Metacommunity Composition of Web-Spiders in a Fragmented Neotropical Forest: Relative Importance of Environmental and Spatial Effects

Sandra M. Hartz,Ronei Baldissera,Everton N. L. Rodrigues

doi:10.1371/journal.pone.0048099

Sandra M. Hartz, Ronei Baldissera + Show 1 more

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https://doi.org/10.1371/journal.pone.0048099

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Journal: PLoS ONE	Publication Date: Oct 23, 2012
Citations: 21	License type: CC BY 4.0

Affiliation: Universidade Federal do Rio Grande do Sul

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.

Highlights

The historical process of Atlantic Forest deforestation resulted in the present pattern of many forest fragments distributed in a matrix of different land uses [1], creating the possibility for nondirectional variation in metacommunity composition [2] among the network of forest remnants
Several recent studies have increased understanding of the causes and consequences of Atlantic Forest loss and fragmentation, showing that variation in arthropod species composition among fragments is affected by human disturbance, and that mosaics of native and managed forests can harbor a significant portion of arthropod diversity [1,3,4,5,6]
General Patterns We collected a total of 3854 web spiders from 16 Atlantic Forest patches

Summary

Introduction

The historical process of Atlantic Forest deforestation resulted in the present pattern of many forest fragments distributed in a matrix of different land uses [1], creating the possibility for nondirectional variation in metacommunity composition [2] among the network of forest remnants. Several recent studies have increased understanding of the causes and consequences of Atlantic Forest loss and fragmentation, showing that variation in arthropod species composition among fragments is affected by human disturbance, and that mosaics of native and managed forests can harbor a significant portion of arthropod diversity [1,3,4,5,6]. The Atlantic forest is recognized for its large number of species and high number of endemic species [7]. This biome is one of the most highly threatened tropical forests, because its deforestation has been closely related to the economic exploitation of different commodities [4]. Recently changes to the Brazilian Forestry Code proposed by Brazilian Congress may result in serious harm for the remaining Atlantic forest fragments inserted in private properties, causing the loss of biodiversity and ecosystem services [8]

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