Abstract
Elaborate and expensive endeavours are underway worldwide to understand and manage biological invasions. However, the success of such efforts can be jeopardised due to taxonomic uncertainty. We highlight how unresolved native range taxonomy can complicate inferences in invasion ecology using the invasive tree Acacia dealbata in South Africa as an example. Acacia dealbata is thought to comprise two subspecies based on morphological characteristics and environmental requirements within its native range in Australia: ssp. dealbata and spp. subalpina. Biological control is the most promising option for managing invasive A. dealbata populations in South Africa, but it remains unknown which genetic/taxonomic entities are present in the country. Resolving this question is crucial for selecting appropriate biological control agents and for identifying areas with the highest invasion risk. We used species distribution models (SDMs) and phylogeographic approaches to address this issue. The ability of subspecies-specific and overall species SDMs to predict occurrences in South Africa was also explored. Furthermore, as non-overlapping bioclimatic niches between the two taxonomic entities may translate into evolutionary distinctiveness, we also tested genetic distances between the entities using DNA sequencing data and network analysis. Both approaches were unable to differentiate the two putative subspecies of A. dealbata. However, the SDM approach revealed a potential niche shift in the non-native range, and DNA sequencing results suggested repeated introductions of different native provenances into South Africa. Our findings provide important information for ongoing biological control attempts and highlight the importance of resolving taxonomic uncertainties in invasion ecology.
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Acknowledgements
Funding was provided by the DST-NRF Centre of Excellence for Invasion Biology and the Working for Water Programme through their collaborative research project on “Integrated Management of invasive alien species in South Africa” and a Subcommittee B grant from Stellenbosch University (to JLR), and the Drakenstein Trust. Additional financial support was provided by the DST-NRF Centre of Excellence for Invasion Biology, Stellenbosch University, and the National Research Foundation of South Africa (Grant Nos. 85417 to DMR). We thank C. Gairifo, J. Ndlovu, and J.R.U. Wilson for collecting and/or providing samples analyzed in this study, and H. Kaplan for supplying occurrence records listed in the Southern African Plant Invaders Atlas. We are grateful to M.J. Koordom and P.H. Du Preez for assistance in the laboratory. We also thank the two anonymous referees whose suggestions helped to clarify and improve this manuscript significantly.
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Hirsch, H., Gallien, L., Impson, F.A.C. et al. Unresolved native range taxonomy complicates inferences in invasion ecology: Acacia dealbata Link as an example. Biol Invasions 19, 1715–1722 (2017). https://doi.org/10.1007/s10530-017-1381-9
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DOI: https://doi.org/10.1007/s10530-017-1381-9