Comparative study of the Chatham Islands Odonata, II: Morphometric and molecular comparison between Xanthocnemis tuanuii Rowe, 1981 and X. zealandica (McLachlan, 1873) with notes on the taxonomic position of Xanthocnemis sinclairi Rowe, 1987 (Zygoptera: Coenagrionidae)

We compared Chatham Island endemic species Xanthocnemis tuanuii to its congenerics from the New Zealand South Island: X. zealandica (newly collected specimens) and X. sinclairi (type specimens plus newly collected material). Two independent tests were performed – geometric morphometrics and molecular. Both analyses were consistent in supporting the status of X. tuanuii as a good species. Species differed statistically in the following morphological traits: head (dorsal view), male appendages (dorsal, lateral, posterior and ventral views), thorax (dorsal view), and penis (dorsal and lateral view). In addition to the original diagnostic features (mainly shape of the male superior appendages), a new morphological character is suggested here which reliably distinguishes the species based on the shape of the inferior appendages. There was no statistical support for the species status of X. sinclairi. The only feature reported as diagnostic (lower lobe of male superior appendages) was found to be variable and insufficient to warrant the previously proposed taxonomic rank for X. sinclairi. Molecular analysis of specimens showing identical appendages to the X. sinclairi holotype grouped them with X. zealandica specimens. Therefore X. sinclairi is synonymised with X. zealandica.