On the relative importance of space and environment in farmland bird community assembly
Résumé
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.
Domaines
Sciences de l'environnement
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