Abstract
Here we investigate the interaction between ecology and climate concerning the distribution of rainforest species differentially distributed along altitudinal gradients of eastern Australia. The potential distributions of the two species closely associated with different rainforest types were modelled to infer the potential contribution of post-glacial warming on spatial distribution and altitudinal range shift. Nothofagus moorei is an integral element of cool temperate rainforest, including cloud forests at high elevation. This distinct climatic envelope is at increased risk with future global warming. Elaeocarpus grandis on the other hand is a lowland species and typical element of subtropical rainforest occupying a climatic envelope that may shift upwards into areas currently occupied by N. moorei. Climate envelope models were used to infer range shift differences between the two species in the past (21 thousand years ago), current and future (2050) scenarios, and to provide a framework to explain observed genetic diversity/structure of both species. The models suggest continuing contraction of the highland cool temperate climatic envelope and expansion of the lowland warm subtropical envelope, with both showing a core average increase in elevation in response to post-glacial warming. Spatial and altitudinal overlap between the species climatic envelopes was at a maximum during the last glacial maximum and is predicted to be a minimum at 2050.
Highlights
The far-eastern rainforests of Australia occur at the junction between the temperate and tropical climatic regions (32–25°S), and the area is a World Heritage listed biodiversity hotspot (i.e., CentralEastern Rainforest Reserves of Australia)
Analysis of variable contribution indicated that for the cool temperate Nothofagus moorei: precipitation of the warmest quarter explained 24%, precipitation of the driest quarter explained 21%, mean temperature of the warmest quarter explained 7% and maximum temperature of the driest month explained 7% of the current distribution
Analysis of variable contribution indicated that for E. grandis: annual precipitation explained 35%, mean temperature of the coldest quarter explained 27%, precipitation of the wettest quarter 10% and precipitation of the warmest quarter 8% of the current distribution
Summary
The far-eastern rainforests of Australia occur at the junction between the temperate and tropical climatic regions (32–25°S), and the area is a World Heritage listed biodiversity hotspot (i.e., CentralEastern Rainforest Reserves of Australia). It is generally assumed that distributional differences in rainforest communities are primarily a result of altitude and other abiotic gradients [2,3] Within this zone of climatic overlap, subtropical genera are found in the moister habitats of the wet gullies of the eastern slopes of the ranges and on the coastal lowlands, while temperate genera form more open habitats on higher slopes where temperatures fall below those suitable for tropical species [4]. These rainforests show altitudinal changes in floristic community structure along the latitudinal gradient of the Great Dividing Range (GDR) of eastern Australia (e.g., some highland rainforest elements in the warmer north, occupy lowland areas in the cooler south [5]). A rainforest species’ dispersal ability [7,8,9] is important in explaining the difference between its potential and observed distribution
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