XVI International Botanical Congess

Although tree diversity in New Zealand is correlated with latitude, humidity and temperature, no plausible mechanism can explain this, other than historical factors acting on regional species pools. There are striking patterns of regional endemism: areas of high endemism occur on older, more stable landscapes, and very low endemism occurs on recently uplifted areas. Besides age and stability of landscape, the extent to which an area is linked to other similar areas over the course of a glacial-interglacial cycle determines its propensity to develop and retain local endemics. Local forest endemics are uncommon, as forest covers over 90% of the landscape during an interglacial. Most local endemics tend to be plants of alpine or other non-forest habitats and uncommon soil types that have always been fragmented.