A preliminary survey of altitudinal variation in two ground wētā species, Hemiandrus maculifrons (Walker) and Hemiandrus pallitarsis (Walker) (Orthoptera: Anostostomatidae)

Abstract

Species’ ranges along altitudinal clines are probably influenced by their ability to adapt to a range of abiotic factors. Physical adaptations in response to lower temperatures at higher altitudes often include changes in body size. We investigated the distribution and potential change in body size with altitude of two species of ground wētā, Hemiandrus maculifrons and Hemiandrus pallitarsis in the Moehau Ecological Area on the Coromandel Peninsula, North Island, New Zealand. Over eight nights of searching, 17 adult H. maculifrons and 28 adult H. pallitarsis were found. Hemiandrus maculifrons was the smaller of the two species and was found at higher altitudes compared with H. pallitarsis (91–577 m and 27–207 m, respectively). No ground wētā were caught in baited and unbaited live-catch pitfall traps (40 set at 211–242 m above sea level; 40 at 620–626 m above sea level). Despite what appeared to be a tendency for the size of male H. maculifrons to increase with altitude, we found no evidence of intraspecific variation in body size with altitude although sample sizes were small. Nevertheless, these two species of ground wētā appear well suited to further investigations into aspects associated with factors that influence body size, distributional range shifts and climate change.