ABSTRACT. The Araneidae is a speciose family including web-spinning spiders that are very abundant in various terrestrial ecosystems. Several studies demonstrate that changes in vegetation surrounding rivers, streams and brooks affect the associated araneofauna. The aim of this research was to compare differences found in diversity (abundance and richness), composition and phenology of Araneidae spiders sampled in different habitats in four riparian forest catchments in southern Brazil. Samples were taken from riparian forests in four rivers of Rio Grande do Sul State: Piratini, Camaquã, Sinos and Maquiné rivers, each in a different hydrographic basin. Samples were taken twice seasonally on each basin during two years, sampling the araneofauna of the tree-shrub strata with beating tray. Six transects were employed on each basin, two per habitat: edge with grassland, forest interior and river edge. Araneids totalled 20 genera and 65 species. Comparing riparian forests significant differences are found. Spider abundance differed among riparian forests as well as species richness. Overall, Piratini river riparian forest had the higher abundance and richness for Araneidae; the lower values were in Sinos river forest. The stronger degradation and fragmentation of the riparian forests of Sinos river probably influenced the results, with human disturbance gradients associated negatively to web building. We present data on the diversity of these spiders, which were very abundant in the riparian forest interior and very rich in species in the grassland/riparian forest edge. Species composition also differs among the studied habitats (the above plus river/riparian forest edge). For the most abundant species the phenological pattern across the seasons was also analysed.KEYWORDS. Spiders, habitats, Rio Grande do Sul, abundance, richness.RESUMO. Diversidade, composição e fenologia de aranhas construtoras de teias (Araneae, Araneidae) associadas com matas ciliares no sul do Brasil. Araneidae é uma das famílias com maior número de espécies, incluindo aranhas construtoras de teias que são muito abundantes em diversos ecossistemas terrestres. Vários estudos demonstram que mudanças na vegetação circundante de rios, córregos e riachos pode afetar a araneofauna associada. O objetivo deste estudo foi avaliar aspectos sobre a diversidade (abundância e riqueza), composição e fenologia de aranhas Araneidae foram amostradas em diferentes habitats em quatro bacias de mata ciliar no sul do Brasil. Foram coletadas amostras de matas ciliares em quatro rios do Rio Grande do Sul, todos em diferentes bacias hidrográficas: nos rios Piratini, Camaquã, dos Sinos e Maquiné. As amostras foram realizadas duas vezes por estação em cada bacia, durante dois anos, a amostragem da araneofauna do estrato arbóreo-arbustivo foi realizada com guardachuva entomológico. Seis transecções foram empregadas em cada mata ciliar, dois por habitat: borda com campo, interior da floresta e borda do rio. Araneídeos totalizaram 20 gêneros e 65 espécies. Comparando-se as ...

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The fact that spiders are widely distributed in terrestrial ecosystems makes them efficient organisms to help elucidate biodiversity patterns (Uetz 1991, Foelix 1996, Platnick 1999, cardoso 2009). In order to know and to catalogue the biodiversity elements of a given place, however, it is necessary to conduct biodiversity surveys (dennis & rUggiero 1996). Such inventories should not be restricted to a list of species, but need to include information on systematics, ecology, and biogeography (HalFFter et al. 2001). Among the environments where spiders have already been inventoried, riparian forests are still largely unknown (rodrigUes et al. 2014). These habitats have important ecosystem functions, since they are ecotones between adjacent environments and therefore harbor a diverse fauna (naiman et al. 1993). Riparian forests are peculiar: they occupy a small proportion of the hydrographic basin they belong to, are considered ecologically stable and are well defined, have high plant biomass production and support high biodiversity levels compared to other forest environments (davide & BotelHo 1999). They are considered extremely important for plant dispersal, and as "corridors" for animal movement (naiman et al. 1993, malavasi et al. 2004), including spiders (raizer et al. 2005, rodrigUes et al. 2014). However, these corridors may be interrupted when plant formations are altered. In the past, Brazilian native riparian forests were partly substituted for large plantations of exotic trees and, very close to rivers, by agricultural endeavors, a process that has resulted in numerous forest remnants and semi-natural areas (dennis 1997, malavasi et al. 2004).

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Until now no species of Rhinocricus have been described or registered for the state of Rio Grande do Sul, Brazil. In thiswork we describe and illustrate five new species of Rhinocricus from Rio Grande do Sul: R. itauba sp. nov., R. gauchussp. nov., R. guaritas sp. nov., and R. serranus sp. nov., described from specimens of both sexes, and R. vacariensis sp. nov.based on a single male. The species R. divaricatus, R. padbergi and R. serratus are registered for the first time for this state. A key to Rio Grande do Sul species is presented.

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