Ground-living spiders in wooded habitats under human influence on an island in Finland

Abstract

doi: 10.5431/aramit4503 Abstract. Spiders were collected by pitfall traps in the south-western archipelago of Finland. Wooded study habitats on a small-sized (1.2 km 2 ) island were: 1) natural open ash grove, 2) dense mixed grove (old overgrown wooded meadow), 3) wooded aspen pasture and 4) wooded meadow, both restored ten years earlier, 5) natural wooded meadow. Highest species and family numbers were found at the natural sites (1 and 5) and the lowest in the dense grove (site 2). Linyphiidae dominated, both at species and individual level, in the groves. Lycosidae were abundant on the wooded meadows and Gnaphosidae on the wooded pasture. The highest faunal similarities were between the groves (70 % species in common) and between the wooded meadows (64 %). The lowest similarity was found between the dense grove (17 %) and the ash grove (23 %) with the aspen pasture. Ten years after clearing, sites 3 and 4 had diverse spider faunas. The fauna at site 4 resembled that on the corresponding natural site (5), thus showing restoration success. Altogether 84 species of spiders were caught. The proportion of Gnaphosidae (16 species found) is high. Most species found in the study are common in south-western Finland and many occur across the whole country. Pardosa lugubris was most dominant at three sites, P. pullata and Diplostyla concolor both at one site. Two species, Enoplognatha thoracica and Micaria fulgens, are included in the Finnish Red Data Book.