XENOSTEGIA D. F. Austin & Staples, Brittonia 32: 533. 1980
Merremia sect. Halliera O'Donell, Lilloa 6: 472. 1941.
Xenostegia tridentata (L.) D.F. Austin & Staples.
Tropical regions of Asia, Africa, Australia and the Pacific; introduced and naturalized on Puerto Rico in the Caribbean. map
Xenostegia tridentata is extraordinarily variable, which has led to naming of many taxa based on seemingly distinctive morphotypes. In Africa 3 infraspecific taxa are recognized; in Asia all the variation is accommodated in a single polymorphic species. In contrast, X. medium is rather constant in its morphology and is easily distinguished from its congener by the enlarged outer sepals.
Long included in the polyphyletic genus Merremia, these 2 species are distinctive in terms of pollen apertures, seed germination, cotyledon shape, stigma micromorphology, and seed characters; in 1981 they were segregated as genus Xenostegia.
Austin & Staples, Brittonia 32: 533-536. 1980.
R.C. Fang & Staples in C.Y. Wu & P.H. Raven (eds.), Fl. China 16: 300. 1995.
Lejoly & Lisowski, Fragm. Flor. Geobot. 38: 379. 1993.