Comparison of the spider community in an smallholding of the Valle de Lerma, Salta (Argentine) in different plots and hedgerow.

CORRONCA, J. A.; OLIVO VERÓNICA,; GONZÁLEZ REYES, ANDREA XIMENA

Sao Pedro

Congreso; 17Th International Arachnological Congress, Sao Paulo, Brazil; 1997

Spiders are an important generalist predator group very abundant in several crops and exert an excellent natural control to polyphagous phytophagous arthropods. In Argentina, few studies were made about the spiders in agroecosystems. This study aims to analyze the diversity of spiders and their variation, the guild composition and variation from May 2004 to March 2005 in an smallholding of the Valle de Lerma, Salta, Argentine using biweekly samples with a pitfall trapping and a G-Vac. The studied area included 5 ha with an strawberry plot, old field plot and hedgerow surround them. The material was separated in morphospecies using a digital pictures database generated by Taxis 3.5, and later into families and guilds. The data were analyzed using PAST, BiodiversityñPro and XLSTAT software. A total of 1,721 spiders (20 families and 117 morphospecies) were collected: Amaurobiidae (N = 6, S = 1), Anyphaenidae (N = 247, S = 8), Araneidae (N = 246, S = 19), Corinnidae (N = 64, S = 5), Hahniidae (N = 9, S = 3), Linyphiidae (N = 91, S = 8), Lycosidae (N = 153, S = 8), Mimetidae (N = 2, S = 1), Miturgidae (N = 1, S = 1), Oxyopidae (N = 168, S = 5), Palpimanidae (N = 13, S = 1), Philodromidae (N = 30, S = 1), Pholcidae (N = 9, S = 3), Saltcidae (N = 176, S = 18), Sparassidae (N = 1, S = 1), Tetragnathidae (N = 23, S = 6), Theridiidae (N = 325, S = 15), Theridiosomatidae (N = 2, S = 2), Thomisidae (N = 149, S = 10) and Zodariidae (N = 4, S = 1). The diversity index and equity index J, between the studied areas showed a non-significant difference, but Berger-Parker index showed a significant difference (P = 0.05) between strawberry-old field and strawberry-hedgerow. The Jaccard index showed more similarity between strawberry-old field (Jaccard = 0.663). The most abundant families were: Theriididae (29.48%) in strawberry, Anyphaenidae (18.14%) in old field, and Anyphaenidae (20.37%) in hedgerow. Stalkers was the best represented guild in the three studied areas, but space web builders and orb weavers were for the strawberry plot and the foliage runners to the other areas Araneidae showed to be more sensitive to pesticides reducing their density. This family and Theriididae increased the density after the last pesticide application in the strawberry plot.