Worldwide decline of specialist species: toward a global functional homogenization?

Clavel, Joanne; Julliard, Romain; Devictor, Vincent

doi:10.1890/080216

Cited by 1,147 publications

(1,090 citation statements)

References 55 publications

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“…Thus, our study shows that several mechanisms determine community composition and functioning at the same time, and is in congruence with previous studies showing that species sorting and neutral processes have simultaneous roles during community assembly (Ofiteru et al, 2010;Langenheder and Székely, 2011). Moreover, environmental changes are prone to increase the abundance of generalists (Clavel et al, 2011), and also the adjustment scenario (Comte and del Giorgio, 2011) predicts a conversion towards generalists upon exposure to new environmental conditions. The fact that this was not observed here (Supplementary Table S3) might indicate that complex interactions within communities are more important in defining environmental affinities of taxa than abiotic conditions.…”

Section: Fate Of Dispersed Bacterial Communitiessupporting

confidence: 91%

Mechanisms determining the fate of dispersed bacterial communities in new environments

2012

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Recent work has shown that dispersal has an important role in shaping microbial communities. However, little is known about how dispersed bacteria cope with new environmental conditions and how they compete with local resident communities. To test this, we implemented two full-factorial transplant experiments with bacterial communities originating from two sources (freshwater or saline water), which were incubated, separately or in mixes, under both environmental conditions. Thus, we were able to separately test for the effects of the new environment with and without interactions with local communities. We determined community composition using 454-pyrosequencing of bacterial 16S rRNA to specifically target the active fraction of the communities, and measured several functional parameters. In absence of a local resident community, the net functional response was mainly affected by the environmental conditions, suggesting successful functional adaptation to the new environmental conditions. Community composition was influenced both by the source and the incubation environment, suggesting simultaneous effects of species sorting and functional plasticity. In presence of a local resident community, functional parameters were higher compared with those expected from proportional mixes of the unmixed communities in three out of four cases. This was accompanied by an increase in the relative abundance of generalists, suggesting that competitive interactions among local and immigrant taxa could explain the observed 'functional overachievement'. In summary, our results suggest that environmental filtering, functional plasticity and competition are all important mechanisms influencing the fate of dispersed communities.

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Section: Fate Of Dispersed Bacterial Communitiessupporting

confidence: 91%

Mechanisms determining the fate of dispersed bacterial communities in new environments

2012

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“…into elevated niche differentiation and specialisation, and therefore into higher diversity but lower functional redundancy (Rosenfeld, 2002;Clavel et al, 2011). The notion that the metabolism of diverse DOC may be related to microbial diversity agrees, in fact, with theory of niche partitioning among competing species (Rosenfeld, 2002;Kassen, 2002;Evans et al, 2005), whereas our findings on functional redundancy do not fully agree with our expectations.…”

Section: Discussioncontrasting

confidence: 62%

“…In fact, dispersal limitation is commonly believed to be higher in the headwater reaches (Besemer et al, 2013), which would induce stronger constraints on the colonisation dynamics of microbial specialists. Furthermore, the combination of elevated physical disturbance (e.g., hydrology) on microbial communities (Widder et al, 2014) upstream with the observation that postdisturbance recovery of specialists is less successful than for generalists (Clavel et al, 2011) may further contribute to the spatial patterns of functional traits we observed in this study. Finally, benthic algae which provide the bulk DOC source in streams above the treeline exude compounds, often monomeric in nature, that do not require specialised metabolic pathways and that are therefore readily available to a wide range of microbial heterotrophs (Kaplan and Bott, 1989).…”

Section: Discussionmentioning

confidence: 67%

Altitudinal patterns of diversity and functional traits of metabolically active microorganisms in stream biofilms

et al. 2015

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Resources structure ecological communities and potentially link biodiversity to energy flow. It is commonly believed that functional traits (generalists versus specialists) involved in the exploitation of resources depend on resource availability and environmental fluctuations. The longitudinal nature of stream ecosystems provides changing resources to stream biota with yet unknown effects on microbial functional traits and community structure. We investigated the impact of autochthonous (algal extract) and allochthonous (spruce extract) resources, as they change along alpine streams from above to below the treeline, on microbial diversity, community composition and functions of benthic biofilms. Combining bromodeoxyuridine labelling and 454 pyrosequencing, we showed that diversity was lower upstream than downstream of the treeline and that community composition changed along the altitudinal gradient. We also found that, especially for allochthonous resources, specialisation by biofilm bacteria increased along that same gradient. Our results suggest that in streams below the treeline biofilm diversity, specialisation and functioning are associated with increasing niche differentiation as potentially modulated by divers allochthonous and autochthonous constituents contributing to resources. These findings expand our current understanding on biofilm structure and function in alpine streams.

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“…Many of these only use a proxy for functional homogenization, that is, mean community specialization. This method assumes that generalist species colonize an area and outcompete specialist species, thus decreasing the mean specialization of the community (Clavel, Julliard & Devictor, 2011; Davey, Chamberlain, Newson, Noble & Johnston, 2012). Using mean specialization, however, ignores similarity between communities (Gosselin, 2012), which is integral to the general definition of homogenization as an increase in spatial similarity of genetic, functional, or taxonomic diversity in time (Olden & Rooney, 2006; Olden et al., 2004).…”

Section: Introductionmentioning

confidence: 99%

Does functional homogenization accompany taxonomic homogenization of British birds and how do biotic factors and climate affect these processes?

White

Montgomery

Storchová

et al. 2018

Ecology and Evolution

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Environmental change has reshuffled communities often causing taxonomic homogenization rather than differentiation. Some studies suggest that this increasing similarity of species composition between communities is accompanied by an increase in similarity of trait composition—functional homogenization—although different methodologies have failed to come to any consistent conclusions. Functional homogenization could have a large effect on ecosystem functioning and stability. Here, we use the general definition of homogenization as “reduced spatial turnover over time” to compare changes in Simpson's beta diversity (taxonomic turnover) with changes in Rao's quadratic entropy beta diversity (functional turnover) in British breeding birds at three spatial scales. Using biotic and climatic variables, we identify which factors may predispose a site to homogenization. The change in turnover measures between two time periods, 20 years apart, was calculated. A null model approach was taken to identify occurrences of functional homogenization and differentiation independent of changes in taxonomic turnover. We used conditional autoregressive models fitted using integrated nested Laplace approximations to determine how environmental drivers and factors relating to species distributions affect changes in spatial turnover of species and functional diversity. The measurement of functional homogenization affects the chance of rejection of the null models, with many sites showing taxonomic homogenization unaccompanied by functional homogenization, although occurrence varies with spatial scale. At the smallest scale, while temperature‐related variables drive changes in taxonomic turnover, changes in functional turnover are associated with variation in growing degree days; however, changes in functional turnover become more difficult to predict at larger spatial scales. Our results highlight the multifactorial processes underlying taxonomic and functional homogenization and that redundancy in species traits may allow ecosystem functioning to be maintained in some areas despite changes in species composition.

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Worldwide decline of specialist species: toward a global functional homogenization?

Cited by 1,147 publications

References 55 publications

Mechanisms determining the fate of dispersed bacterial communities in new environments

Mechanisms determining the fate of dispersed bacterial communities in new environments

Altitudinal patterns of diversity and functional traits of metabolically active microorganisms in stream biofilms

Does functional homogenization accompany taxonomic homogenization of British birds and how do biotic factors and climate affect these processes?

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