SPIDER DIVERSITY AND ASSEMBLAGES IN DIFFERENT AREAS OF THE MOUNTAIN FOREST (ìSELVA MONTANAî) ALTITUDINAL FLOOR OF THE YUNGAS ECOREGION OF SALTA PROVINCE, ARGENTINA

GONZALO DANIEL, RUBIO; CORRONCA, J. A.

Congreso; 17Th International Arachnological Congress, Sao Pa; 2007

International Arachnological Society

Yungas ecoregion has a high endemism and the ìmountain forestî (700 - 1,500 m a.s.l.) is one of its altitudinal floor poorly studied, and the most diverse floor of this ecoregion. Here we study the spider diversity and assemblages in different studied areas of the mountain forest and between different sites of the same area, considering two vegetation strata on each site. The samples were taken by a G-Vac during the autumn of 2006. Five samples were taken in the lower stratum (0 ñ 1 m) and five in higher (1 - 2.5 m) on each of the eight sites of three different areas of the mountain forest of the Yungas, Salta Province, Argentina: Reserve of San Lorenzo (SL) (three sites), El Carmen (EC) (three sites) and Cerro 20 de Febrero (C20F) (two sites). Eight hundred and seventy five spiders of 17 families (71 spp./ morphospecies) were collected. Theridiidae (n = 99, S = 15), Araneidae (n = 80, S = 12), Anyphaenidae (n = 70) were the most abundant and diverse families. Comparing the species richness and the relative abundance, the values showed EC>C20>SL with significant differences between them (Bootstrapping method P < 0.05), but in abundance and species richness only between SL-C20F and EC-C20F. The Shannon and Simpson indexes showed significant differences between SL-C20F, and SL-EC recorded more similarity in the spider assemblage (Morisita Index = 0.69). If we compare the different sites of each studied area, we observed a significant difference in the spider abundance in EC. All the studied sites of SL were very different in relative abundance and dominance, meanwhile the sites of C20F varied only in species richness. Analyzing the assemblages similarities in the 8 studied sites of the yungas, the cluster resulted in two groups (SL-EC and C20F) (Bray-Curtis similarity = 0.81 and 0.83, respectively), and the sites of SL were the most similar. The spider assemblage between the vegetation strata was different (Mann-Whitney-U p = 0.034), including all the calculated diversity measures the similarity between them was moderate (Jaccard = 0.45). The diversity and spider assemblage of the studied areas were different as same as the spider taxonomical composition between vegetation strata