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Australian Wet Tropics

The Australian Wet Tropics (AWT) World Heritage Area is notable for its high diversity and local endemism, harboring 75 regionally-endemic and rainforest-restricted species of vertebrate of which 13 (six microhylid frogs and seven lizards) are restricted to single upland subregions (ref). The rainforests of the AWT occur across a stable geological setting and are thought to be ancient and relictual, representing a rainforest biota that was widespread on the Australian continent in the early Miocene (Adam 1992; Morley 2000; Greenwood & Christophel in press). Seated within the northern stretches of a larger, fragmented coastal “mesotherm archipelago” (Nix 1991; 1993), east of the Great Dividing Range, the AWT is the largest surviving tract of Gondwanan rainforest (<1Mha). With the exception of microhylid frogs (Cophixalus), molecular phylogenies indicate very little speciation in situ (most sister taxa of AWT species are in rainforests elsewhere) and levels of sequence divergence are more consistent with Mio-Pliocene, than late Pleistocene divergences (Moritz et al. 2000). Palynological evidence from crater lakes and offshore drilling sites suggests that rainforests persisted (with local range adjustments between wet-angiosperm and dry-gymnosperm types) over the climatic oscillations from the Pliocene to the last glacial maximum, but contracted severely at that time, prior to expanding rapidly across upland regions during the early Holocene (Kershaw 1994; Hopkins et al. 1993; Kershaw et al., in press). Modeling of Quarternary rainforest distributions under the cool dry LGM climate indicates contraction to (mostly) montane isolates in the central (CWT) and northern (NWT) regions (Nix 1991; Graham, Williams & Moritz, in prep). The NWT and CWT refugia are separated by the Black Mountain Barrier (BMB), and the CWT and SWT by the Tully River gorge. Within the NWT modeling predicts multiple, disconnected refugia, whereas the CWT is predicted to contain larger and more continuous refugial areas. By contrast, the modeling predicts only minute, if any, refugia within the SWT. Patterns of narrow endemism for low vagility invertebrates are consistent with this hypothesis in that there are numerous single subregion endemics within the NWT and CWT, but few in the SWT (Moritz et al. 2001).

The rainforests of north-eastern Australia (AWT) are a highly appropriate system for addressing question driven research in evolutionary biology, macroecology, phylogeographic methodology, and conservation. There is a high diversity of rainforest amphibian and reptile endemics, with varying degrees of specialization to specific rainforest types and varying climatic breadth; The species taxonomy is well resolved and there are extensive spatial data on species distributions and relevant environmental variables; A combination of paleo-ecological evidence and modeling of potential distributions of rainforest vegetation under past climates show that rainforests have contracted and expanded repeatedly in response to climate fluctuations; Assemblage diversity and structure has been quantified across multiple spatial scales and in regions with different biogeographic histories; and Extensive mtDNA phylogeographic evidence demonstrates strong, but variable impacts of changes in rainforest distribution on the endemic species.




Craig Moritz Research Group - Home

Museum of Vertebrate Zoology
Department of Integrative Biology
University of California, Berkeley