Distributions of Species in theTegenaria atricaGroup (Araneae: Agelenidae) in North-East England: Chance, Contingency and Priority

Abstract

Summary Tegenaria atrica is a species common in continental Europe and the Republic of Ireland but on the British mainland it has long been regarded as a relatively rare import that has failed to establish. The recent discovery of this species in some numbers and over several years in Burnopfield, County Durham, represented the first-reported, self-sustaining population. We show here that the species is widespread across a large swathe of country comprising parts of north County Durham, Tyne and Wear, and south-east Northumberland — an area of some 710 km2. Within a core range of approximately 400 km2, the other species in the Tegenaria atrica group, T. saeva and T. gigantea, tend to be uncommon or absent. The distributions of these three closely related species raise questions regarding the origins of the T. atrica population, the effect of chance and priority in initial establishment, and the role of possible competitive interactions between them. Although determining ecological processes from present p...