Distribution and dynamics of surface-dwelling spiders across a pasture-plantation ecotone

The influence of the interface between different vegetation types on the surface active spider fauna within a grass pasture-coniferous plantation ecotone was sampled by pitfall trapping. Species abundance, richness and diversity relative to pitfall traps were measured along a transect across the ecotone. Spider species were classified into six categories based on their habitat preference and the influence of the non-preferred habitat. The number of individuals trapped progressively decreased from the pasture across the interface to the plantation habitat. Species richness increased by some 72% and diversity by some 141% at the interface. These increases were attributable to both the overlap of pasture and plantation species invading the non-preferred habitat across the interface, and to the presence of species with a preference for the ecotone. The overlap of pasture and plantation species was found to be the larger part of the spider community at the interface, species classed as ecotone accounting for only 25% of the catch at the interface. Distinct spider species assemblages were found in the pasture and plantation habitats, and the interface species composition was more similar to the plantation than to the pasture. The variation in physical and biological characteristics which the interface induces, and their influence on the spider assemblages found, are discussed in relation to other ecotone studies.