Invertebrate Diversity on Fragmented Calluna Heathland

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Abstract
Invertebrates were sampled from mature, dry Calluna heathland in southern England [UK] by pitfall trapping and vacuum sweep netting. Sampling sites were chosen on 22 heathlands which differed in their total areas and the extent to which they were isolated from other heathlands. A significant negative correlation was found between the richness of plant species at a point and both the areas of the heathlands and the amount of other heathland within a 2 km radius of the sampling point. Coleoptera (272 spp.) showed significant negative correlations between species richness at a point and both areas of the heathlands and the area of heathland within a 2 km radius. Similar, but more highly significant, correlations were obtained for phytophagous Coleoptera (65 spp.). For all Araneae, no significant correlations were obtained between species richness at a point and the area of the heathlands or the area of a heathland within a 2 km radius of the sampling point. For heathland Araneae the evenness of the species abundance deceased with increasing area. On large heathlands, spiders contributed a larger proportion to the total spider fauna, than on small ones. Multiple regression analysis suggested that the number of species of Coleoptera was dependent on the cover of Ulex spp., but no other features of the vegetation. For Araneae vegetation height was the most important regressor.