WILDLIFE OF LANCEWOOD (ACACIA-SHIRLEYI) THICKETS AND WOODLANDS IN NORTHERN AUSTRALIA .2. COMPARISONS WITH OTHER ENVIRONMENTS OF THE REGION (ACACIA WOODLANDS, EUCALYPTUS SAVANNA WOODLANDS AND MONSOON RAIN-FORESTS)

Embedded in the extensive Eucalyptus open forests and savanna woodland s that dominate the northern Australian landscape are patches of monso on rainforest and Acacia thickets and woodlands. In this paper, the ve rtebrate species composition of patches of lancewood (Acacia shirleyi) thickets and woodlands of the Northern Territory is compared with tha t of other environments of this region: two other Acacia woodlands (pi ndan and gidgee), patches of monsoon rainforests and the extensive Euc alyptus open forests and woodlands. The vertebrate fauna of lancewood thickets is distinct from that of Eucalyptus open forests, and has few er species. Differences in species composition and richness are associ ated with substantial differences in resource availability, with lance wood thickets having far less grass cover (and hence relatively few gr anivorous birds and rodents, but more ground-feeding insectivorous and omnivorous birds), fewer nectar-bearing flowers (and hence fewer nect arivorous birds) and lower structural and floristic diversity than Euc alyptus open forests. There is little difference in species richness o r total abundance between the three types of Acacia woodlands sampled. Lancewood thickets have fewer species than monsoon rainforests. Speci es composition Varies almost continuously from coastal wet monsoon rai nforests to coastal dry monsoon rainforests to inland dry monsoon rain forests to lancewood thickets to pindan woodlands to gidgee woodlands, in accord with the pronounced rainfall gradient of this region and wi th canopy cover and height. Within this broad continuum the three Acac ia woodlands are most closely grouped. Species turnover along this gra dient consists of substantial decrease or loss of some foraging groups (e.g. frugivorous birds) or replacement of species within broad forag ing groups. The faunal relationship of the monsoon rainforests and Aca cia communities provides some support for considering these fire-sensi tive environments as fragments of a formerly extensive continuum. Thre e species (Pomatostomus temporalis, Struthidea cinerea and Melanodryas cucullata), all ground-foraging insectivorous or omnivorous birds, we re significantly associated with lancewood in this region, but all thr ee have extensive ranges beyond this area.