Abstract
AbstractAimTo compare genetic diversity and structure between Acacia dealbata populations sampled across the species’ native range in Australia and from its non‐native ranges in Chile, Madagascar, New Zealand, Portugal, La Réunion island, South Africa and the United States, and to investigate the most likely introduction scenarios to non‐native ranges.LocationGlobal.TaxonAcacia dealbata, Fabaceae.MethodsOur dataset comprised 1615 samples representing 92 populations sampled in the species’ native and non‐native ranges. We employed a combination of genetic fingerprinting (microsatellite markers) and genetic modelling approaches. We calculated genetic diversity for each population and tested for genetic isolation by distance within each range. A combination of Bayesian assignment tests and multivariate ordination was applied to identify genetic structure among populations. Approximate Bayesian Computation (ABC) analyses were conducted to test different competing introduction scenarios for each non‐native range.ResultsThe majority of the species’ non‐native ranges was characterized by high genetic diversity and low levels of genetic structure. With regard to introduction histories, however, our results supported different introduction scenarios for different non‐native ranges. We did not find strong support for any of tested introduction scenarios for populations in Chile and Madagascar, but these likely originated from multiple introductions followed by admixture. Populations in New Zealand and La Réunion most likely originated directly from Tasmania, possibly through multiple introductions. Similar to previous findings for South African populations, no clear introduction history could be identified for populations in Portugal and the United States.Main conclusionsOur study shows that global introductions of A. dealbata were complex and one scenario does not fit the invasion history of the species in different regions. We discuss how this complexity needs to be considered when formulating strategies for the effective management of the species. Future research needs to help bridge persisting knowledge gaps are discussed.
Highlights
Invasive species are a major threat to biodiversity and human livelihoods, and recent estimates show that one-sixth of the world's land surface is highly vulnerable to invasion (Early et al, 2016)
This study focuses on Acacia dealbata Link and, the reconstruction of the history of human-mediated movement of this species around the globe
To gain a more comprehensive understanding of the species' introduction history around the world, this study aims to compare the two native lineages of A. dealbata with invasive populations from Chile, Madagascar, New Zealand, Portugal, La Réunion and the United States—countries that represent some of the species most prominent invasive ranges (Lorenzo et al, 2010; Richardson et al, 2011)
Summary
Invasive species are a major threat to biodiversity and human livelihoods, and recent estimates show that one-sixth of the world's land surface is highly vulnerable to invasion (Early et al, 2016). Features commonly related to the invasiveness of acacias include their ability to form symbiosis with nitrogen-fixing bacteria, allelopathy, fast growth, ability to re-sprout after cutting, massive seed production, long seed viability and high intraspecific variability (Gibson et al, 2011; Le Roux et al, 2011; Morris et al, 2011; Souza-Alonso et al, 2017; Yannelli et al, 2020). These and other factors, such as the commercial value and extensive planting of acacias, can greatly complicate the management of invasive populations.
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