The Experts below are selected from a list of 54561 Experts worldwide ranked by ideXlab platform
David Mouillot - One of the best experts on this subject based on the ideXlab platform.
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low functional β diversity despite high taxonomic β diversity among tropical estuarine Fish Communities
PLOS ONE, 2012Co-Authors: Sebastien Villeger, Julia Ramos Miranda, D Hernandez, David MouillotAbstract:The concept of β-diversity, defined as dissimilarity among Communities, has been widely used to investigate biodiversity patterns and community assembly rules. However, in ecosystems with high taxonomic β-diversity, due to marked environmental gradients, the level of functional β-diversity among Communities is largely overlooked while it may reveal processes shaping community structure. Here, decomposing biodiversity indices into α (local) and γ (regional) components, we estimated taxonomic and functional β-diversity among tropical estuarine Fish Communities, through space and time. We found extremely low functional β-diversity values among Fish Communities (<1.5%) despite high dissimilarity in species composition and species dominance. Additionally, in contrast to the high α and γ taxonomic diversities, α and γ functional diversities were very close to the minimal value. These patterns were caused by two dominant functional groups which maintained a similar functional structure over space and time, despite the strong dissimilarity in taxonomic structure along environmental gradients. Our findings suggest that taxonomic and functional β-diversity deserve to be quantified simultaneously since these two facets can show contrasting patterns and the differences can in turn shed light on community assembly rules.
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contrasting changes in taxonomic vs functional diversity of tropical Fish Communities after habitat degradation
Ecological Applications, 2010Co-Authors: Sebastien Villeger, Julia Ramos Miranda, D Hernandez, David MouillotAbstract:Human activities have strong impacts on ecosystem functioning through their effect on abiotic factors and on biodiversity. There is also growing evidence that species functional traits link changes in species composition and shifts in ecosystem processes. Hence, it appears to be of utmost importance to quantify modifications in the functional structure of species Communities after human disturbance in addition to changes in taxonomic structure. Despite this fact, there is still little consensus on the actual impacts of human-mediated habitat alteration on the components of biodiversity, which include species functional traits. Therefore, we studied changes in taxonomic diversity (richness and evenness), in functional diversity, and in functional specialization of estuarine Fish Communities facing drastic environmental and habitat alterations. The Terminos Lagoon (Gulf of Mexico) is a tropical estuary of primary concern for its biodiversity, its habitats, and its resource supply, which have been severely impacted by human activities. Fish Communities were sampled in four zones of the Terminos Lagoon 18 years apart (1980 and 1998). Two functions performed by Fish (food acquisition and locomotion) were studied through the measurement of 16 functional traits. Functional diversity of Fish Communities was quantified using three independent components: richness, evenness, and divergence. Additionally, we measured the degree of functional specialization in Fish Communities. We used a null model to compare the functional and the taxonomic structure of Fish Communities between 1980 and 1998. Among the four largest zones studied, three did not show strong functional changes. In the northern part of the lagoon, we found an increase in Fish richness but a significant decrease of functional divergence and functional specialization. We explain this result by a decline of specialized species (i.e., those with particular combinations of traits), while newly occurring species are redundant with those already present. The species that decreased in abundance have functional traits linked to seagrass habitats that regressed consecutively to increasing eutrophication. The paradox found in our study highlights the need for a multifaceted approach in the assessment of biodiversity changes in Communities under pressure.
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limiting similarity niche filtering and functional diversity in coastal lagoon Fish Communities
Estuarine Coastal and Shelf Science, 2007Co-Authors: David Mouillot, Olivier Dumay, Jean Antoine TomasiniAbstract:The fundamental idea behind the study of biodiversity patterns is the presumed connection between the shape of species assemblages and the functional ways in which they are organized, this functional organization referring to how species are related to one another, as competitors or members of a web of interactions and to how species are facing similar environmental constraints. Amongst the different facets of biodiversity, functional diversity is certainly a key for ecosystem processes in coastal areas. However, surprisingly, patterns of functional diversity have received little attention until now. After presenting a common framework linking functional diversity patterns to species coexistence theories, the aim of our study was twofold: (1) to seek assembly rules in brackish lagoon Fish Communities drove by functional traits. To this aim we used null models to examine the influence of two opposing forces acting on community structure: interspecific competition that might prevent the coexistence of the most similar species, and environmental filters that might result in the most similar species to coexist. (2) To seek relationships between Fish functional diversity and environmental gradients, if any. Fish sampling was carried out in two coastal lagoons where stations differ considerably in terms of physicochemical parameters. Using morphological functional traits, functional diversity of Fish Communities was estimated using two recently published indices as well as a new proposed index. Firstly our study was not able to demonstrate a limitation of similarity in coexisting lagoon Fishes due to interspecific competition. Conversely our results support the niche filtering hypothesis preventing species too dissimilar from one another to co-occur at the same station. Secondly, salinity was positively related to the functional diversity of Fishes in both lagoons suggesting that within species assemblages near the channel species are less redundant than at stations far from the channel where species tend to be functionally similar (benthic and eating zooplankton).
Songguang Xie - One of the best experts on this subject based on the ideXlab platform.
