Phylogeography of the invasive Brazilian peppertree in South Africa

The Brazilian peppertree (Schinus terebinthifolia) is a problematic invasive alien plant in South Africa, originally introduced for its ornamental value from South America, and is a high priority target for biological control. Biological control, specifically the use of herbivorous insects and their larvae, has been implemented in the states of Florida and Hawaii in the USA, where S. terebinthifolia is also an invasive alien plant. Previous phylogeographic work determined that there have been multiple introductions of two lineages of the species (herein referred to as haplotypes A and B) into the USA. Haplotype A was introduced to western Florida and Hawaii, while haplotype B was introduced to eastern Florida. Haplotypes A and B have subsequently hybridised in Florida, resulting in novel plant genotypes. Biological control agents in the USA are known to vary in efficacy on the two different haplotypes and hybrids. Biocontrol agents often have greater performance on target plants that they share an evolutionary history with so a better understanding of the phylogeographic origins of South African populations could help to inform biocontrol strategies.

In their new study published in AoBP, Canavan et al. used molecular techniques to uncover the source populations of S. terebinthifolia in South Africa using chloroplast DNA and microsatellites. Populations from the introduced ranges in Florida (east, west and hybrids) and Hawaii were also included in the analysis. Comparing this phylogeographic data to previous work on the efficacy of biocontrol agents in Florida and Hawaii will help to inform which will be most suitable for use in South Africa.

In their analysis, Canavan et al. found that only one haplotype was present in the 51 South African samples. Microsatellite analysis determined shared alleles with haplotype A from western Florida and Hawaiian populations. The likely source of South African S. terebinthifolia was, however, determined to be western Florida via horticultural trade. The results of this work will help guide a biocontrol programme to source agents that perform well on the same haplotype in the USA. Early indications suggest that the thrip biocontrol agent Pseudophilothrips ichini from the Ouro Preto population would be best suited for South Africa as they have been shown to perform well in controlling haplotype A in Florida. In addition to the already established agents in Hawaii and Florida, there are a number of potential biocontrol agents that are likely to be released in the near future, including the stem boring weevil, that could be considered for use in South Africa.

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Canavan, K., Magengelele, N.L., Paterson, I.D., Williams, D.A. and Martin, G.D. (2022) “Uncovering the phylogeography of Schinus terebinthifolia in South Africa to guide biological control,” AoB plants, 14(1), https://doi.org/10.1093/aobpla/plab078