The South American genus Cnemalobus (Coleoptera: Carabidae: Cnemalobini): phylogeny and biogeographic analysis with the description of four new species from extra-Andean Patagonian mountains

Abstract

The carabid beetle Cnemalobus Dejean inhabits high and lowland grasslands of southern South America. Its highest diversity is found in the Patagonian Steppe, where it displays distribution patterns associated with latitude and elevation. Northern Patagonia, a large volcanic region with a complex geo-climatic history, exhibits elevated grades of endemism. However, much remains unknown regarding diversification and biogeographical patterns for most of their endemic groups. In this study, we describe new Cnemalobus species restricted to isolated volcanoes from these extra-Andean mountain systems. We assess their phylogenetic relationships by updating the genus´s phylogeny and conduct a Bayesian binary MCMC analysis upon the obtained phylogenetic tree to discuss their biogeographic distribution patterns. We also provide a taxonomic key to all currently known species of Cnemalobus from the Patagonian Steppe. Our phylogenetic analysis supports the monophyly of the new species Cnemalobus tromen sp. nov., Cnemalobus silviae sp. nov., Cnemalobus aucamahuida sp. nov., and Cnemalobus domuyo sp. nov. grouped with C. diamante and C. nevado, referred to as the “Extra-Andean” mountain lineage. Biogeographical analysis recognizes vicariant events as the most plausible explanation for the allopatric distributions of the new species. We hypothesize that these vicariant events could be related to climatic barriers that likely promoted speciation processes by generating geographical isolation in ancestral populations. Our findings significantly contribute to the biogeographic understanding of the Patagonian volcanic region, prompting new inquiries to unravel the speciation processes of the endemic biota in extra-Andean mountain systems.