Studies on the invertebrate fauna of fragmented heathland in Dorset, UK, and the implications for conservation

Abstract The dwarf-shrub heathlands of Dorset (southern England) are an example of a semi-natural community which has been reduced in extent and fragmented. The remaining fragments of heathland now exist in a matrix of farmland, forest and urban land. This paper summarises investigations into the diversity and composition of the invertebrate fauna of heathland fragments of different sizes and with different degrees of isolation from other heathland. In general, there was a negative correlation between the point diversity of invertebrates and both fragment area and the area of surrounding heathland (a measure of isolation). It was also shown that invertebrate diversity depended on the structure and composition of the vegetation surrounding the fragments. These studies suggested that such fragments should be viewed as components of an interacting matrix and that the interaction between the fragment and its surroundings was an important factor to be considered in conservation practice. This concept is developed more generally in the context of reserve selection. It is argued that besides making judgements based on traditional criteria the interactions, both physical and ecological, between fragments and their surroundings should form part of the selection process.