Biogeographical and evolutionary insights on Erigeron and allies (Asteraceae) from ITS sequence data

Complex geographical distribution patterns and agamospermy have united to obscure systematic relationships in the genus Erigeron (400+ species). Sequence data were analyzed from the internal transcribed spacer region of nrDNA (ITS) and 5.8S cistron for 77 taxa including 63 Erigeron species. Results support the North American origin of Erigeron and document that Aphanostephus, Conyza, and three small genera restricted to South America (Apopyros, Hysterionica, Neja) are all derived from within Erigeron. Phylogenetic data indicate that agamospermy has arisen at least three times in Erigeron and that autogamy has evolved independently in Conyza and in E. sect. Trimorpha.