Movement of plants into pre-British Australia

Project summary

This project is part of an ARC Discovery project, in collaboration with the Department of Geography and Environmental Science at Monash University. The aim of this project is to determine the timing and pathway of the arrival ofAcacia (s.l.) farnesiana (Mimosa Bush) and Adansonia gregorii (Australian Baobab, or Boab) into Australia.

The project is utilising evidence from two diverse fields of research. Researchers at the Royal Botanic Gardens (RBG) Melbourne are comparing the genetics of the plant species across their entire range. Because plants from geographic localities with a more recent connection are more similar genetically, this information allows us to estimate the pathway and timing of dispersal to Australia. Researchers at Monash University are gathering historical data on human-mediated dispersal, from both colonial and indigenous sources.

Acacia (s.l.) farnesiana likely originated in Central America, but now has a pan-tropical distribution. The timing of its arrival in Australia, and hence its status as native or alien, remains unknown. It is thought to have been brought to Europe in the seventeenth century on Spanish or Portuguese ships. Spain and Portugal both had a strong colonial presence in the Indian Ocean at this time, through which further dispersal of the plant was possible. However, it is unknown to what extent A. farnesiana had dispersed throughout the global tropics prior to colonial times. Natural ocean currents and indigenous traders may have played a role in earlier dispersal. At RBG Melbourne, we are using genetic data to determine whether the dispersal of this plant to populations outside the Americas occurred before or after European settlement – or even human settlement – of the Americas.

Adansonia gregorii has a narrow distribution in the Kimberley region of Western Australia. It is a member of a genus that also includes six species in Madagascar and one species in Africa. This disjunct distribution is unusual, and is likely the result of long-distance dispersal of an ancestral species from Madagascar or Africa to Australia. This dispersal may have occurred naturally via ocean dispersal of its large, hard-cased fruit, or may have been assisted by very early human migrations out of Africa. At RBG Melbourne, we are examining the genetic diversity both within A. gregorii, and between A. gregoriiand other Adansonia species, to investigate the arrival time of this species in Australia, and whether its most recent ancestor was from Africa or Madagascar.

The research on these two species will not only improve our understanding of the evolution of the Australian flora, but will also test hypotheses of early human migrations in the region, and the role that these migrations may have played in plant evolution. This research may also have implications for defining species as native or alien, which in turn will have implications for land management.

Project team

  • Daniel Murphy (Royal Botanic Gardens Melbourne)
  • Haripriya Rangan (Monash University)
  • Christian Kull (Monash University)
  • Karen Bell (Royal Botanic Gardens Melbourne)
  • Thomas Bach (Monash University)
  • Rachael Fowler (Royal Botanic Gardens Melbourne)

Support

  • ARC Discovery Grant

Publications

Bell, K.L., Murphy, D.J. and Gardner, M.G. (2013). Isolation, via 454 Sequencing, and characterization of microsatellites for Vachellia farnesiana (Fabaceae: Mimosoideae). Applications in Plant Sciences 1(10): 1300035. doi:http://dx.doi.org/10.3732/apps.1300035

Miller, J.T., Murphy, D.J., Brown, G.K., Richardson, D.M. and González-Orozco, C.E. (2011). The evolution and phylogenetic placement of invasive Australian Acacia species. Diversity and Distributions 17(5), 848–860.

Wilson, J.R.U., Gairifo, C., Gibson, M.R., Arianoutsou, M., Bakar, B.B., Baret, S., Celesti-Grapow, L., DiTomaso, J.M., Dufour-Dror, J.-M., Kueffer, C., Kull, C.A., Hoffmann, J.H., Impson, F.A.C., Loope, L.L., Marchante, E., Marchante, H., Moore, J.L., Murphy, D.J., Tassin, J., Witt, A., Zenni, R.D. and Richardson, D.M. (2011) Risk assessment, eradication, and biological control: global efforts to limit Australian acacia invasions. Diversity and Distributions 17(5), 1030–1046.