Abstract
The relative contribution of ecological processes in shaping metacommunity dynamics in heavily managed landscapes is still unclear. Here we used two complementary approaches to disentangle the role of environment and spatial effect in farmland bird community assembly in an intensive agro-ecosystem. We hypothesized that the interaction between habitat patches and dispersal should play a major role in such unstable and unpredictable environments. First, we used a metacommunity patterns analysis to characterize species co-occurrences and identify the main drivers of community assembly; secondly, variation partitioning was used to disentangle environmental and geographical factors (such as dispersal limitation) on community structure and composition. We used high spatial resolution data on bird community structure and composition distributed among 260 plots in an agricultural landscape. Species were partitioned into functional classes, and point count stations were classified according to landscape characteristics before applying metacommunity and partitioning analyses within each. Overall we could explain around 20% of the variance in species composition in our system, revealing that stochasticity remains very important at this scale. However, this proportion varies depending on the scale of analysis, and reveals potentially important contributions of environmental filtering and dispersal. These conclusions are further reinforced when the analysis was deconstructed by bird functional classes or by landscape habitat classes, underlining trait-related filters, thus reinforcing the idea that wooded areas in these agroecosystems may represent important sources for a specific group of bird species. Our analysis shows that deconstructing the species assemblages into separate functional groups and types of landscapes, along with a combination of analysis strategies, can help in understanding the mechanisms driving community assembly.
Highlights
Understanding the mechanisms involved in community assembly is a major challenge for ecologists
Recent studies have suggested that models including spatial autocorrelation due to dispersal, as well as stochastic events of colonization and extinction, can better represent metacommunity structure and species distribution ranges as compared to models based on environmental variation only [9,10]
The study of the spatial structure of community composition is useful in disentangling community drivers, but it is not sufficient to distinguish between mechanisms driving community assembly
Summary
Understanding the mechanisms involved in community assembly is a major challenge for ecologists. Meta-community theory suggests that the composition of a community results from four kinds of mechanisms: biotic interactions, environmental filtering, dispersal and demographic stochasticity [1,2,3]. Other mechanisms that can generate spatial autocorrelation include population dynamics (reproduction and mortality), local dispersal [7], and environmental filtering [8]. Recent studies have suggested that models including spatial autocorrelation due to dispersal, as well as stochastic events of colonization and extinction, can better represent metacommunity structure and species distribution ranges as compared to models based on environmental variation only [9,10]. The study of the spatial structure of community composition is useful in disentangling community drivers, but it is not sufficient to distinguish between mechanisms driving community assembly
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