Spiders (Arachnida: Araneae) associated with two degraded forests in the humid Chaco of Corrientes, Argentina. The advancing degradation of the forest in the biogeographic Chaco province (Argentina) produces an important loss of its little known biodiversity. We studied the spider biodiversity in two forests of Corrientes, Argentina's "Distrito Oriental Húmedo del Chaco": Laguna Brava and El Perichón. Seasonal samplings of foliage and fallen leaves between 2001 and 2002 produced 2 067 individuals from 33 families and 226 species/ morphospecies). The families Araneidae, Anyphaenidae, Salticidae and Theridiidae were the most abundant in both forests. The "orb weavers" guild had the highest number of specimens (n=382) and "stalkers" the highest richness (S=56). in Brava, highest abundance was in the summer (n=287) and spring (n=273), in Perichón, it was in winter (n=315). The specific richness and the diversity indexes were higher in

Spiders are a megadiverse group that can be useful indicators of the overall species richness and health of biotic communities. The spider diversity in subtropical forests of the Neotropical region are not yet well known, especially in Argentinean subtropical forests where systematic fieldwork has not been done until recently. The Great Chaco is very important as the unique dry subtropical forest of the earth, but it is suffering increasing degradation by the advance of agriculture. Spider communities have been shown to be more directly influenced by vegetation architecture than vegetation species composition. In this study, we aim to assess whether spider diversity and assemblages change in adjacent habitats with different types of vegetation. We compare the diversity and spider assemblages in two different contiguous protected habitats (hygrophilous woodland and savannah parkland) of the Mburucuyá National Park, (Humid Chaco ecoregion). Seasonal samples were obtained using three types of sampling methods: pitfall trapping, beating, and manual litter extraction. The spider assemblages were different in the studied areas, and the abundance, diversity, evenness, and species richness were higher in the hygrophilous woodland than the savannah parkland. These differences in spider diversity and assemblages indicate that both types of habitats are important if the biodiversity is to be conserved in the Chaco ecoregion, where different types of habitat are shown as a patchy distribution.

Spiders are a megadiverse group that can be useful indicators of the overall species richness and health of biotic communities. The spider diversity in subtropical forests of the Neotropical region are not yet well known, especially in Argentinean subtropical forests where systematic fieldwork has not been done until recently. The Great Chaco is very important as the unique dry subtropical forest of the earth, but it is suffering increasing degradation by the advance of agriculture. Spider communities have been shown to be more directly influenced by vegetation architecture than vegetation species composition. In this study, we aim to assess whether spider diversity and assemblages change in adjacent habitats with different types of vegetation. We compare the diversity and spider assemblages in two different contiguous protected habitats (hygrophilous woodland and savannah parkland) of the Mburucuyá National Park, (Humid Chaco ecoregion). Seasonal samples were obtained using three types of sampling methods: pitfall trapping, beating, and manual litter extraction. The spider assemblages were different in the studied areas, and the abundance, diversity, evenness, and species richness were higher in the hygrophilous woodland than the savannah parkland. These differences in spider diversity and assemblages indicate that both types of habitats are important if the biodiversity is to be conserved in the Chaco ecoregion, where different types of habitat are shown as a patchy distribution.

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Sympolymnia, a new genus of myrmecomorph jumping spider belonging to the tribe Simonellini Peckham, Peckham & Wheeler, 1889, is described. It comprises five species: the type species, Sympolymnia lucasi (Taczanowski, 1871), comb. nov., Sympolymnia lauretta (Peckham & Peckham, 1892), comb. nov., Sympolymnia edwardsi (Cutler, 1985), comb. nov. and Sympolymnia shinahotasp. nov. and S. cutlerisp. nov.Sympolymnia lauretta (Peckham & Peckham, 1892) is recorded from Bolivia for the first time. Ontogenetic shifts of ant-resemblance are observed: Juveniles of S. cutlerisp. nov. and S. lauretta mimic black ants of the genus Crematogaster Lund, 1831, but those of S. shinahotasp. nov. most closely resemble Pseudomyrmex ethicus (Forel, 1911). Adults of S. cutlerisp. nov., S. lauretta and S. shinahotasp. nov. resemble the ant Camponotus sanctaefidei Dalla Torre, 1892 and orange adults of S. shinahotasp. nov. are putative mimics of Camponotus latangulus Roger, 1863.

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RESUMENSe estudia la diversidad de arañas de vegetación de las yungas del noroeste argentino, integrando dos escalas: local (diversidad α, estructura de comunidades) y su proyección a diversidad regional (diversidad β). Se muestrearon 26 sitios en la provincia de Salta, representando diferentes ambientes/pisos altitudinales de yungas sensu stricto (SP= selva pedemontana, SM= selva montana, BM= bosque montano), yungas sensu lato (Cc-s= conectividad entre centro y sur de yungas, YT= yungas en transición) y sitios de Chaco Serrano (ChS) como contraste. Se realizaron muestreos estacionales durante un año, tomando 10 muestras con G-Vac (aspirador entomológico) sobre vegetación. Se obtuvo un total de 6412 ejemplares, representando 188 especies y 34 familias (sólo yungas). Theridiidae, Anyphaenidae y Linyphiidae fueron dominantes. La mayor riqueza correspondió a Araneidae, Salticidae y Theridiidae. Especies dominantes fueron Chibchea salta (Pholcidae), Dubiaranea msp111 (Linyphiidae) y Mysmena msp110 (Mysmenidae). Diferencias relevantes en composición y abundancia separan dos grupos de ambientes: (Cc-s+SP+YT+ChS) vs. (SM+BM). Dictynidae, Oxyopidae y Philodromidae se asocian a pisos de menor altitud (Cc-s, YT, ChS). Los ambientes SP y YT contienen la mayor riqueza específica y diversidad, mientras que SM y BM presentaron la mayor similitud. En Cc-s y ChS se observaron las mayores diferencias con los demás ambientes, excepto SP. La complementariedad y coeficientes e índices de similitud revelaron alta diversidad β en la región. En consecuencia, se sugiere que además de reforzar la protección en los pisos transicionales de yungas (hábitats más deteriorados y diversos para las arañas), la gestión de conservación debería estar orientada en toda el área a promover la heterogeneidad espacial natural de las Yungas, haciendo especial hincapié en el mosaico de hábitats que constituyen cada estrato diferente.Palabras clave: Araneae; diversidad de arañas; ecología de comunidades; Yungas. ABSTRACT Spider diversification (Araneae, Araneomorphae) in mountain rainforest: a case study in the Argentine YungasThe spider diversity from yungas vegetation in northwestern Argentina is studied, integrating two levels: local (α diversity, community structures) and a projection at regional level of diversity (β diversity). Twenty six sites in Salta Province were sampled, representing different ambient/altitudinal strata of yungas sensu stricto (SP= pedemontane rainforest, SM= montane rainforest and BM= montane forest), yungas sensu lato (Cc-s= yungas central and southern sectors connectivity areas, YT= transitional yungas), and Chaco Serrano sites (ChS) as contrast. The sampling was carried out seasonally for one year taking 10 samples of vegetation with G-Vac method. A total of 6412 spiders, 188 species and 34 families were obtained (only yungas). Theridiidae, Anyphaenidae and Linyphiidae were dominant. The highest richness was observed in Araneidae, Salticidae and Theridiidae. Chibchea salta (Pholcidae), Dubiaranea msp111 (Linyphiidae) and My...