Which species of ‘Conyza’ (Erigeron) occur in Australia?

Several species of the genus Erigeron (Asteraceae) have become established as weeds in Australia, some of these becoming invasive. Uncertainty remains about the identity and taxonomy of some species formerly placed in Conyza. Australian floras and checklists recognise Erigeron bilbaoanus, but taxonomists in other countries consider the name a synonym of Erigeron floribundus. Likewise, the Australian Plant Census (and the Flora of North America) treats Erigeron pusillus as a synonym of Erigeron canadensis, but some Australian state and territory checklists recognise this as a distinct species. We use target capture data to infer species limits and the genetic relatedness of lineages in ‘Conyza’ introduced to Australia. Results indicate that Erigeron pusillus and Erigeron canadensis in Australia are more genetically differentiated than the other related and widely accepted species of the genus. Therefore, these taxa should be accepted as distinct at the species level. The species currently recognised as Erigeron bilbaoanus in Australia matches the lectotype of Conyza floribunda, and Australian taxonomy should be updated accordingly. At least in Australia, Erigeron floribundus shows the largest degree of genetic admixture of the five study species. To support accurate identification and further research, we provide an updated identification key to Erigeron of Australia.