The Trachyspermums of Socotra

Introduction
Socotra is a dry tropical island of approximately 3625 km2 lying in the Indian Ocean (12° 30'N, 54° 00'E), E of Somalia and SE of the south coast of Yemen. The climate is monsoonal with strong winds effectively isolating the island from the mainland in the summer months. The long geological separation of Socotra from the mainland, coupled with the powerful evolutionary pressures of its harsh environment, have resulted in a fascinating flora of some 830 species, over one third of which are endemic. The first botanical explorations were made by Sir Isaac Bayley Balfour in 1880, and since then only a few collections have been gathered from Socotra, or the small nearby islands of Abd al Kuri, Samhah and Darsah which comprise the Socotran Archipelago. Since 1989 the Royal Botanic Garden, Edinburgh has mounted a series of major botanical expeditions to the archipelago led by Anthony Miller. These have greatly enhanced knowledge of the flora, as well as discovering novel taxa, and assessing conservation status. This current paper is the result of studies undertaken during the preparation of the Umbelliferae for the Flora of Arabia, and the Ethnoflora of Socotra (Miller, Morris & Alexander in prep.).

Authors
Mark Watson, Edinburgh, U.K. 
Emma Barclay, Edinburgh, U.K. 

Scheduling
Work complete.

Publications arising from this work
Barclay, E L. & Watson, M.F. (1998). A revision of Carum and Trachyspermum (Umbelliferae) in the Socotran Archipelago. Kew Bulletin 53(4): 897-907. 

Herbarium collections of annual umbellifers from the Socotran Archipelago have been variously attributed to species in Carum (C. calcicolum Balf. f., C. kuriense Vierh., C. pimpinelloides Balf. f., and C. trichocarpum Vierh.), or the corresponding combinations in Trachyspermum. Recent gatherings have been examined alongside the historic material, using fruit anatomy, scanning electron microscopy and classical morphology. Results show that this endemic species complex should best be treated as one variable species Trachyspermum pimpinelloides (Balf. f.) H. Wolff.