Cheniella gen. nov. (Leguminosae: Cercidoideae) from southern China, Indochina and Malesia

Abstract

For much of the last thirty years, the caesalpinioid genus Bauhinia has been recognised by numerous authors as a broadly circumscribed, ecologically, morphologically and palynologically diverse pantropical taxon, comprising several subgenera. One of these, Bauhinia subg. Phanera has recently been reinstated at generic rank based on a synthesis of morphological and molecular data. Nevertheless, there remains considerable diversity within Phanera. Following a review of palynological and molecular studies of Phanera in conjunction with a careful re-examination of the morphological heterogeneity within the genus, we have found strong evidence that the species of Phanera subsect. Corymbosae are a natural group that warrant generic status. We describe here the genus Cheniella R.Clark & Mackinder gen. nov. to accommodate them. It comprises 10 species and 3 subspecies, one newly described here. Generic characters include leaves that are simple and emarginate or bilobed; flowers with elongate hypanthia which are as long as or much longer than the sepals; pods that are glabrous, compressed, oblong, indehiscent or tardily dehiscent; and with numerous seeds, the seeds bearing an unusually long funicle extending most of the way around their circumference. A further distinctive floral character was found to be a fleshy disc on which the staminodes are mounted. An analysis carried out for this study reveals Cheniella to be characterised by a pollen type that is unique to the genus and previously unknown in the Leguminosae. Species diversity is richest in southern China, the full distribution extending westward to India and south- and eastward through Indochina into Malesia.