Genomics reveals two distinct invasive lineages of Pereskia aculeata Miller in Australia: Implications for biological control

• Pereskia aculeata is an emerging environmental weed in Australia. • We used ddRADseq to test genetic structure across its native and introduced ranges. • Australian plants were not genetically similar to any native range samples. • We found two distinct lineages in Australia, consistent with multiple introductions. • Each lineage should be treated independently during host-range testing. Understanding the invasion history of weeds can assist practitioners in making informed decisions about weed management. This information often plays a vital role in the selection of potential biological control (biocontrol) agents from the native range and for anticipating their post-release impacts. In this study, we assessed the genetic structure of leaf cactus, Pereskia aculeata Mill. (Cactaceae), an emerging environmental weed in New South Wales and Queensland in Australia. Using a genotyping-by-sequencing (ddRADseq) approach we assessed the population structure of P. aculeata across its native range (South America) and introduced ranges in Australia and South Africa. South African plants were very closely related to plants from Argentina and Brazil, suggesting they originated from that region. By contrast, the Australian plants were not genetically similar to any native range samples, leaving their provenance uncertain. Interestingly, we identified two distinct P. aculeata lineages in Australia; one in NSW and South East Qld, and the other in Far North Qld. This pattern may suggest there have been two independent introductions of P. aculeata into Australia. We recommend that the biology of these two distinct lineages be studied independently, and that each be treated separately during host-range testing.