Out of South America: genetic insights into the introduction histories of Cardiospermum balloon vines in Australia

The successful management of invasive alien species is hampered when they share habitats with native congeners. However, in some instances, the status of resident congeners (as alien or native) in the invaded range is unknown, further complicating management efforts. Here, we investigate the genetic relationships between Cardiospermum balloon vine species, focussing on C. grandiflorum and C. halicacabum, to better understand the introduction histories of these species and the status of C. halicacabum in Australia. Cardiospermum grandiflorum is considered to be an invasive species in the country while the status of C. halicacabum is debated. Based on network and phylogenetic analyses of chloroplast and nuclear gene sequencing data, respectively, we infer an alien status for C. halicacabum in Australia and show that multiple introductions likely founded invasive populations of both balloon vine species in the country. We discuss our findings in the light of the management of balloon vines in Australia, with an emphasis on biological control.