Palynology, cytology, and molecular systematics of Anemone section Begoniifolia (Ranunculaceae)

The circumscription and phylogenetic relationships of the Anemone section Begoniifolia have long been in dispute. Here, we use molecular data and palynological and cytological observations to test the monophyly of the section and evaluate phylogenetic relationships within the section. Three pollen types were observed in the section: Anemone sumatrana is 3-colpate; A. hokouensis, A. howellii, and A. orthocarpa are 6-colpate; and A. begoniifolia and A. xingyiensis are pantoporate. All six species have the chromosome number 2n = 16 and essentially uniform karyotypes (2n = 10 m + 4st + 2t). Nuclear ITS and plastid atpB-rbcL DNA sequences were analyzed using maximum parsimony, maximum likelihood, and Bayesian inference methods. Within Anemone s. l., two strongly supported clades corresponding to subgenera Anemonidium (x = 7) and Anemone (x = 8) were recovered. Our results indicate that section Begoniifolia is better treated at subsectional rank and is one of four subsections (Begoniifoliae, Rupicolae, Rivulares, and Vitifoliae) within section Rivularidium of subgenus Anemone. Subsection Begoniifoliae is relatively well supported and includes A. begoniifolia, A. hokouensis, A. howellii, A. orthocarpa, A. sumatrana, and A. xingyiensis. We present a formal reclassification of section Rivularidum, including two new combinations: subsections Begoniifoliae and Rivulares.