Genetic data confirm the presence of Senecio madagascariensis in New Zealand
The Senecio inaequidens – S. madagascariensis complex (Asteraceae: Senecioneae, subsequently “fireweed complex”) is a group of six southern African species of Senecio, three of which are considered invasive in various parts of the world: S. madagascariensis in South America, Japan, Australia, and the Hawaiian Islands, S. skirrhodon in New Zealand, and S. inaequidens in Mexico and Europe. Morphological plasticity and historically limited access to reliable information in the introduced ranges have led to taxonomic confusion in many countries, where the weedy populations have been classified under changing names and sometimes erroneously considered to be native species. This confusion has hampered research into management options such as biological control. Recently, uncertainty has arisen about whether only one or two species of the fireweed complex are present in New Zealand. To resolve this question and test the utility of multi-locus sequence capture data for the understanding of the complex, we produced a first dataset of hundreds of genes for four of its species with a focus on S. madagascariensis and S. skirrhodon. Both species were found to be present in the North Island of New Zealand, with S. madagascariensis widespread in the Northland region and S. skirrhodon present at both sites sampled in the southern half of North Island. Our results show that sequence capture data provide high levels of confidence and resolution even at shallow phylogenetic levels, which will enable a greater understanding of the fireweed complex and its invasion history as the dataset is expanded.