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

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