DNA Barcoding versus Morphological Variability of Pterostichus brevicornis brevicornis (Kirby, 1837) (Coleoptera, Carabidae) in the Arctic and Subarctic

SIMPLE SUMMARY: Taxonomic studies on a polymorphic species inhabiting a region with relatively uniform environmental conditions (e.g., the Arctic) should involve an integrative approach. Ground beetles such as the subgenus Cryobius of the genus Pterostichus are a successful group in expansion in the tundra biome. The current taxonomy of Cryobius species is unclear and could be considered an obstacle to ecological studies; knowledge of their distribution patterns in the Arctic is rather limited. In this study, the first report on the phylogeography and phylogeny of the most abundant tundra subspecies, P. (Cryobius) brevicornis brevicornis (Kirby, 1837), within its continuous range throughout northern Eurasia and North America is presented. The results indicated that the male genitalia morphology of P. b. brevicornis from Eurasian populations shared a higher geographic variability compared with the pronotum shape and the mitochondrial DNA sequences. ABSTRACT: The geographic patterns of genetic and morphological variability in ground beetles were examined throughout Northern Eurasia and North America using the most abundant circumpolar tundra subspecies, Pterostichus (Cryobius) brevicornis brevicornis (Kirby, 1837), as a model. Phylogenetic structure was assessed on the basis of a Bayesian approach using two DNA markers (partial sequences of the COI and 28S rRNA genes), while phylogeographic patterns and population genetic diversity were estimated using the COI gene only. Morphological patterns were analysed using elliptical Fourier coefficients that were calculated based on the pronotum and male genitalia shape outlines. The subspecies shares 23 COI haplotypes throughout its entire circumpolar range, while eight haplotypes of 28S rRNA were detected in Northern Eurasia. Phylogenetic analysis did not reveal subdivided species lineages with strict geographical imprint. The network, F(ST) and uncorrected pairwise divergence analyses showed that the genetic distances between populations increase by longitude from Northeastern Asia to Europe. The genetic variability among the five studied geographical population groups of P. b. brevicornis was relatively high. The MANOVA showed significant regional divergence between local populations in Northern Eurasia based on both morphological markers, but only male genitalia variability was geographically structured. Neither the pronotum shape nor the male genitalia shape aligned with the phylogeographic patterns discovered on the basis of COI sequences. The genetic (COI) marker had more variation within, rather than among, population groups in addition to morphology of pronotum but not male genitalia.