Suchergebnisse

It is generally recognised that the distribution of vertebrates in rainforest
and wet sclerophyll forest of the Wet Tropics region of north-eastern
Australia is profoundly influenced by the formation of two rainforest refugia
at the height of Pleistocene glacial periods. Anomalies in the distribution of
non-volant mammals indicate that other events may be equally important. In
this paper, past geographical occurrence of non-volant mammals is examined by
equating the mammals' known temperature tolerance with palaeoclimatic
temperature zones. It is hypothesised that dispersal and vicariant phases
taking place since the most recent glacial period have had a profound
influence on current patterns of distribution. A major dispersal phase of
cool-adapted species occurred after the glacial period, and continuous
populations were subsequently fragmented into upland isolates by expansion of
warm rainforest during the late post-glacial period. These upland isolates
remain substantially unchanged to the present day. Species shared either with
New Guinea or south-eastern Australia arrived in the region during the most
recent post-glacial period. Clarification of periods of vicariance and
dispersal provides a conceptual framework for testing relative divergences of
populations within and between regions.

The ecological factors controlling the distribution and abundance of the
folivorous marsupials endemic to the rainforests of northern Australia are not
understood. In this study, we surveyed folivore abundance at 40 sites
stratified by altitude and geology in rainforests of the Atherton Tableland,
north Queensland. All five species of folivore that inhabit the study area
were more abundant in highland (800–1200 m) than in upland
(400–800 m) forests. Allowing for the effects of altitude, four species
of folivore were more abundant in forests on nutrient-rich basalts than in
forests on nutrient-poor acid igneous or metamorphic rocks. The abundance of
two folivore species also varied inversely with rainfall. Altitudinal
variation in folivore abundance in the study area has been attributed to
habitat destruction, Aboriginal hunting, the distribution of host plants and
climate; however, none of these hypotheses has been tested. Variation in
folivore abundance with geology is plausibly explained as a response to the
nutritional quality of foliage. Foliage quality may also explain the inverse
relationship between two of the folivores and rainfall. The results of this
study show that only a relatively small proportion of north Queensland
rainforests support abundant populations of the endemic folivorous marsupials.