A phylogenetic analysis of beetles belonging to the Trechus ovipennis group (Coleoptera: Carabidae)

This study explores the biogeographic distribution and evolutionary relationships of beetles belonging to the Trechus ovipennis species group. Trechus is a Holarctic genus of ground beetles that are adapted to cold, damp microhabitats and thrive in high elevations next to flowing water sources. The ovipennis species group is restricted to the North American west, where they range along the coast from Alaska and British Columbia south to Riverside County in California, with some endemic species inhabiting mountain ranges eastward in Arizona and inland Southern California. Species examined as a part of this study include Trechus ovipennis, Trechus pomonae, Trechus humboldti, Trechus arizonae, and Trechus alinae. We have attempted to define the biogeographic distribution for each of these species based on locality data from museum specimens and from our own field collecting efforts. A map with the biogeographic distributions for each species is presented. A molecular phylogeny was constructed using fragments of mitochodrial protein-coding gene cox1, ribosomal mitochondrial gene 16S, protein-coding nuclear gene Topoisomerase I, and ribosomal nuclear gene 28S. Additionally, microscopic examination revealed useful comparative morphological features, including length and width of head and elytra in relation to that of the pronotum, overall size and shape of body form, coloration of body and appendages, size and shape of the pronotum, convexity of the elytra, development and number of elytral striae, number and position of setiferous punctures on the 3^rd elytral interval, and features of the male genitalia. Monophyly of the species group and phylogenetic relationships among the included species were inferred from analyses of both molecular and morphological data.