title: Metacommunity composition of web-spiders in a fragmented neotropical forest: relative importance of environmental and spatial effects.
abstract: The distribution of beta diversity is shaped by factors linked to environmental and spatial control. The relative importance of both processes in structuring spider metacommunities has not yet been investigated in the Atlantic Forest. The variance explained by purely environmental, spatially structured environmental, and purely spatial components was compared for a metacommunity of web spiders. The study was carried out in 16 patches of Atlantic Forest in southern Brazil. Field work was done in one landscape mosaic representing a slight gradient of urbanization. Environmental variables encompassed plot- and patch-level measurements and a climatic matrix, while principal coordinates of neighbor matrices (PCNMs) acted as spatial variables. A forward selection procedure was carried out to select environmental and spatial variables influencing web-spider beta diversity. Variation partitioning was used to estimate the contribution of pure environmental and pure spatial effects and their shared influence on beta-diversity patterns, and to estimate the relative importance of selected environmental variables. Three environmental variables (bush density, land use in the surroundings of patches, and shape of patches) and two spatial variables were selected by forward selection procedures. Variation partitioning revealed that 15% of the variation of beta diversity was explained by a combination of environmental and PCNM variables. Most of this variation (12%) corresponded to pure environmental and spatially environmental structure. The data indicated that (1) spatial legacy was not important in explaining the web-spider beta diversity; (2) environmental predictors explained a significant portion of the variation in web-spider composition; (3) one-third of environmental variation was due to a spatial structure that jointly explains variation in species distributions. We were able to detect important factors related to matrix management influencing the web-spider beta-diversity patterns, which are probably linked to historical deforestation events.
authors.affiliation: Programa de Pós-Graduação em Ecologia, Departamento de Ecologia, Universidade Federal do Rio Grande do Sul-UFRGS, Porto Alegre, Rio Grande do Sul, Brazil. roneibaldissera@yahoo.com.br
authors.forename: Ronei
authors.initials: R
authors.lastname: Baldissera
authors.forename: Everton N L
authors.initials: EN
authors.lastname: Rodrigues
authors.forename: Sandra M
authors.initials: SM
authors.lastname: Hartz
mesh_terms: D000818:Animals; D044822:Biodiversity; D001938:Brazil; D017753:Ecosystem; D004777:Environment; D005843:Geography; D006790:Host-Parasite Interactions; D011157:Population Dynamics; D013037:Spatial Behavior; D013112:Spiders / Q000145:classification / Q000254:growth & development* / Q000502:physiology; D014197:Trees / Q000254:growth & development* / Q000469:parasitology; D014329:Tropical Climate