title: Environmental and spatial drivers of taxonomic, functional, and phylogenetic characteristics of bat communities in human-modified landscapes.
abstract: BACKGROUND
  Assembly of species into communities following human disturbance (e.g., deforestation, fragmentation) may be governed by spatial (e.g., dispersal) or environmental (e.g., niche partitioning) mechanisms. Variation partitioning has been used to broadly disentangle spatial and environmental mechanisms, and approaches utilizing functional and phylogenetic characteristics of communities have been implemented to determine the relative importance of particular environmental (or niche-based) mechanisms. Nonetheless, few studies have integrated these quantitative approaches to comprehensively assess the relative importance of particular structuring processes.
  
  
  METHODS
  We employed a novel variation partitioning approach to evaluate the relative importance of particular spatial and environmental drivers of taxonomic, functional, and phylogenetic aspects of bat communities in a human-modified landscape in Costa Rica. Specifically, we estimated the amount of variation in species composition (taxonomic structure) and in two aspects of functional and phylogenetic structure (i.e., composition and dispersion) along a forest loss and fragmentation gradient that are uniquely explained by landscape characteristics (i.e., environment) or space to assess the importance of competing mechanisms.
  
  
  RESULTS
  The unique effects of space on taxonomic, functional and phylogenetic structure were consistently small. In contrast, landscape characteristics (i.e., environment) played an appreciable role in structuring bat communities. Spatially-structured landscape characteristics explained 84% of the variation in functional or phylogenetic dispersion, and the unique effects of landscape characteristics significantly explained 14% of the variation in species composition. Furthermore, variation in bat community structure was primarily due to differences in dispersion of species within functional or phylogenetic space along the gradient, rather than due to differences in functional or phylogenetic composition.
  
  
  CONCLUSIONS
  Variation among bat communities was related to environmental mechanisms, especially niche-based (i.e., environmental) processes, rather than spatial mechanisms. High variation in functional or phylogenetic dispersion, as opposed to functional or phylogenetic composition, suggests that loss or gain of niche space is driving the progressive loss or gain of species with particular traits from communities along the human-modified gradient. Thus, environmental characteristics associated with landscape structure influence functional or phylogenetic aspects of bat communities by effectively altering the ways in which species partition niche space.
authors.affiliation: Department of Natural Resources and the Environment, University of Connecticut , Storrs , CT , United States.
authors.forename: Laura M
authors.initials: LM
authors.lastname: Cisneros
authors.affiliation: Department of Geography and Environmental Systems, University of Maryland Baltimore County , Baltimore , MD , United States.
authors.forename: Matthew E
authors.initials: ME
authors.lastname: Fagan
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, United States; Center for Environmental Science and Engineering, University of Connecticut, Storrs, CT, United States.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Willig
keywords: Chiroptera; Environmental control; Forest loss; Fragmentation; Land conversion; Neotropics; Niche partitioning; Spatial mechanisms; Variation partitioning