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R Soc Open Sci. 2017 Apr 12;4(4):170105. doi: 10.1098/rsos.170105. eCollection 2017 Apr.

Chance long-distance or human-mediated dispersal? How Acacia s.l. farnesiana attained its pan-tropical distribution.

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Royal Botanic Gardens Victoria, Melbourne, Victoria 3004, Australia.
Australia India Institute and School of Geography, University of Melbourne, Victoria 3053, Australia.
Monash Indigenous Centre, Monash University, Victoria 3800, Australia.
Centro de Estudos de Geografia e Ordenamento Território, Universidade do Porto, Portugal.
Institut de Géographie et Durabilité, Université de Lausanne, Lausanne 1015, Switzerland.


Acacia s.l. farnesiana, which originates from Mesoamerica, is the most widely distributed Acacia s.l. species across the tropics. It is assumed that the plant was transferred across the Atlantic to southern Europe by Spanish explorers, and then spread across the Old World tropics through a combination of chance long-distance and human-mediated dispersal. Our study uses genetic analysis and information from historical sources to test the relative roles of chance and human-mediated dispersal in its distribution. The results confirm the Mesoamerican origins of the plant and show three patterns of human-mediated dispersal. Samples from Spain showed greater genetic diversity than those from other Old World tropics, suggesting more instances of transatlantic introductions from the Americas to that country than to other parts of Africa and Asia. Individuals from the Philippines matched a population from South Central Mexico and were likely to have been direct, trans-Pacific introductions. Australian samples were genetically unique, indicating that the arrival of the species in the continent was independent of these European colonial activities. This suggests the possibility of pre-European human-mediated dispersal across the Pacific Ocean. These significant findings raise new questions for biogeographic studies that assume chance or transoceanic dispersal for disjunct plant distributions.


Acacia farnesiana; Vachellia farnesiana; cryptogenic species; human-mediated dispersal; pan-tropical species; transoceanic dispersal

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