Genetic variation in the Red-Listed moss Ditrichum cornubicum Paton (Ditrichaceae) and implications for its conservation

Ditrichum cornubicum is a rare and threatened acrocarpous moss found on copper-rich mine waste, characteristic of the EU protected habitat ‘Calaminarian grassland of the Violetalia calaminariae’. The species was once thought to be a British endemic, being known from two former copper/tin mine sites in Cornwall, until the discovery of a population in 2006 at Allihies Mountain Mine, Co. Cork, Ireland, a former copper mine. In light of this discovery, two theories of possible introduction from Britain to Ireland were put forward: (1) an introduction from the 1800s and (2) a more recent introduction (2000s). Only male plants of the species are known, and reproduction and dispersal are therefore solely through asexual propagules and fragmentation. In order to address the conservation questions of the origin of the Irish population and to determine whether diversity exists within this rare species, genetic fingerprinting (amplified fragment length polymorphism) was carried out on the three known global populations. Percent polymorphism was found to be 7.29% and Nei's total gene diversity (H_T) was 0.0356. AMOVA revealed that, of the small amount of variation found, the majority was among the three populations (98%). The presence of five private alleles in the Allihies population suggests a longer period of isolation than would fit either theory of introduction. Cluster analyses reveal that the Allihies population is more genetically distinct than the two British populations are to each other, thus heightening the conservation priority for this population.