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Australian Journal of Botany Australian Journal of Botany Society
Southern hemisphere botanical ecosystems
RESEARCH ARTICLE

The comparative study of range-wide genetic structure across related, co-distributed rainforest trees reveals contrasting evolutionary histories

Maurizio Rossetto A C , Darren Crayn A , Andrew Ford B , Peter Ridgeway A and Paul Rymer A
+ Author Affiliations
- Author Affiliations

A National Herbarium of New South Wales, Botanic Gardens Trust, Mrs Macquaries Road, Sydney, NSW 2000, Australia.

B CSIRO, Sustainable Ecosystems and Rainforest-CRC, Tropical Forest Research Centre, PO Box 780, Atherton, Qld 4883, Australia.

C Corresponding author. Email: Maurizio.Rossetto@rbgsyd.nsw.gov.au

Australian Journal of Botany 55(4) 416-424 https://doi.org/10.1071/BT06195
Submitted: 21 September 2006  Accepted: 11 January 2007   Published: 20 June 2007

Abstract

Australia’s rainforests exhibit high taxonomic diversity and endemism, yet relatively little is known about patterns of genetic diversity across the flora. Habitat contractions caused by the aridification of the continent and the recent glacial cycles have left discrete genetic signatures on modern-day populations, with the nature of between-population differentiation likely to be influenced by a range of ecological and environmental factors. We used microsatellites to examine range-wide population genetic structure in two congeneric rainforest trees, Elaeocarpus angustifolius and E. largiflorens (Elaeocarpaceae), with similar habitat preference and dispersal potential. The aim was to investigate the relationships between genetic structure, geographic disjunction and morphological differentiation and attempt to clarify the likely evolutionary processes responsible for the observed patterns. We found substantial differences in the amount and type of genetic differentiation within the two co-distributed species. While Elaeocarpus largiflorens revealed an abrupt genetic disjunction front between two subspecies separated by a recognised biogeographic barrier (the Black Mountain Corridor), E. angustifolius showed lower genetic differentiation across a much wider geographic area. Our findings suggest that biogeographic features have different impacts on related species, and that generalisations on evolutionary patterns can be untenable without considering a range of factors. Also, on the basis of the available molecular data, a likely hypothesis is of pre-Pleistocene differentiation followed by reinforcement of differentiation patterns during recent glacial cycles (further studies are needed to conclusively date divergence).


Acknowledgements

The authors thank J. Hunter, B. Hewett, W. Cooper and K. Kupsch for field support. This project was funded by an Australian Research Council SPIRT grant (C00107305); the Hermon Slade Foundation (HSF 03-11); and NSW National Parks and Wildlife Service (NSW DEC). Permits to collect in WT were issued by the Environmental Protection Agency and the Queensland Parks and Wildlife Service.


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