Phylogeny and evolution of the genus Ctenocolum Kingsolver & Whitehead (Coleoptera, Chrysomelidae, Bruchinae), with the description of three new species

Abstract

The seed beetle genus Ctenocolum Kingsolver & Whitehead is peculiar because its preferred host Lonchocharpus Kunth (Fabaceae) is not preyed upon by other bruchine species. This study investigates the phylogenetic relationships and evolution of this genus and of its species groups, while providing the description of three new species and of the male of C. biolleyi Kingsolver & Whitehead. To infer phylogenetic relationships, a character matrix of 40 morphological characters was assembled and analysed using both parsimony and Bayesian inference. Ancestral state estimations of host plant use and biogeography analyses were also performed. A total of 22 species were examined: 16 Ctenocolum species (including the three new ones) and six outgroup bruchine species (from genera Caryedes Hummel, Meibomeus Bridwell, Pygiopachymerus Pic and Pachymerus Thunberg). All resulting trees support the monophyly of the genus Ctenocolum. Three synapomorphies characterize the genus: (i) head with frontal carina enlarged at base, (ii) male pygidium truncated apically, and (iii) lateral lobes of tegmen with dorsal process. The two known species groups are also recovered monophyletic in the parsimony analyses. The following three species are described: Ctenocolum inmaculatus Manfio & Ribeiro-Costa sp. nov. (Type locality: Venezuela, Guarico), which belongs to the group tuberculatum; Ctenocolum nigronotus Manfio & Ribeiro-Costa sp. nov. (Type locality: Porto Rico, Mayaguez) and C. pallidus Manfio & Ribeiro-Costa sp. nov. (Type locality: Republic of Guyana), which belong to the group podagricus. Finally, we present colored illustrations of dorsal patterns and male genitalia for these three new species and C. biolleyi in addition to an updated key for the genus Ctenocolum.