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Barnagaud, J. - Y., Kissling, W. D., Tsirogiannis, C., Fisikopoulos, V., Villeger, S., Sekercioglu, C. H., et al. (2017). Biogeographical, environmental and anthropogenic determinants of global patterns in bird taxonomic and trait turnover. Glob. Ecol. Biogeogr., 26(10), 1190–1200.
Résumé: AimTo assess contemporary and historical determinants of taxonomic and ecological trait turnover in birds worldwide. We tested whether taxonomic and trait turnover (1) are structured by regional bioclimatic conditions, (2) increase in relationship with topographic heterogeneity and environmental turnover and change according to current and historical environmental conditions, and (3) decrease with human impact. Major TaxaBirds. LocationGlobal. MethodsWe used computationally efficient algorithms to map the taxonomic and trait turnover of 8,040 terrestrial bird assemblages worldwide, based on a grid with 110km x 110 km resolution overlaid on the extent-of-occurrence maps of 7,964 bird species, and nine ecological traits reflecting six key aspects of bird ecology (diet, habitat use, thermal preference, migration, dispersal and body size). We used quantile regression and model selection to quantify the influence of biomes, environment (temperature, precipitation, altitudinal range, net primary productivity, Quaternary temperature and precipitation change) and human impact (human influence index) on bird turnover. ResultsBird taxonomic and trait turnover were highest in the north African deserts and boreal biomes. In the tropics, taxonomic turnover tended to be higher, but trait turnover was lower than in other biomes. Taxonomic and trait turnover exhibited markedly different or even opposing relationships with climatic and topographic gradients, but at their upper quantiles both types of turnover decreased with increasing human influence. Main conclusionsThe influence of regional, environmental and anthropogenic factors differ between bird taxonomic and trait turnover, consistent with an imprint of niche conservatism, environmental filtering and topographic barriers on bird regional assemblages. Human influence on these patterns is pervasive and demonstrates global biotic homogenization at a macroecological scale.
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Buisson, L., Grenouillet, G., Villeger, S., Canal, J., & Laffaille, P. (2013). Toward a loss of functional diversity in stream fish assemblages under climate change. Glob. Change Biol., 19(2), 387–400.
Résumé: The assessment of climate change impacts on biodiversity has so far been biased toward the taxonomic identification of the species likely either to benefit from climate modifications or to experience overall declines. There have still been few studies intended to correlate the characteristics of species to their sensitivity to climate change, even though it is now recognized that functional trait-based approaches are promising tools for addressing challenges related to global changes. In this study, two functional indices (originality and uniqueness) were first measured for 35 fish species occurring in French streams. They were then combined to projections of range shifts in response to climate change derived from species distribution models. We set out to investigate: (1) the relationship between the degrees of originality and uniqueness of fish species, and their projected response to future climate change; and (2) the consequences of individual responses of species for the functional diversity of fish assemblages. After accounting for phylogenetic relatedness among species, we have demonstrated that the two indices used measure two complementary facets of the position of fish species in a functional space. We have also rejected the hypothesis that the most original and/or less redundant species would necessarily experience the greatest declines in habitat suitability as a result of climate change. However, individual species range shifts could lead simultaneously both to a severe decline in the functional diversity of fish assemblages, and to an increase in the functional similarity among assemblages, supporting the hypothesis that disturbance favors communities with combination of common traits and biotic homogenization as well. Our findings therefore emphasize the importance of going beyond the simple taxonomic description of diversity to provide a better assessment of the likely future effects of environmental changes on biodiversity, thus helping to design more effective conservation and management measures.
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Cheng, L., Blanchet, S., Loot, G., Villeger, S., Zhang, T., Lek, S., et al. (2014). Temporal changes in the taxonomic and functional diversity of fish communities in shallow Chinese lakes: the effects of river–lake connections and aquaculture. Aquatic Conservation: Marine and Freshwater Ecosystems, 24(1), 23–34.
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McLean, M., Mouillot, D., Lindegren, M., Villeger, S., Engelhard, G., Murgier, J., et al. (2019). Fish communities diverge in species but converge in traits over three decades of warming. Glob. Change Biol., 25(11), 3972–3984.
Résumé: Describing the spatial and temporal dynamics of communities is essential for understanding the impacts of global environmental change on biodiversity and ecosystem functioning. Trait-based approaches can provide better insight than species-based (i.e. taxonomic) approaches into community assembly and ecosystem functioning, but comparing species and trait dynamics may reveal important patterns for understanding community responses to environmental change. Here, we used a 33-year database of fish monitoring to compare the spatio-temporal dynamics of taxonomic and trait structure in North Sea fish communities. We found that the majority of variation in both taxonomic and trait structure was explained by a pronounced spatial gradient, with distinct communities in the southern and northern North Sea related to depth, sea surface temperature, salinity and bed shear stress. Both taxonomic and trait structure changed significantly over time; however taxonomically, communities in the south and north diverged towards different species, becoming more dissimilar over time, yet they converged towards the same traits regardless of species differences. In particular, communities shifted towards smaller, faster growing species with higher thermal preferences and pelagic water column position. Although taxonomic structure changed over time, its spatial distribution remained relatively stable, whereas in trait structure, the southern zone of the North Sea shifted northward and expanded, leading to homogenization. Our findings suggest that global environmental change, notably climate warming, will lead to convergence towards traits more adapted for novel environments regardless of species composition.
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Toussaint, A., Beauchard, O., Oberdorff, T., Brosse, S., & Villeger, S. (2016). Worldwide freshwater fish homogenization is driven by a few widespread non-native species. Biol. Invasions, 18(5), 1295–1304.
Résumé: Introduction of non-native species have changed the composition of freshwater fish assemblages throughout the world and hence the dissimilarity between them, either toward homogenization (i.e. decrease in dissimilarity) or differentiation (i.e. increase in dissimilarity). However, there is still no assessment of individual contributions of non-native species to this overall trend at the global scale. Here, we disentangle individual non-native species effect from the global effect of the whole introduced species pool at the biogeographic realm scale and test which determinant can explain the effect of non-native species on changes in assemblage dissimilarity. Our results show that the contribution of introduced species on changes in dissimilarity is highly variable and all directions of changes are observed through the introduction process, i.e. either toward homogenization, differentiation or no change. Overall, only a few widespread species contribute to the worldwide homogenization pattern, whereas most of introduced species slightly contribute to the global change in dissimilarity. The effect of species on change in dissimilarity was influenced by the introduction pressure but also by whether introduced species were translocated (i.e. introduced to other basins within their biogeographic realm) or exotic (i.e. introduced from other biogeographic realms). Homogenization is strongly determined by the species translocated within a realm and only by few widespread exotic species whereas the majority of exotics contribute to a differentiation effect. Nevertheless, under future intensified human pressure, the exotic species spread across realms is predicted to increase and their differentiation effect might turn towards homogenization, and might trigger the global homogenization trend.
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