Does the diversity of plant function strategies found in different communities reflect prevailing environmental limitations? By surveying three types of Australian rainforest, all of which are derived from a common ancestral flora, we test whether the greatest diversity in a range of traits occurs in response to the most important limiting conditions in each environment. We have chosen to explore this question in Australian rainforests because they occur in three different seasonality regimes: (1) warm-and-wet tropical rainforest; (2) seasonally tropical dry rainforest; (3) seasonally cold temperate rainforest. Our study includes several different functional traits which are well-correlated with complex aspects of plant survival strategies, such as drought response, cold tolerance, growth strategy, competitive ability, and response to disturbance. These traits have been sampled across a wide range of taxa at each site, and analyzed in both traditional statistical and phylogenetic community contexts.

Results/Conclusions

Our study shows that as Australian wet tropical forests radiated into dry and cold environments, plants within each community followed different paths to cope with the stresses in these environments. We observed the greatest variance of traits related to drought tolerance in the tropical dry forest community, and the greatest diversity of traits related to cold tolerance in the cool temperate rainforest. Both seasonal environments showed greater variance in traits related to leaf lifespan than the wet tropical forest, partly due to convergence on either evergreen or deciduous habits in these environments. We tested for evidence that competition is a limiting condition in the wet tropical forest, but were not able to support this hypothesis. The implications of these findings for global change, including aridification of regions which currently support wet tropical rainforest, are discussed.