuous characters discretized, with continuous characters not discretized, and without continuous characters. The analyses showed that Plistonax is a polyphyletic group, with two lineages: one represented by Plistonax insolitus, and another for the other seven species of the genus, with the addition of three species of other genera (Acanthoderes (Acanthoderes) ariasi, Melzerus difficilis and Psapharochrus signatifrons). Based on results, we redelimit Plistonax to include only 10 species, with three new combinations, and Pl. insolitus is considered incertae sedis in Acanthoderini. On this new conformation, we provide a redescription for the genus Plistonax, as well as for part of its species. An identification key was elaborated for the genus, and records of geographical distribution of its species were listed.