Phylogeny of the beetle supertribe Trechitae (Coleoptera: Carabidae): Unexpected clades, isolated lineages, and morphological convergence

Abstract

Using data from two nuclear ribosomal genes and four nuclear protein-coding genes, we infer a well-resolved phylogeny of major lineages of the carabid beetle supertribe Trechitae, based upon a sampling of 259 species. Patrobini is the sister group of Trechitae, but the genus Lissopogonus appears to be outside of the Patrobini + Trechitae clade. We find that four enigmatic trechite genera from the Southern Hemisphere, Bembidarenas, Argentinatachoides, Andinodontis, and Tasmanitachoides, form a clade that is the sister group of Trechini; we describe this clade as a new tribe, Bembidarenini. Bembidarenini + Trechini form the sister group of remaining trechites. Within Trechini, subtribe Trechodina is not monophyletic, as three trechodine genera from Australia (Trechobembix, Paratrechodes, Cyphotrechodes) are the sister group of subtribe Trechina. Trechini appears to have originated in the continents of the Southern Hemisphere, with almost all Northern Hemisphere lineages representing a single radiation within the subtribe Trechina. We present moderate evidence that the geographically and phylogenetically isolated genera Sinozolus (six species in the mountains of China), Chaltenia (one species in Argentina and Chile), and Phrypeus (one species in western North America) also form a clade, the tribe Sinozolini. The traditionally recognized tribe Bembidiini sens. lat., diagnosed by the presence of a subulate terminal palpomere, is shown to be polyphyletic; subulate palpomeres have arisen five times within Trechitae. Anillini is monophyletic, and the sister group of Tachyini + Pogonini + Bembidiini + Zolini + Sinozolini; within anillines, we confirm earlier results indicating the eyed New Zealand genus Nesamblyops as the sister to the rest. Sampled New World Pogonini are monophyletic, rendering the genus Pogonus non-monophyletic. Tachyina and Xystosomina are sister groups. Within Xystosomina, the New World members are monophyletic, and are sister to an Australia-New Zealand clade. The latter consists of the genus Philipis as well as taxa not previously recognized as xystosomines: Kiwitachys, the “Tachys” ectromioides group, and “Tachys” mulwalensis. Within Tachyina, the subgenus Elaphropus is not closely related to other subgenera previously placed in the genus Elaphropus; we move the other subgenera into the genus Tachyura. Tachyina with a bifoveate mentum do not form a clade; in fact, a bifoveate mentum is found in Xystosomina, Sinozolini, Trechini, Trechitae and its sister group, Patrobini. Extensive homoplasy in the morphological characters previously used as key indicators of relationship is supported by our results: in addition to multiple origins of subulate palpomeres and bifoveate menta, a concave protibial notch has arisen independently in Anillina, Xystosomina, and Tachyina. Phylogenetically and geographically isolated, species-poor lineages in Trechini, Bembidarenini, and Sinozolini may be relicts of more widespread faunas; many of these are found today on gravel or sand shores of creeks and rivers, which may be an ancestral habitat for portions of Trechitae. In addition to the description of Bembidarenini, we present a diagnosis of the newly delimited Sinozolini, and keys to the tribes of Trechitae.