Wildlife of Lancewood (Acacia Shirleyi) Thickets and Woodlands in Northern Australia. 1. Variation in Vertebrate Species Composition Across the Environmental Range Occupied by Lancewood Vegetation in the Northern Territory.

Abstract

Vegetation dominated by lancewood (Acacia shirleyi) occurs extensively across the Northern Territory and Queensland. The vertebrate species (birds, mammals, reptiles and frogs) composition was sampled at 61 patches of lancewood in the Northern Territory (including 22 patches where quadrats were intensively sampled), and the distribution of species was related to a wide range of environmental characteristics, spatial variables, disturbance and season. Of 165 species recorded from lancewood patches, eight species were recorded from more than half of the sampled patches: Pachycephala rufiventris, Pomatostomus temporalis, Rhipidura leucophrys, Cracticus nigrogularis, Melanodryas cucullata, Geopelia cuneata, G. placida and Macropus robustus. Environmental variation within sampled lancewood sites was described by classification of 51 quadrats into 7 classes, and the 61 patches into 5 classes. Vertebrate species showed limited association with this classification, with a few species associated with the occasional co-dominant tall shrub Macropteranthes kekwickii, other species associated with variation in rockiness or soil texture, and other species associated with variation in the occurrence of Eucalyptus species within lancewood vegetation. An ordination of all quadrats by their vertebrate species composition suggested a loose patterning associated mainly with latitude and, less strongly, soil texture and co-occurring tree/shrub species (notably Eucalyptus and Macropteranthes). Suggesting a depauperate and poorly defined vertebrate community in lancewood, quadrats in small isolated lancewood patches had more species than those in large patches, and this pattern was shown for many individual species. Lancewood patches showed some impact of grazing and logging, but this was generally minor and could not be demonstrated to have any consistent relationship with the abundance of individual species. In contrast, effects of fire were generally more severe, and were negatively associated with the abundance of relatively many species. Lancewood vegetation is not represented in any conservation reserve in the Northern Territory.