Phylogenetic revision of the endemic New Zealand carabid genus Oregus Putzeys (Coleoptera : Carabidae : Broscini)

Abstract

This study explores the taxonomy and phylogeny of the New Zealand endemic carabid beetle genus Oregus. The genus was previously known from two species, Oregus aereus, which is widespread throughout the South Island, and Oregus inaequalis, which is highly restricted in its distribution (only found on the outskirts of Dunedin City) and prioritised as a category B threatened species by the Department of Conservation. Both morphology and mitochondrial DNA sequences were used for phylogenetic analysis. Twenty-six DNA sequences of partial cytochrome oxidase subunit 1 and NADH dehydrogenase subunit 1 were analysed. Analyses indicated four species – the existing O. aereus and O. inaequalis and two new morphologically cryptic species from the upper South Island, O. crypticus and O. septentrionalis. Oregus crypticus and O. septentrionalis form a basal clade and O. aereus is the most derived species. Oregus aereus remains the most widespread species, but the northern limit of its geographical range is now Porters Pass (approximately 150 km south of its historically assigned range). Male genitalic characters proved to be the most useful morphological characters. Oregus crypticus and O. septentrionalis are easily separated from O. aereus and O. inaequalis by external morphology. Differentiation between the two northern species was only possible by dissection of male genitalia or DNA sequencing. Oregus inaequalis remains highly restricted in its distribution (morphological analysis did not identify any new populations) and its species status is confirmed. Redescriptions are given for O. aereus and O. inaequalis and new descriptions and type designations are presented for O. crypticus and O. septentrionalis.