A remarkable range disjunction recorded in Metarungia pubinervia (Acanthaceae) Iain Darbyshire 1 , Kaj Vollesen 1 & Hazel M. Chapman 2 Summary. The first occurrence of the genus Metarungia Baden (Acanthaceae) in west Africa is recorded with the discovery of an isolated population of the widespread eastern African taxon M. pubinervia (T. Anderson) Baden in eastern Nigeria. The conservation status of this species is discussed. Key Words. Acanthaceae, Afromontane, Gashaka Gumti, Metarungia pubinervia, Nigeria. Whilst conducting ecological survey work within the Gashaka Gumti National Park and surrounding high- lands of Saurdauna Province, Taraba State, Nigeria in November 2002, one of the authors (H.M.C.) collect- ed a spectacular flowering Acanthaceous shrub from the remote Leinde Fadale Forest at c. 1600 m altitude. The specimen (H. M. Chapman 24) was subsequently brought to Kew for identification and was found to be referable to the genus Metarungia Baden, previously known only from three species in eastern and southern Africa (Baden 1981, under the illegitimate name Macrorungia C. B. Clarke). In view of the large disjunction in distribution, it was assumed that the Nigerian material would prove to represent a new species, although it was noted that the flowering material closely resembled the widespread east African taxon M. pubinervia (T. Anderson) Baden, and it readily keyed to that species in the revision of the genus (Baden ibid.). Further collections, including fruiting material, were requested and a second site visit was made in December 2003, where further flowering and mature fruiting specimens were collect- ed (H. M. Chapman 561). More detailed comparison of this material with M. pubinervia found the Nigerian gatherings to be inseparable from the east African material, with all measurements falling well within the range recorded for M. pubinervia by Baden (ibid.). Metarungia pubinervia was previously recorded over a broad distribution in eastern and southeastern Africa, from montane southern Sudan and southwestern Ethiopia, through the east African mountain chains and south to southern Zimbabwe and Mozambique where it was also recorded from major river catch- ments. Its westernmost extent was along the mountains bordering the Albertine Rift in eastern Congo-Kinshasa and Burundi (see Baden 1981, Fig. 1). The Nigerian population therefore represents a western range ex- pansion of approximately 1200 km. On the western fringes of its east African range, Metarungia pubinervia is often associated with mid- altitude (1000 – 1200 m alt.) forest typical of the Congo Basin, with dominant trees including Pterygota, Newtonia and Pseudospondias, whilst particularly in the SE part of its range it extends to lower altitudes within riverine forest. However, through much of its east African range it is most commonly associated with various montane and submontane evergreen forest assemblages up to 2000 m alt. Its distribution there- fore falls largely within the Afromontane phytocho- rion, a well-defined archipelago-like floristic region well represented in the mountain chains of east Africa and the Cameroon Highlands (White 1978, 1981, 1983). Range disjunctions of Afromontane taxa be- tween these two montane regions are well docu- mented and rather plentiful; for example Sebsebe et al. (2006) traced 12 species which occur in the highlands of Ethiopia and Cameroon but were absent in the intervening lowlands. Many of these are common Afromontane trees and shrubs, such as Agarista salicifolia G. Don (Ericaceae), Bersama abyssinica Fresen. (Melianthaceae), Nuxia congesta R. Br. ex Fresen. (Buddlejaceae) and Schefflera abyssinica (Hochst. ex A. Rich.) Harms (Araliaceae). However, some herbaceous taxa display a similar trend; for example Sebsebe et al. Accepted for publication October 2008. 1 Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, UK. 2 School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand. KEW BULLETIN VOL. 63: 613–615 (2008) © The Board of Trustees of the Royal Botanic Gardens, Kew, 2008