Speciation in the Australian flora: testing explanatory hypotheses in waratahs and their allies

A project undertaken at the National Herbarium of New South Wales, Botanic Gardens and Domain Trust, and supervised by Dr Maurizio Rossetto and Dr Peter Weston

What came first: clades or the barriers that separate them; adaptation to local conditions or dispersal into new habitat? Does morphological variation reflect intra-specific or inter-specific patterns?  To explore these and other evolutionary questions, we propose to investigate the population biology, phylogeography, phylogeny and historical biogeography of Telopea and Lomatia (Proteaceae) in south eastern Australia. By extending our earlier morphology-based studies to the population level using newly developed molecular markers, we will investigate evolutionary patterns and establish a framework for further in-depth studies on the unique Australian flora. The aims of this project are to test the following null hypotheses: vicariant allopatric speciation has prevailed throughout the evolution of both Telopea and Lomatia; hybridization and convergent evolution in similar habitats have not been significant processes in the evolution of these taxa. We suspect that this model is overly simplistic, but believe that novel insights will emerge by asking these questions of this group of plants. This research will provide one of the few detailed examinations of the processes of speciation in the Australian flora, focusing on a family that has been a characteristic element of the flora since Gondwanan fragmentation.

Our aim is to obtain a better understanding of evolutionary processes in the Australian flora by investigating selected sister groups within the Proteaceae. These groups were selected because relevant background knowledge and techniques are available from our previous research, and because their distribution and diversification patterns are relevant to the evolutionary questions we are posing. To achieve our scientific aims and make sufficient progress to encourage future, more extensive evolutionary projects, we will follow a three-phased approach:

  1. We will first reconstruct the phylogeny and evolutionary time-scale for the clades of interest using new molecular data and the existing fossil record. This preliminary knowledge is essential for comparative studies on phylogenetic radiation.
  2. We will then obtain novel comparative phylogeographic data across the sub-tribes of interest to identify the relative historical influence of environmental and geographic features on phylogenetic differentiation.
  3. Finally we will use fine-scale population data to measure current gene-flow levels across selected sister species pairs. This will enable us to follow more closely the genetic, ecological and environmental factors favouring or preventing differentiation.
References

Rossetto, M, Thurlby, KAG, Offord, CA, Allen, CB and Weston, PH: (2011). The impact of distance and a shifting temperature gradient on genetic connectivity across a heterogeneous landscape. BMC Evolutionary Biology, 11: 126 - 137.

Rossetto, M, Allen, CB, Thurlby, KAG, Weston, PH and Milner, ML: (2012). Genetic structure and bio-climatic modeling support allopatric over parapatric speciation along a latitudinal gradient. BMC Evolutionary Biology, 12: 149

Milner, ML, Rossetto, M, Crisp, MD and Weston, PH: (2012). The impact of multiple biogeographic barriers and hybridization on species-level differentiation. American Journal of Botany, 99: 2045-2057.

 

Figure 1. Telopea truncata inflorescences Cradle Mountain Lodge (photo Peter Weston)

Figure 2. Lomatia fraxinifolia flowers (photo Jaime Plaza)

Figure 3. Lomatia fraxinifolia follicle with seeds (photo Peter Weston)

Figure 4. Lomatia silaifolia (Photo Peter Weston)

Figure 5. Telopea mongaensis Gunrock Ck inflorescences (photo Peter Weston)

Figure 6. Telopea speciosissima (photo Peter Weston)