Botanic Gardens Trust, Sydney, Australia

Rainforest diversity

Rethinking patterns of continental rainforest diversity

Dr Robert Kooyman, Dr Maurizio Rossetto, Dr Herve Sauquet, Laboratoire Ecologie, Systématique, Evolution, Université Paris-Sud, France and Dr Shawn Laffan, School of Biological, Environmental and Earth Sciences, University of New South Wales

Project outline

Using measures for phylogenetic and functional (ecological traits) variation Australia-wide, allows us to investigate the drivers of historical changes in rainforest connectivity and assembly.

Methods

We use Australia’s Virtual Herbarium distribution records of all known rainforest woody species across their full continental extent. To identify and interpret the geographical distribution of rainforest species and their evolutionary history we use population genetics and measures of species richness, phylogenetic diversity (PD), phylogenetic endemism (PE), phylogenetic structure (net relatedness index; NRI), and functional traits across continental, regional, and local scales.

Summary of results

So far we have found that species richness decreased along two generally orthogonal continental axes, representing wet to seasonally dry and tropical to temperate habitats. The PE analyses have identified four main areas of significantly restricted phylogenetic diversity. The NRI results over continental and regional scales across the full depth of the phylogeny show that generally, assemblages include species less related than expected by chance. This is particularly noticeable in larger coastally aligned areas of species rich tropical and sub-tropical rainforest, as well as low diversity cool moist forest areas south-east of the Great Dividing Range and in Tasmania. In contrast across monsoonal and drier vine forests, local assemblage tend to be represented by species that are more closely related tht expected by chance (phylo-genetic clustering). For climbing plants, values for NRI by grid cell show strong spatial structuring, with high diversity and PE concentrated in moist tropical and subtropicalregions,highlighting contrasting evolutionary, functional and assemblage histories from free-standing trees.

Main conclusions

Concentrations of rainforest evolutionary history (phylo-diversity) are patchily distributed within a continuum of species distributions. The emerging idea of continuous distributions and continental scale connectivity has significant implications for interpreting evolutionary history as well as current day ecological processes.Updating the Australian rainforest narrative using functional and phylogenetic methods will improve strategies for management of rainforest diversity in changing circumstances.

 

 

 

 

Distribution-maps

The black and white map depicts the distribution of rainforest trees and vines across the Australian continent and the major floristic regions recognised in this study. The coloured map depicts the distribution of Phylogenetic Endemism (PE), with the darker colouration identifying highest concentration of endemic trees and vines.