Where they are, why they are there, and where they are going: using niche models to assess impacts of disturbance on the distribution of three endemic rare subtropical rainforest trees of Macadamia (Proteaceae) species

Abstract

Species within the Macadamia genus (Proteaceae) are rare and threatened narrowly distributed inhabitants of subtropical lowland rainforests of eastern Australia. Despite their strong cultural links and economic importance as a source of germplasm for the macadamia nut industry, a comprehensive assessment of factors contributing to their conservation status, or the potential impacts of climate change, is lacking. We used maximum entropy models to identify the respective niche of the following three Macadamia species with overlapping extant distributions: M. integrifolia, M. ternifolia and M. tetraphylla. We used model predictions to identify and prioritise respective areas of habitat, together with change in geographic distribution of habitats between 1990 and 2070 climates. Results reveal considerable overlap in the geographic extent of habitat among the three species; however, the extent of current occupation of habitat by any individual species is limited. Relatively high levels of clearing of ecological communities strongly associated with M. integrifolia or M. ternifolia have occurred within the extent of their respective habitats, with M. tetraphylla less affected within the Queensland extent of its range. Response to climate change varies among the three species, with a general trend of shift in respective niche to areas that currently experience relatively high precipitation and lower temperature regimes.