Tangled evolutionary history: genetically divergent taxa and hybrids characterise lantana invasions in Australia

Aim: to investigate population genomics and phylogeography in invasive lantana, including its taxonomy, spatial distribution, and patterns of morphological and genetic variation across the Australian continent. Location: the main area invaded by lantana on the Australian continent, i.e., coastal and subcoastal eastern Australia from northern Queensland to southern New South Wales up to approximately 100 km inland, across 22 degrees latitude. The native range of lantana in the Americas was also represented. Methods: we used DArTseq to generate genome-wide single nucleotide polymorphism (SNP) data for >600 individuals representing the native and Australian invaded ranges of lantana. We analysed data from >20,000 SNPs to identify distinct genetic clusters, and test the extent to which they corresponded with taxonomic descriptions and morphotype concepts used in lantana biological control. Genome sizes were estimated for a small representative subset of individuals using flow cytometry. We used MaxEnt to estimate habitat suitability for different lantana genetic clusters, and compared these predictions with observed patterns in biological control agent host-specificity. Results: invasive lantana in Australia consisted of several divergent genetic clusters of most likely tetraploid individuals. Gene flow between genetic clusters was limited, consistent with the notion that multiple species introductions and/or hybridisation events were part of the invasion history. Two widespread, homogeneous genetic clusters were found to be dominant in Australia; two other genetic clusters with more limited distributions were identified with potential for future spread. Biological control agent host preferences were consistent with identified genetic clusters. Main conclusions: treating invasive lantana as a single taxon may be counterproductive for effective management. Comprehensive taxonomic revision is needed to enable more precise identification of invasive taxa. Improved identification will support improved management, particularly if using biological control.