2017 |
Bender, M. G., et al. "Isolation drives taxonomic and functional nestedness in tropical reef fish faunas." Ecography. 40.3 (2017): 425–435.
Résumé: Taxonomic nestedness, the degree to which the taxonomic composition of species-poor assemblages represents a subset of richer sites, commonly occurs in habitat fragments and islands differing in size and isolation from a source pool. However, species are not ecologically equivalent and the extent to which nestedness is observed in terms of functional trait composition of assemblages still remains poorly known. Here, using an extensive database on the functional traits and the distributions of 6316 tropical reef fish species across 169 sites, we assessed the levels of taxonomical vs functional nestedness of reef fish assemblages at the global scale. Functional nestedness was considerably more common than taxonomic nestedness, and generally associated with geographical isolation, where nested subsets are gradually more isolated from surrounding reef areas and from the center of biodiversity. Because a nested pattern in functional composition implies that certain combinations of traits may be represented by few species, we identified these groups of low redundancy that include large herbivore-detritivores and omnivores, small piscivores, and macro-algal herbivores. The identified patterns of nestedness may be an outcome of the interaction between species dispersal capabilities, resource requirements, and gradients of isolation among habitats. The importance of isolation in generating the observed pattern of functional nestedness within biogeographic regions may indicate that disturbance in depauperate and isolated sites can have disproportionate effects on the functional structure of their reef fish assemblages.
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Loiseau, N., et al. "Performance of partitioning functional beta-diversity indices: Influence of functional representation and partitioning methods." Global Ecol. Biogeogr.. 26.6 (2017): 753–762.
Résumé: Aim Two frameworks (BASVIL and PODCAR), based on two different functional representations (ordination and dendrogram), have been proposed for partitioning overall functional beta diversity into two analogous components: turnover and nestedness-resultant dissimilarity, or replacement and difference of functional richness, respectively. We compared the two frameworks by testing the influence of functional representations and partitioning methods on the measurement of overall functional beta diversity and its components. Innovation We computed beta-diversity indices from the two frameworks on a set of communities simulated according to five scenarios of assembly: random, richness gradient, pure nestedness, pure turnover and mixed turnover/loss scenarios. To disentangle the effects of the partitioning approach and those of the functional representation on measurement of functional beta diversity, we also computed PODCAR indices in multidimensional space. Main conclusions BASVIL and PODCAR frameworks led to different results for overall functional beta diversity and their analogous partitioning components. Most of the difference between the two frameworks was due to the functional representation used. The goodness-of-fit measure (mean squared deviation, mSD) to assess the quality of functional spaces showed that the one computed on the basis of the dendrogram used in PODCAR remained lower than that of the functional ordination considered in BASVIL. In addition, only functional turnover derived from the BASVIL framework is independent of difference in functional richness. Finally, BASVIL measured functional variations derived from nested phenomena while PODCAR did not allow separation of this variation derived from richness difference. However, the sensitivity of BASVIL to functionally extreme species may make it difficult to know whether variations of the nestedness-resultant dissimilarity components are due to a turnover with few extreme species or a loss in functional richness. Particular attention with regard to the properties of the two frameworks is required before drawing conclusions regarding processes that structure communities.
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2014 |
Pellissier, L., et al. "Quaternary coral reef refugia preserved fish diversity." Science. 344.6187 (2014): 1016–1019.
Résumé: The most prominent pattern in global marine biogeography is the biodiversity peak in the Indo-Australian Archipelago. Yet the processes that underpin this pattern are still actively debated. By reconstructing global marine paleoenvironments over the past 3 million years on the basis of sediment cores, we assessed the extent to which Quaternary climate fluctuations can explain global variation in current reef fish richness. Comparing global historical coral reef habitat availability with the present-day distribution of 6316 reef fish species, we find that distance from stable coral reef habitats during historical periods of habitat loss explains 62% of the variation in fish richness, outweighing present-day environmental factors. Our results highlight the importance of habitat persistence during periods of climate change for preserving marine biodiversity.
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