Turbinicarpus  (Turbinicarpus subterraneus ssp. booleanus)

Classified as Critically Endangered (CR) on the IUCN Red List (1) and listed on Appendix I of CITES (3).

Turbinicarpus subterraneus spp. booleanus is a small, globular cactus with a tuber-like root, connected to the stem by a slender, underground neck (3) (4). Only around a third of the main stem body grows above ground (3). The stem is covered with green tubercles, which bear elliptical areoles at their tips. The areoles in turn bear 18 to 20 need-like ‘radial’ spines, which are glassy-white in colour with brown to reddish tips, and up to 0.6 centimetres in length, and also bear two central spines, which measure around 1.2 to 1.8 centimetres in length, are cylindrical with tapering ends, and are almost entirely brown to black in colour (3) (4). Seedlings are characterised by their elongated growth form, and only later develop a globular stem above the slender subterranean neck (4).

Turbinicarpus subterraneus ssp. booleanus is sometimes considered a full species, Turbinicarpus booleanus, rather than a subspecies of Turbinicarpus subterraneus (3).

This cactus is endemic to the Mexican state of Nuevo León, where it is found in only two, relatively close locations (3) (4).

Turbinicarpus subterraneus ssp. booleanus inhabits bare, exposed gypsum slopes in semi-desert, at elevations of around 1,860 metres (1) (3).

Measuring around two centimetres in diameter, the flowers of Turbinicarpus subterraneus ssp. booleanus are borne at the top of the stem, and are magenta in colour, with yellow anthers. The fruits are dark green to purple, and open along a longitudinal slit from which the small black seeds are released (3) (4).

This cactus is known from an area of just 5 square kilometres, and its population is estimated at fewer than 1,000 plants. The main threat to Turbinicarpus subterraneus ssp. booleanus is illegal collecting, a practice which is decreasing the number of individuals in the wild (1).

Turbinicarpus subterraneus ssp. booleanus is listed on Appendix I of the Convention on International Trade in Endangered Species (CITES), which includes species threatened with extinction, which are or may be affected by trade. Trade in this cactus should be subject to particularly strict regulation in order not to further endanger its survival, and must only be authorized in exceptional circumstances (3).

To find out more about Turbinicarpus species see:

• The Turbinicarpus Information Exchange:
  http://www.mfaint.demon.co.uk/cactus/turbo/
• Turbinicarpus.net Bildergallery:
  http://turbinicarpus.net/gallery/index.php