A new melanistic variant of the caterpillar hunterCalosoma wilcoxiLeConte, 1848 from Texas, United States of America and a preliminary phylogeny of the genusCalosomaWeber, 1801 (Coleoptera: Carabidae)

Abstract

AbstractTwo aberrant ground beetle (Coleoptera: Carabidae) specimens from the genusCalosomaWeber, 1801 were collected in Waco, Texas, United States of America, in 2012–2013. The specimens, which are morphologically most similar toCalosoma wilcoxiLeConte, 1848, but are dark blue-black instead of the typical metallic green. We employed DNA barcoding and phylogenetic methods to confirm the identities of the aberrant specimens. Preliminary phylogenetic analyses of cytochrome oxidase subunit 1 (COI) sequences of central Texas and southwestern species place the aberrant specimens with 100% confidence asC. wilcoxi.The new variant ofC. wilcoxipresumably occurs at low densities. Frequent collecting from 2011 to 2014 resulted in the discovery of only two of the aberrant coloured individuals among hundreds of typical green specimens. These specimens (to our knowledge) represent the first published record of melanisticCalosomafrom North America. While the majority of North American species in the genus are naturally black, two of the most widely distributed and abundant species,C. scrutator(Fabricius, 1775) andC. wilcoxi, are typically green. We sequenced the aberrant form as well as all species co-occurring with the new colour morph at the collection locality and used records from GenBank and the Barcode of Life Data System to generate a preliminary phylogeny of the genus, which suggested that some of the currently established subgenera are likely not monophyletic.