Taxonomic revision and cladistic analysis of Atrichonotus Buchanan (Coleoptera: Curculionidae)

In this study Floresianus Hustache and Floresianellus Lanteri are considered synonyms of Atrichonotus Buchanan, because they are evolutionary grades within the same genus. Atrichonotus is redescribed, its six species are included in a key and redescribed and a cladistic analysis of these species with Graphognathus Buchanan and Naupactus Dejean as outgroups is presented. The cladogram obtained using the computer program PAUP is asymmetrical and shows the following evolutionary sequence: A. taeniatulus (Berg), A. pacificus Kuschel, A. obscurus (Hustache), A. marginatus (Hustache), A. convexifrons (Hustache), and A. sordidus (Hustache). Two additional analyses were done, one deleting the two characters that have the same character states in Atrichonotus and Graphognathus, and another including the genus Eurymetopus as a terminal taxa. The first analysis resulted in three equally parsimonious cladogram; one of them is identical to that obtained when all characters were included, and in the other two cladograms A. pacificus is the most plesiomorphic species. When Eurymetopus was considered as another terminal taxa, it became the sister group of A. sordidus. We believe that the possibility of A. pacificus being the most plesiomorphic species of Atrichonotus, and the possibility of Eurymetopus being a member of this genus, should not be excluded. The paper includes habitus photographs, line illustrations of the diagnostic external and genital characters of Atrichonotus and Graphognathus, a detailed analysis of the character evolution, and a biogeographical discussion. The latter attempts to explain the presence of A. pacificus in Chile and the facts that could have favored the speciation of Atrichonotus.