Floral Herbivory of Dryas octopetala by Svalbard Reindeer

Abstract

In polar semidesert communities of northwest Spitsbergen the reproductive potential of keystone vascular plant species, such as Dryas octopetala, is currently being constrained by low summer temperatures, resulting in the infrequent production of viable seeds. This study tests the hypothesis that summer foraging behavior of reindeer (Rangifer tarandus platyrhynchus) may further limit successful seed production due to intense selective grazing pressure on the flowering shoots. Surveys of neighboring coastal tundra areas with contrasting reindeer population densities revealed direct evidence of strong grazing pressure on reproductive shoots of D. octopetala on the Brøgger Peninsula and considerably less floral herbivory on the sparsely reindeer-populated Blomstrand island. Recruitment of Dryas on the Brøgger Peninsula is therefore being hindered by intense selective grazing of flowering shoots by Svalbard reindeer. This situation is not unique to this area of Svalbard and also extends to other species of flowering plants.