Influence of landscape diversity and agricultural practices on spiderassemblage in Italian vineyards of Langa Astigiana (Northwest Italy)

The purpose of this study was to investigate spider assemblages of the Italian vineyards of Langa Astigiana (northwest Italy). Pitfall trapping and standardized hand collecting were combined to have an overall idea of the spider fauna living in this agroecosystem. A total of 138 samples for pitfall sampling and 92 for hand collecting sites were collected at 23 different times over a period of 2 yr (2003 and 2004). The vineyards differ mainly from agricultural practices (certified organic production, production according to EECÕs Council Regulation 2092/91 on biological agriculture and intensive production) and for the heterogeneity of landscape matrix surrounding them. We studied the influence of these two factors on spider assemblages applying canonical correspondence analysis and multiresponse permutation procedures (MRPPs). Significant results of MRPP were analyzed in terms of hunting strategies. Significant differences are found among groups according to both landscape heterogeneity and agricultural practices, the first resulting more significantly. Analyzed in terms of hunting strategies, an increase in landscape heterogeneity seems to provide an increase in ambush spiders and specialized predators, whereas an increase in sheet web weavers seems to be related to homogeneous landscapes.