The Composition of the Beetle and Spider Faunas on Fragmented Heathlands

Abstract

The catches of invertebrates (mainly Coleoptera and Araneae) from 23 heathlands [England, UK] were examined a identify any systematic variation in their composition. Compositional changes were investigated by ordination techniques and recognizable patterns of variation related to the areas of the heathlands, the extent to which they were isolated from one another and the composition of their vegetation. For vegetation 33% of the total variation could be attributed to the distribution of dwarf species of Ulex and a further 21% to the percentage cover of Erica tetralix, and hence, possibly, to gradients in soil moisture. For the sets total beetles and total spiders variation in species composition could not be reduced to a few dimensions, in both cases the first axis of variation was correlated with the total area of adjacent heathland. The variation in the species composition of the set total spiders was also correlated with the total area of adjacent heathland and with the percentage cover of Ericaceae. For heathland spiders 23% of the variation depended on the area of adjacent heathland. Furter analysis of the data for heathland spiders showed that those species with the poorest powers of dispersal were confined to the large heathlands, and were absent or poorly represented on the small ones. There were no species occurring on small heathlands which did not occur on the large ones.