Ditrichum cornubicum

Range & Status

(syn. ' ? Dicranella sp.' of Paton, 1969). Until recently regarded as one of Britain' s few endemic mosses, known only from Cornwall and very rare here. However, a small population was discovered in SW. Ireland (W. Cork) in 2006, where it is likely to be a recent accidental introduction from Cornwall (Holyoak, in preparation).

Regional Distribution

Discovered in 1963 on a roadside west of Lanner (SW73) (Paton, 1976), but now extinct there. Found in 1965 on mine-spoil at Phoenix United Mine near Minions (VC2; SX27) and in 1997 at Crow' s Nest.

Habitat & Ecology

The Lanner site was on mine-spoil used to surface a small roadside lay-by. Near Minions and Crow' s Nest it has been found on paths and tracks within a large area of minespoil. Analytical data reported by Holyoak et al . (2000) show high concentrations of available copper in the substrata on which it grows at Minions and further document the conclusions of Paton (1976) that: ' D. cornubicum is a pioneer species, and at Minions it grows on compacted, moist but well-drained peaty or loamy soil, mostly in areas where the vegetational cover is either relatively open or sparse. Scattered stems occur also in dense mats of other bryophytes, but because of its diminutive size, it is unable to survive strong competition for any length of time.' Sporophytes are unknown (only male plants

have been found). Rhizoidal tubers are abundant in specimens collected from the wild and cultivated plants produce gemmae on aerial protonemata (Paton, 1976; Whitehouse, 1980; Arts, 1994); either of these could serve as a means of aestivation, as propagules allowing dispersal, or both.

Threats

A colonist of nearly bare ground that apparently varies in abundance from year to year. In view of its rarity, unscrupulous (illegal) collecting could pose a real threat to its survival. Vegetation succession on open ground poses a threat to the species, especially if nutrient levels increase. At Phoenix United Mine accumulated dung from sheep resting on tracks has led to eutrophication and thicker cover of large mosses. Exclosures have recently been erected to exclude the sheep and a programme of work ensures the large mosses are scraped away so that the ground surface remains open.

Conservation

The sites at Phoenix United Mine near Minions and at Crow' s Nest are both protected as SSSI and SAC. English Nature and its successor Natural England have carried out regular population monitoring at both localities and ongoing habitat management to benefit the species is being carried out at Phoenix United. D. cornubicum is listed as Endangered on the UK Red-list (Church et al ., 2001), covered by the UK BAP, and protected under Schedule 8 of the Wildlife and Countryside Act 1981. The species has been included in ex-situ conservation projects based at RBG Kew, where living material is being maintained in cryogenic storage.