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Cultivation shapes genetic novelty in a globally important invader

Authors

  • GENEVIEVE D. THOMPSON,

    1. Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Matieland 7602, South Africa
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  • DIRK U. BELLSTEDT,

    1. Department of Biochemistry, Stellenbosch University, Matieland 7602, South Africa
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  • MARGARET BYRNE,

    1. Department of Environment and Conservation, Science Division Locked Bag 104, Bentley Delivery Centre, Bentley, WA 6983, Australia
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  • MELISSA A. MILLAR,

    1. Department of Environment and Conservation, Science Division Locked Bag 104, Bentley Delivery Centre, Bentley, WA 6983, Australia
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  • DAVID M. RICHARDSON,

    1. Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Matieland 7602, South Africa
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  • JOHN R.U. WILSON,

    1. Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Matieland 7602, South Africa
    2. South African National Biodiversity Institute, Kirstenbosch National Botanical Gardens, Claremont 7735, South Africa
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  • JOHANNES J. LE ROUX

    1. Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Matieland 7602, South Africa
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Johannes J. Le Roux, Fax: + 27 21 808 2995; E-mail: jleroux@sun.ac.za

Abstract

Acacia saligna is a species complex that has become invasive in a number of countries worldwide where it has caused substantial environmental and economic impacts. Understanding genetic and other factors contributing to its success may allow managers to limit future invasions of closely related species. We used three molecular markers to compare the introduced range (South Africa) to the native range (Western Australia). Nuclear markers showed that invasive populations are divergent from native populations and most closely related to a cultivated population in Western Australia. We also found incongruence between nuclear and chloroplast data that, together with the long history of cultivation of the species, suggest that introgressive hybridization (coupled with chloroplast capture) may have occurred within A. saligna. While we could not definitively prove introgression, the genetic distance between cultivated and native A. saligna populations was comparable to known interspecific divergences among other Acacia species. Therefore, cultivation, multiple large-scale introductions and possibly introgressive hybridization have rapidly given rise to the divergent genetic entity present in South Africa. This may explain the known global variation in invasiveness and inaccuracy of native bioclimatic models in predicting potential distributions.

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