Survival and Flowering of Primula Scotica Hook

Abstract

(1) Primula scotica risks extinction in many of its few remaining sites. It is successful only in a small range of habitats within a limited area. Even within habitats where the species can readily be found, flowering frequency can be very low and population numbers can decline in unfavourable years. (2) Plants in permanently marked quadrats were of two subpopulations: (a) those plants which were present at the beginning of a sixteen-year monitoring period ('original plants') and are distinct in having high flowering frequencies and longer life-spans; and (b) those which appeared in the quadrats during the period of study ('new arrivals') and although many can persist for several years they achieve only very low flowering rates with the majority of individuals remaining vegetative. It is suggested that because of the increased likelihood of selfing in years of poor flowering there can arise a genetically inferior subpopulation which may for a time reduce further the vigour of an already depleted population. (3) The number of plants that flower in any year, the population size and the number of seedlings established, show positive rank correlations with mild winters and negative rank correlations with increased snow-fall, snow-lie and gale frequency. A net gain in population size in the marked quadrats during the sixteen-year monitoring period was achieved only in four years of mild winter weather between 1970 and 1973. (4) Despite the general increase in global temperatures this century, northern latitudes from 50^N have experienced a progressive temperature reduction since 1950 and this current cooling trend in the North Atlantic, should it continue, will be a serious risk for the maintenance of viable populations of P. scotica. (5) There is clearly a need for providing long-term habitat stability for the conservation of this rare endemic species.