Acacia saligna, the Port Jackson willow, is considered to be one of the most costly invasive plants in South Africa as it transforms ecosystems and alters nutrient cycles and fire regimes across the several million hectares of land it invades in the Western Cape. This woody invader also occurs in more than 20 countries, but is only considered invasive in six of these countries, the reason for which is unknown.

C·I·B Ph.D. student, Genevieve Thompson employed population genetic and phylogenetic methods to study this species in South Africa and abroad. Genevieve and her co-authors (including C·I·B core team members Dave Richardson, John Wilson and Jaco Le Roux), showed that the South African invasion is genetically novel compared with the native lineages present in Western Australia. Surprisingly, this genetic novelty is unparalleled in other introduced populations sampled in Israel, Italy, Portugal, Spain and the USA, and may be the cause of the successful invasion of the species in South Africa. The genetic novelty of South African populations is thought to be due to the long history of cultivation of Acacia saligna in its native range, and the manner and scale at which the species was introduced and planted in South Africa. This work earned Genevieve the award for ‘Best Presentation by a Ph.D. Student’ at the South African Association of Botanists (SAAB) conference in Pretoria in January, and has more recently been published in Molecular Ecology.

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Read the paper: Thompson, G.D., Bellstedt, D.U., Byrne, M., Millar, M.A., Richardson, D.M., Wilson, J.R.U., Le Roux, J.J. (2012) Cultivation shapes genetic novelty in a globally important invader. Molecular Ecology, 21, 3187-3199.

For further details, contact Genevieve Thompson at gen@sun.ac.za