Pollen diversity of Xenostegia D.F.Austin et Staples (Convolvulaceae)

Abstract

Abstract Xenostegia D.F.Austin et Staples is a small genus in the family Convolvulaceae, with five species restricted to Africa, and one species widespread across the Paleotropics. It was initially established to accommodate two species in Merremia that possessed non-spinulose pantoporate pollen, rare in the family, along with stigma and anther characters that did not fit other genera entirely. Recent molecular studies, and the discovery of a new species in Central Africa, have expanded the delimitation of this genus from two to six species. Our survey captures the palynological variation of all currently documented species of Xenostegia, revealing that more types of pollen aperture patterns are present (15- and 30-colpate), with implications for the circumscription of the genus. In addition, a unique pattern of exine sculpture (plurigemmate-echinate) was discovered, which is shared by all the species and has not yet been documented in any other member of family Convolvulaceae.