Landscape mosaic of Araucaria forest and forest monocultures influencing understorey spider assemblages in southern Brazil RONEI BALDISSERA, 1 * GISLENE GANADE, 2 ANTONIO D. BRESCOVIT 3 AND SANDRA M. HARTZ 1 1 Programa de Pós-Graduação em Ecologia, Federal University of Rio Grande do Sul, Laboratório de Ecologia de Populações e Comunidades, Centro de Ecologia, Porto Alegre, Rio Grande do Sul, 2 Laboratorio de Ecologia da Restauraçáo, Universidade doVale do Rio dos Sinos, São Leopoldo Rio Grande do Sul, and 3 Laboratório de Artrópodes, Instituto Butantan, São Paulo, Brazil Abstract This study investigates how abundance, diversity and composition of understorey spiders were influ- enced by four different forest habitats in a southern Brazilian Araucaria forest. The study area encompasses a landscape mosaic comprised of Araucaria forest, Araucaria plantation, Pinus plantation, and Eucalyptus plantation. Understorey spiders were collected by beating the vegetation inside three patches of each forest habitat.To assess possible predictors of spider assemblage structure, several patch features were analysed: potential prey abundances, estimation of vegetation cover, diversity index of vegetation types, patch ages, patch areas, and geographical distance between patches.To assess the influence of high-level taxa approaches on spider assemblage patterns, analyses were carried out individually for family, genera and species levels. Additionally, Mantel tests were carried out in underlying similarity matrices between each taxon. Significant differences in spider abundances among forest habitats were found. Pinus plantations showed the highest abundance of spiders and Eucalyptus plantations showed the lowest abundance. Spider abundance was significantly influenced by patch ages, geographical distance and vegetation cover. Expected numbers of families, genera and species did not vary among forest habitats. Spider composition of two Eucalyptus patches differed from the other forest patches, probably due to their low vegetation cover and isolation. Genera composition was the best correlate of species composition, showing that a higher-level surrogate can be an alternative to the species approach. The understorey spider diversity in this managed area could be maintained when suitable habitat structures are provided, thus ensuring the connectivity between different habitat types. Further studies should focus on individual species responses to the conversion of native forest to monocultures. Key words: Atlantic forest, forest management, habitat connectivity, habitat structure, tree monocultures. INTRODUCTION Studies of the effects of human modified habitats on the structure of animal communities provide essential contributions to the environmental management debate. Forest landscape structure and floristic com- position worldwide are highly determined by human activities. The management practices used on these lands will largely determine how successfully human society will conserve forest flora and fauna and maintain ecosystem health (Lindenmayer & Franklin 2002).We must therefore develop tools to gain access and predict the consequences of human actions on species diversity (Morris 2003). Human action can create a set of different habitats represented by a different number of spatially hetero- geneous patches, in effect, an environmental mosaic (Turner & Gardner 1991). This mosaic contains a set of structural features that can show a variety of species diversity patterns because different species are likely to occupy different habitats (MacArthur 1965; Rosenzweig 1995). The distribution of organisms could be determined by their capacity of dispersion and colonization, whereas the abundance of organisms within popula- tions could be affected by the taxa interactions on a local spatial scale (Cornell & Lawton 1992).Therefore, we can expect a gradient of regional/local influences *Corresponding author. R. Baldissera, Faculdade de For- mação de Professores e Especialistas em Educação, Fundação de Ensino Superior da Região Centro-Sul (FUNDASUL). Av. Cônego Luiz Walter Hanquet 151, Camaquã, Rio Grande do Sul, CEP 96180-000, Brazil (Email: roneibaldissera@yahoo. com.br) Accepted for publication January 2007. Austral Ecology (2008) 33, 45–54 © 2008 The Authors doi:10.1111/j.1442-9993.2007.01789.x Journal compilation © 2008 Ecological Society of Australia