Flora

About 815 species are now known from Soqotra of which between 230 and 260 are endemic (including some fifteen species restricted to Abd al Kuri). This compares with a total of 565 species, of which 206 were endemic, collected by Balfour and Schweinfurth in 1880-1 (Balfour 1888). Soqotra falls within the Somalai-Masai centre of endemism of White who comments that enough species are confined to the island to make it stand out as a local centre of endemism. There is one subendemic family - the Dirachmaceae (recently a second species has been found in Somalia) and ten endemic genera: Angkalanthus, Ballochia and Trichocalyx (Acanthaceae), Duvaliandra and Soqotranthus (Asclepiadaceae), Haya (Caryophyllaceae), Lachnocapsa (Cruciferae), Dendrosicyos (Cucurbitaceae), Placoda (Rubiaceae) and Nirarathamnos (Umbelliferae). The families richest in endemics are Compositae (26), Acanthaceae (24), Euphorbiaceae (21), Labiatae (20) and Asclepiadaceae (11).

Since the first pioneering botanical expeditions of Isaac Bayley Balfour in 1880 and Georg Schweinfurth in 1881 Soqotra has been famed for its botanical curiosities. Perhaps the most notable of these are the podagrics or swollen-stemmed trees, these include: Dendrosicyos socotranus - which somewhat resembles a small baobab; Dorstenia gigas and Adenium obesum ssp. socotranum. One of the most interesting trees, and an important potential genetic resource is Punica protopunica. This is related to the pomegranate (P. granatum) but has smaller and less palatable fruits and is the only other species in the family Punicaceae. Several species on Soqotra are of horticultural interest for instance Begonia socotrana, the hybrid parent of winter-flowering begonias, and Exacum affine - the Persian violet.

The Soqotran flora has strong links with adjacent parts of Somalia and Arabia but some species and genera have interesting disjunct distributions: Dracaena cinnabari, the Dragon's Blood tree, is a tertiary relict with related species in southern Arabia, north-east Africa and the Canary Islands; species of Kalanchoe and Helichrysum show strong links with southern African species but perhaps the most strange distribution is that shown by the genus Thamnosma with T. socotrana on Soqotra and related species in southern Arabia, SW Africa and SW North America. The Soqotran flora includes plants which can be considered taxonomic relicts, that is with no close relatives, these include: Dirachma socotrana, one of only two species in the Dirachmaceae, a family related to the Malvaceae (Link: 1991; Bazara'a et al.: 1991) but with an interesting mixture of characters including 8-merous flowers, stamens opposite the petals and fruits with a dehiscence similar to that found in Geranium; Dendrosicyos Soqotranus the only arborescent member of the Cucurbitaceae and Wellstedia a small shrub of boraginaceous affinities but which is sometimes placed in a family of its own.

The endemics are found throughout the island and in all vegetation types. The commonest plants on the island (Croton Soqotranus and Jatropha unicostata) and most of the characteristic species, including almost all of the common shrubs and trees are endemic. However, the richest areas for endemics are the limestone plateaus and granite Haggier mountains.