A family of null models to distinguish between environmental filtering and biotic interactions in functional diversity patterns

Chalmandrier, Loïc; Münkemüller, Tamara; Gallien, Laure; Bello, Francesco de; Mazel, Florent; Lavergne, Sébastien; Thuiller, Wilfried

doi:10.1111/jvs.12031

Cited by 64 publications

(100 citation statements)

References 54 publications

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“…We compare observed functional diversity with that of random assemblages, to assess how functional diversity varies between our focal assemblages when taking into account differences in their species richness. The spatial definition of the pool of species on which null models are based can strongly determine conclusions regarding community assembly processes (Chalmandrier et al, 2013;Herben et al, 2013). Therefore, we constructed a specific trait matrix for the regional pool of species occurring within each of our main bio-regions (the Western Palearctic, North America and South America).…”

Section: Functional Diversity Metricsmentioning

confidence: 99%

Impacts of Urban Areas and Their Characteristics on Avian Functional Diversity

Hagen

Ibáñez‐Álamo

et al. 2017

Front. Ecol. Evol.

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Urban development is rapidly expanding across the globe and is a major driver of environmental change. Despite considerable improvements in our understanding of how species richness responds to urbanization, there is still insufficient knowledge of how other measures of assemblage composition and structure respond to urban development. Functional diversity metrics provide a useful approach for quantifying ecological function. We compare avian functional diversity in 25 urban areas, located across the globe, with paired non-urban assemblages using a database of 27 functional traits that capture variation in resource use (amount and type of resources and how they are acquired) across the 529 species occurring across these assemblages. Using three standard functional diversity metrics (FD, MNTD, and convex hull) we quantify observed functional diversity and, using standardized effect sizes, how this diverges from that expected under random community assembly null models. We use regression trees to investigate whether human population density, amount of vegetation and city size (spatial extent of urban land), bio-region and use of semi-natural or agricultural assemblages as a baseline modulate the effect of urbanization on functional diversity. Our analyses suggest that observed functional diversity of urban avian assemblages is not consistently different from that of non-urban assemblages. After accounting for species richness avian functional diversity is higher in cities than areas of semi-natural habitat. This creates a paradox as species responses to urban development are determined by their ecological traits, which should generate assemblages clustered within a narrow range of trait space. Greater habitat diversity within cities compared to semi-natural areas dominated by a single habitat may enhance functional diversity in cities and explain this paradox. Regression trees further suggest that smaller urban areas, lower human population densities and increased vegetation all enhance the functional diversity of urban areas. A city's attributes can thus influence the functional diversity of its biological assemblages, and their associated ecological functions. This has important implications for the debate regarding how we should grow the world's cities whilst maintaining their ecological function.

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Section: Functional Diversity Metricsmentioning

confidence: 99%

Impacts of Urban Areas and Their Characteristics on Avian Functional Diversity

Hagen

Ibáñez‐Álamo

et al. 2017

Front. Ecol. Evol.

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“…Functional evenness and dispersion are independent from species richness, which allows comparison of quadrats and ontogenetic stages with different species richness without bias, and their independence from functional richness allows for testing of differences in functional evenness or dispersion with different functional richness values (laliberte and legendre 2010; Villeger et al 2008). Co-occurring species tend to be functionally convergent under strong environmental filtering (Chalmandrier et al 2013;Cornwell et al 2006;spasojevic and suding 2012). We expected that functional similarity would increase from saplings to large trees.…”

Section: Functional Traitsmentioning

confidence: 99%

Determinants of change in subtropical tree diameter growth with ontogenetic stage

et al. 2014

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“…Including information on absent species has improved our understanding of community assembly (de Bello et al., 2012; Chalmandrier et al., 2013) and can improve predictions of which species will establish. The accuracy of such predictions, however, is highly dependent on how dissimilarity is measured.…”

Section: Discussionmentioning

confidence: 99%

“…This requires gathering data on both regional and local diversity and identifying an appropriate habitat‐specific species pool, as in null modeling approaches (de Bello et al., 2012; Chalmandrier et al., 2013; Lessard et al., 2016). Diversity at these three scales must then be combined with information on species’ functional traits or phylogenetic relationships.…”

Section: An Overview Of the Frameworkmentioning

confidence: 99%

Predicting species establishment using absent species and functional neighborhoods

Bennett

Pärtel

2017

Ecology and Evolution

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Species establishment within a community depends on their interactions with the local environment and resident community. Such environmental and biotic filtering is frequently inferred from functional trait and phylogenetic patterns within communities; these patterns may also predict which additional species can establish. However, differentiating between environmental and biotic filtering can be challenging, which may complicate establishment predictions. Creating a habitat‐specific species pool by identifying which absent species within the region can establish in the focal habitat allows us to isolate biotic filtering by modeling dissimilarity between the observed and biotically excluded species able to pass environmental filters. Similarly, modeling the dissimilarity between the habitat‐specific species pool and the environmentally excluded species within the region can isolate local environmental filters. Combined, these models identify potentially successful phenotypes and why certain phenotypes were unsuccessful. Here, we present a framework that uses the functional dissimilarity among these groups in logistic models to predict establishment of additional species. This approach can use multivariate trait distances and phylogenetic information, but is most powerful when using individual traits and their interactions. It also requires an appropriate distance‐based dissimilarity measure, yet the two most commonly used indices, nearest neighbor (one species) and mean pairwise (all species) distances, may inaccurately predict establishment. By iteratively increasing the number of species used to measure dissimilarity, a functional neighborhood can be chosen that maximizes the detection of underlying trait patterns. We tested this framework using two seed addition experiments in calcareous grasslands. Although the functional neighborhood size that best fits the community's trait structure depended on the type of filtering considered, selecting these functional neighborhood sizes allowed our framework to predict up to 50% of the variation in actual establishment from seed. These results indicate that the proposed framework may be a powerful tool for studying and predicting species establishment.

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A family of null models to distinguish between environmental filtering and biotic interactions in functional diversity patterns

Abstract: We argue that the traditional null model approach can only identify a single main process at a time and suggest to rather use a family of null models to disentangle intertwined assembly processes acting across spatial and evolutionary scales.

Cited by 64 publications

References 54 publications

Impacts of Urban Areas and Their Characteristics on Avian Functional Diversity

Impacts of Urban Areas and Their Characteristics on Avian Functional Diversity

Determinants of change in subtropical tree diameter growth with ontogenetic stage

Predicting species establishment using absent species and functional neighborhoods

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