The Polyalthia is a genus in the family of Annonaceae, which are woody trees, shrubs and vines comprising about 130 genera and 2,300 species. During a field survey in Hongbenghe close to the China/ Myanmar border in Yingjiang County, Yunnan Province, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) and South China Botanical Garden (SCBG) found a new species of Polyalthia. They named it as Polyalthia yingjiangensis, after its type locality, Yingjiang county of Yunnan province, China.
After examining fresh and dried herbarium specimens, and consulting a large amount of literature, the researchers confirmed that the species is new to science.
Polyalthia yingjiangensis is a shrub with twigs pubescent, later become glabrous. It is most similar to P. miliusoides, a species known from Sabah and Brunei. Both species possess very long pedicels and have outer petals that are much smaller than the inner petals. The two species differ, however, in the indumentum of the perianth, thickness and indumentum of the pedicels, and the morphology of the dried monocarps. The abaxial surfaces of the perianth of P. yingjiangensis are densely hairy and the adaxial surfaces are glabrous, whereas both surfaces of the perianth of P. miliusoides are sparsely pubescent.
Polyalthia yingjiangensis is knownfrom three localities in Yingjiang County, Yunnan Province, close to the China–Myanmar border: Hongbenghe, Nabang, and Tongbiguan. It grows in forests at low elevations, from 350 m to ca 900 m above sea level.
Polyalthia yingjiangensis is classified as ‘Endangered’, and is only represented in herbaria by four collections from three localities in Yingjiang county where forests are severely fragmented.