On the distribution of tree weta in the North Island, New Zealand

Abstract

The distribution in the North Island of three species of tree weta (Hemideina thoracica, H. crassidens and H. trewicki) is described from field surveys. The two most widespread species (H. thoracica and H. crassidens) were generally parapatric but the boundary between the two was rather complex with a number of disjunctions. Most notable were the relict populations of H. crassidens isolated on Mt Ruapehu (39°17'S) and Mt Taranaki (39°17'S). The main boundary between these two species crosses the North Island at approximately 40° 20’ S. A recently described species (H. trewicki), found only in the Hawkes Bay region, is sympatric with H. thoracica over much of its range. These weta probably developed into separate species after they became isolated by geophysical processes, and their subsequent distribution has been the result of recent climate‐related dispersal.