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

Genetic diversity and biogeography of the boab Adansonia gregorii (Malvaceae: Bombacoideae)

Karen L. Bell A B E , Haripriya Rangan B , Rachael Fowler A B , Christian A. Kull B , J. D. Pettigrew C , Claudia E. Vickers D and Daniel J. Murphy A

A Royal Botanic Gardens Melbourne, Birdwood Avenue, South Yarra, Vic. 3141, Australia.

B School of Geography and Environmental Science, Monash University, Clayton, Vic. 3800, Australia.

C Queensland Brain Institute, University of Queensland, St Lucia, Qld 4072, Australia.

D Australian Institute for Bioengineering and Nanotechnology, University of Queensland, St Lucia, Qld 4072, Australia.

E Corresponding author. Email: karen.bell@monash.edu

Australian Journal of Botany 62(2) 164-174 http://dx.doi.org/10.1071/BT13209
Submitted: 23 August 2013  Accepted: 12 April 2014   Published: 22 May 2014

Abstract

The Kimberley region of Western Australia is recognised for its high biodiversity and many endemic species, including the charismatic boab tree, Adansonia gregorii F.Muell. (Malvaceae: Bombacoideae). In order to assess the effects of biogeographic barriers on A. gregorii, we examined the genetic diversity and population structure of the tree species across its range in the Kimberley and adjacent areas to the east. Genetic variation at six microsatellite loci in 220 individuals from the entire species range was examined. Five weakly divergent populations, separated by west–east and coast–inland divides, were distinguished using spatial principal components analysis. However, the predominant pattern was low geographic structure and high gene flow. Coalescent analysis detected a population bottleneck and significant gene flow across these inferred biogeographic divides. Climate cycles and coastline changes following the last glacial maximum are implicated in decreases in ancient A. gregorii population size. Of all the potential gene flow vectors, various macropod species and humans are the most likely.

Additional keywords: Australian monsoon tropics, baobab, dispersal, gene flow, genetic admixture, Kimberley, microsatellite, phylogeography.


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