The conservation of variation in geographically peripheral populations:: Lloydia serotina (Liliaceae) in Britain

Peripheral populations of widespread species can hold important reserves of variability despite their often small size and isolation. Lloydia serotina occurs in peripheral populations in north Wales, UK, where it is given special protection despite occurring more widely in the northern hemisphere. Population dynamics, reproduction and genetic variation, using isozyme analysis, were studied in two small Welsh cliff habitat populations and in 13 populations in the centre of its range in the American Rocky Mountains and the European Alps, to assess the status and performance of the Welsh populations compared with those in its more typical alpine habitats. The smaller populations showed lower flowering and seed production percentages, but sexual reproduction does take place in all populations and the seed produced is viable. The smaller populations had lower levels of allozyme variation, but variability was present in all populations except one small, isolated one in North America. There was significant genetic differentiation among the populations, particularly between those from Wales and the Alps and between the two Welsh populations studied. Analysis of RAPID variation in four, small Welsh populations provided further evidence of this differentiation. The results indicate possible effects of glacial and post-glacial periods in isolating small populations and, together with genetic drift, promoting genetic divergence. This differentiation suggests the need to conserve these small populations as separate entities, increasing their size by habitat management rather than any direct intervention. (C) 2001 Elsevier Science Ltd. All rights reserved.