On the affinities and systematic position of Pachytychius Jekel, a genus currently incertae sedis in Coleoptera, Curculionidae: Evidence from immature stages and the COI gene support its placement in Smicronychini

Abstract

The affinities and systematic position of Pachytychius Jekel, a genus currently incertae sedis in Coleoptera, Curculionidae, are assessed using new evidence from the immature stages and DNA sequences from the COI gene. The taxonomic history of genus Pachytychius denotes uncertainty in tribal placements from Erirhinini to various tribes of Curculioninae. In this paper, immature stages of genus Pachytychius are described and illustrated for the first time, including the mature larva of the type species, Pachytychius sparsutus (Olivier), and the larva and pupa of Pachytychius haematocephalus (Gyllenhal). The structural features of the larva and pupa of Pachytychius, as well as bionomic data, agree with those commonly found in subfamily Curculioninae and are consistent with a close relationship with Smicronyx Schoenherr. In addition, we used sequences from the 5′region of the COI gene, available in genetic databases, to test phylogenetic relationships of Pachytychius with other genera with which affinities had been suggested (77 terminal taxa including outgroups). Results from maximum likelihood and parsimony analyses agree: Pachytychius is not closely related to the erirhinines with pedo-tectal male genitalia, and belongs among the curculionine weevils, forming a clade with Smicronyx. Finally, the systematic position of Pachytychius suggested by the immature stages and the COI hypothesis results corroborated when adult morphological characters are re-evaluated, and can be extended to genus Aubeonymus Jacquelin du Val for its clear affinity to Pachytychius. The New placements are: Pachytychius Jekel, 1861 and Aubeonymus Jacquelin du Val, 1855 to Smicronychini from Curculioninae i. sed. (Curculionidae).