What factors control the distribution and abundance of folivorous possums inhabiting rainforests of the Atherton Tablelands, in north-east Queensland?

Abstract

Four species of folivorous possums inhabit rainforests of the Atherton Tablelands, north Queensland, including the lemuroid (Hemibelideus lemuroides), green (Pseudochirops archeri) and Herbert River ringtail possums (Pseudochirulus herbertensis), and the coppery brushtail possum (Trichosurus vulpecula johnstoni). All four possums display a striking response to altitude, being more abundant in highland (> 800 m) than upland (400 - 800 m) forests. Additionally, three of the four possums (H. lemuroides, P. herbertensis and T.v. johnsoni) are more abundant in forests on nutrient-rich basalt soils than forests on nutrient-poor acid igneous and metamorphic soils. Variation in the abundance of the possums with geology appears to be a response to foliar chemistry. However, altitudinal variation in possum abundance is not related to foliar chemistry, nor to the floristic composition of forests, the distribution of the rufous owl (a predator of the possums), or the availability of dens. It is argued that the 'climate hypothesis' offers the most plausible explanation for the restriction of the possums to higher elevation forests in the region. If correct, then the possums may be vulnerable to climate change. Global warming would be expected to greatly reduce the distributions of possums, while the projected increase in atmospheric concentrations of carbon dioxide may lower the nutritional quality of foliage, further reducing the abundance of the possums within their ranges.