Comparative study of the Chatham Islands Odonata: Morphological variability, behaviour and demography of the endemic Xanthocnemis tuanuii Rowe, 1987

Faunistic investigations on adult insects and molecular research on larvae have identified the existence of at least four species of Odonata on the Chatham Islands. The species resemble their New Zealand counterparts, although there are morphological deviations from the typical diagnostic features. Molecular evidence is not concordant with earlier morphological results as far as the genus Xanthocnemis is concerned. Genetic data suggest there are two species on the island while morphological investigations revealed just one. This topic needs further clarification and is given special attention in the present study. The main aim of the present study is to establish the taxonomic position of Chatham Island Xanthocnemis species and its relation to New Zealand main island fauna. It also provides some data on the biology of the local species and estimates of key demographic parameters (i.e., survival and abundance). The results show that Chatham Islands inhabitants are close morphologically to their New Zealand main island counterparts. Between-island differences in wing area and abdomen-to-body length ratio were found, but were largely attributable to the harsh environment on the Chatham Islands and its influence on body size. Chatham Xanthocnemis exhibited low survival rates and a great diversity of female colour morphs and certain behavioural traits (like underwater oviposition), which are suspected to be due to a composite influence of low summer temperatures, constant winds, and low pH. Ultimately, the taxonomic status of the Chatham Island Xanthocnemis species needs further confirmation based on molecular analysis of adults.