What are the main processes impacting on the diversification of the Australian flora (drift, hybridization, and population expansion/contraction events for example)? Can we identify temporal patterns driving diversification events, and can we relate these to historical environmental circumstances? What is a species, and how do its boundaries change through time and space.
We use a range of phylogenetic and population-level analytical approaches to explore the evolution of the Australian flora. Specific projects include phylogenetic studies aimed at exploring the timing of diversification within Australian rainforest lineages. These include Lauraceae, Elaeocarpaceae and Cunoniaceae. Our work indicates that many of these lineages are relatively young and that speciation is likely to have occurred following landscape-level fragmentation by aridification processes.
Phylogenetic and population studies of the flora of the Sydney region across Eucalyptus (the green ash group for example, Myrtaceae), Telopea and Lomatia (Proteaceae) suggest that frequent admixture between differentiated populations and species is an important evolutionary mechanism within this highly diverse flora.
A collaborative project is using a whole-chloroplast phylogeny of 76 Australian rainforest species covering the breadth of the angiosperm phylogeny to investigate important timings in diversification across several taxonomic groups. Estimates obtained from the multifamily chronogram will be applied to explore several population-level questions, such as the investigation of the timing of the landscape-level processes that defined the current distribution of Australian rainforests.
Population level studies indicate that biogeographical barriers have had an impact on several phylogenetically independent species, although patterns of population expansion differ even amongst close relatives. Post-differentiation admixture (hybridization) plays and important role in maintaining diversity and might even play a role in adaptive resilience.