Two New Species of Hyparrhenia (Gramineae) from Ethiopia

Abstract

Summary. Two new species, H. neglecta and H. claytonii, are described from the Ethiopian highlands and their position within the genus is discussed. Hyparrhenia is a large genus of predominantly African savanna grasses, notorious for the indistinctness of many of its species due to extensive introgression. In these circumstances intermediates are commonplace, leading to difficulties in identification, and new species can only be described with caution. However, the two specimens described here, each as a new species, show distinctive characteristics clearly delimiting them from other members of the genus. They have come to light during the preparation of the grass account for the Ethiopian Flora Project. A majority of Hyparrhenia species are tall tussocky perennials, well suited to wooded grassland subject to a seasonal rainfall regime. The basal tussock protects the perennating buds from the heat of the regular dry-season fires. The annual habit is relatively infrequent, but interestingly a high proportion of these annual species occur in Ethiopia, often as endemics or at least with their distribution centred there. Indeed, Ethiopia seems to be a minor centre of diversity in Hyparrhenia, where the genus has escaped from the constraints of the savanna, speciating particularly in the direction of an annual habit. Unfortunately collections from the northern part of the Ethiopian highlands are still very sparse and our knowledge of variation there is necessarily limited. It is therefore not surprising that new species should still be discovered in this part of the range of the genus. Hyparrhenia neglecta S. M. Phillips sp. nov., gramen annuum sect. Hyparrhenia pertinens, speciebus aliis sectionis (H. coleotricha excepta) paribus racemorum quadriaristatis differt, affinis H. coleotricha sed gluma inferiore spiculae sessilis linearo-oblonga coriacea glabra, pedunculi barba lutea, aristula spiculae pedicellatae 4 - 5 mm (nec 6 - 8 mm) longa differt. Typus: Ethiopia, Quartin Dillon & Petit 66 (holotypus K). Slender annual; culms 45-55 cm high. Leaf-blades linear, 3-4 mm wide, glabrous; ligule truncate, c. 1 mm long with adnate triangular sheath-auricles, pallid. Spatheate panicle loose, sparse, composed of 5 - 8 raceme-pairs; spatheoles narrowly lanceolate, 5-6 cm long; peduncle /3 spatheole length, arching at maturity, bearded with yellow hairs. Raceme-pairs stoutly 4-awned, deflexed at