Why are Australian rainforest species distributed and assembled the way they are?
Why do some species have limited distributions, and why are regions such as the Nightcap and Border Ranges in NSW and the Wet Tropics in Queensland more diverse than others?
The dispersal of fruit (and seed) by animals is a crucial component of the distribution and dynamics of plants, the structure of forests, and the maintenance of landscape-level diversity. We found that rainforest plants with small fleshy fruits (less than 3 centimeters in diameter) are generally more common and distributed more widely than species with larger fruits. This is particularly true in southern Queensland and northern New South Wales, where the number of animals capable of ingesting and dispersing larger fruits is limited.
We also found that in both the tropics and subtropics, the richness of large-fruited rainforest species tracks the distribution of environmentally stable refugia. This suggests that many rainforest areas are (or have been) too small and/or too locally dissected to retain animals capable of supporting the dispersal of species with large fruits. For example, in the subtropics many large-fruited species belonging to the family Lauraceae (the family of the avocado) and Sapotaceae are rare and highly restricted in distribution.
Since subtropical rainforests do not have animals able to disperse large-fruited species between forest remnants (such as Cassowaries in tropical rainforests), specific management strategies targeting large-fruited taxa need to be considered. Based on well-informed genetic and environmental guidelines, these include population augmentation (where individuals from different populations are mixed to increase diversity and fitness) and assisted migration (where new populations are established in suitable habitat outside their current range).
We use the latest genetic tools in combination with ecological and distributional information to understand how dispersal impacts the distribution and assembly of rainforest species.
Some of the questions that we are asking are: