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Phylogenetic placement and the timing of diversification in Australia's endemic Vachellia (Caesalpinioideae, Mimosoid Clade, Fabaceae) species

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Comben, D. F., McCulloch, G.A., Brown, G.K. and Walter, G.H. (2020) Phylogenetic placement and the timing of diversification in Australia's endemic Vachellia (Caesalpinioideae, Mimosoid Clade, Fabaceae) species. Australian Systematic Botany, 33 (1). pp. 103-109. ISSN 10301887 (ISSN)

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Article Link: https://doi.org/10.1071/SB19013


The genus Vachellia Wight & Arn. has a pantropical distribution, with species being distributed through Africa, the Americas, Asia and Australia. The relationships among the lineages from Africa and America are well understood, but the phylogenetic placement and evolutionary origins of the Australian species of Vachellia are not known. We, therefore, sequenced four plastid genes from representatives of each of the nine Australian species of Vachellia, and used Bayesian inference to assess the phylogenetic placement of these lineages, and a relaxed molecular clock to assess the timing of diversification. The Australian species of Vachellia form a well-supported monophyletic clade, with molecular-dating analysis suggesting a single dispersal into Australia 6.5 million years ago (95% range 13.9-2.7 million years ago). Diversification of the Australian clade commenced more recently, c. 3.1 million years ago (95% range 9.2-1.2 million years ago), perhaps driven by the increased aridification of Australia at this time. The closest relatives to the Australian Vachellia were not from the Malesian bioregion, suggesting either a long-distance dispersal from Africa, or two separate migrations through Asia. These results not only improve our understanding of the biogeography of Vachellia species, but also have significant implications for the biological control of invasive Vachellia species in Australia. © 2020 CSIRO.

Item Type:Article
Corporate Creators:Department of Agriculture and Fisheries, Queensland
Business groups:Biosecurity Queensland
Keywords:biogeography biological control dispersal ecoregion endemic species legume phylogenetics Africa Asia Australia Central America North America South America Acacia Caesalpinioideae Fabaceae
Subjects:Science > Invasive Species > Plants > Biological control
Plant pests and diseases > Weeds, parasitic plants etc
Agriculture > By region or country > Australia
Live Archive:01 May 2024 05:30
Last Modified:01 May 2024 05:30

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