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modelling Fish Communities in relation to water quality in the impounded lakes of china s south to north water diversion project
Ecological Modelling, 2019Co-Authors: Chuanbo Guo, Yushun Chen, Han Liu, Hui Yuan, Sovan Lek, Songguang XieAbstract:Large scale inter-basin water diversion projects would have a set of ecological and environmental impacts on aquatic ecosystems. However, knowledge regarding water transfer induced water quality changes in determining Fish Communities in the impounding ecosystems remain largely unknown. In the current study, we filled this research gap by using a set of machine learning algorithms to ensemble modelling Fish community indices with water quality indicators in the impounded lakes along the eastern route of China's South-to-North Water Diversion Project (SNWDP). Overall, our results realed that water quality changes can be good predictors for the variation of Fish community structures in these lakes. Although different model techniques highlighted different variable importance of water quality in determining Fish Communities, there is generally a consensus that the hydrological related water quality indicators like: water clarity (e.g., total suspended solids) and nutrient loading (e.g., phosphate) contributed the most to the changes of Fish Communities. Our results also indicated that water diversions could bring knock-on effects on Fish Communities. Thus, more attention should be paid to long-term ecological effects from future water diversions.
Sovan Lek - One of the best experts on this subject based on the ideXlab platform.
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modelling Fish Communities in relation to water quality in the impounded lakes of china s south to north water diversion project
Ecological Modelling, 2019Co-Authors: Chuanbo Guo, Yushun Chen, Han Liu, Hui Yuan, Sovan Lek, Songguang XieAbstract:Large scale inter-basin water diversion projects would have a set of ecological and environmental impacts on aquatic ecosystems. However, knowledge regarding water transfer induced water quality changes in determining Fish Communities in the impounding ecosystems remain largely unknown. In the current study, we filled this research gap by using a set of machine learning algorithms to ensemble modelling Fish community indices with water quality indicators in the impounded lakes along the eastern route of China's South-to-North Water Diversion Project (SNWDP). Overall, our results realed that water quality changes can be good predictors for the variation of Fish community structures in these lakes. Although different model techniques highlighted different variable importance of water quality in determining Fish Communities, there is generally a consensus that the hydrological related water quality indicators like: water clarity (e.g., total suspended solids) and nutrient loading (e.g., phosphate) contributed the most to the changes of Fish Communities. Our results also indicated that water diversions could bring knock-on effects on Fish Communities. Thus, more attention should be paid to long-term ecological effects from future water diversions.
Julian D Olden - One of the best experts on this subject based on the ideXlab platform.
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revealing the pathways by which agricultural land use affects stream Fish Communities in south brazilian grasslands
Freshwater Biology, 2016Co-Authors: Renato Bolson Dalacorte, Julian D Olden, Xingli Giam, Fernando Gertum Becker, Tais De Fatima Ramos Guimaraes, Adriano S MeloAbstract:Summary Understanding mechanisms by which agricultural practices affect freshwater ecosystems helps to inform land-use policies and management strategies aimed at mitigating effects of agriculture on biodiversity. Land-use activities in the catchment, riparian and local scales likely influence stream Fish Communities via multiple pathways, for instance, by modifying the instream habitat. We investigated the mechanisms driving local stream Fish taxonomic richness and functional diversity in South Brazilian grasslands by testing a theoretical path model in which we specified a priori relationships predicting how land use at multiple scales affects instream habitat and Fish Communities. Agricultural activities adjacent to streams (i.e. local impact on the streambank) and catchment-scale cropland area were positively related to macrophyte cover and negatively associated with coarse particulate organic matter (CPOM, i.e. woody debris and leaf litter). Local impact also increased substrate siltation and homogenisation. Riparian vegetation in the upstream buffer ameliorated instream habitat condition by dampening macrophyte proliferation and providing CPOM. Fish species richness increased with both macrophyte cover and CPOM, revealing multiple pathways of agricultural influence. However, functional diversity decreased only with substrate siltation, revealing a response to agricultural activities adjacent to sample sites. Agricultural streams showed a replacement of benthic and lithophilic species by a larger number of morphologically similar and macrophyte-associated nektonic Fish. Our study indicates that land-use adjacent to streams and upstream riparian zones is critical for maintaining taxonomically and functionally diverse Fish Communities due to their strong effects on instream habitat. Protection and recovery of riparian zones from land-use change can mitigate the effects of agriculture on Fish Communities in South Brazilian grasslands.
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resource partitioning and functional diversity of worldwide freshwater Fish Communities
Ecosphere, 2016Co-Authors: Lise Comte, Julien Cucherousset, Stephanie Bouletreau, Julian D OldenAbstract:Despite significant progress in recent years, understanding the rules governing the assembly of natural Communities is still challenging and knowledge of how the integration of nonnative species may disrupt community structure and function is needed. To address this challenge, we collated stable isotope data for 159 freshwater Fish Communities around the world with and without nonnative species and quantified spatial variation in both community isotopic functional diversity and intraspecific variation in species niches. Using a null model and partial least squares path analysis, we then evaluated how the interplay between abiotic (historical, energetic, climatic, habitat size) and biotic (niche segregation) factors shape community structure and functional diversity, and how these relationships have changed, and with what consequences, in the presence of nonnative species. We found that niche partitioning is a primary force underlying the structure and functional redundancy of native Fish Communities, which may be governed by a synergism between contemporary climate, productivity and habitat size. We also found evidence of a legacy of historical climate on functional diversity, independent from species richness. By contrast, path models of Communities containing nonnative species demonstrated lower explanatory power and had no clear association with any of the abiotic or biotic factors. In conclusion, we demonstrated that strong spatial patterns in community structure and functional diversity of freshwater Fish Communities exist at the global scale, underlined by the complex interplay between external and internal filters, but that these patterns may be blurred by anthropogenic species introductions. Our results further highlighted the importance of accounting for realized species niches and species status (i.e., native and nonnative) when investigating questions related to the assembly and functional diversity of multitrophic Communities.
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Spatial isolation and Fish Communities in drainage lakes.
Oecologia, 2001Co-Authors: Julian D Olden, Donald A Jackson, Pedro R. Peres-netoAbstract:Fifty-two drainage lakes, located in south-central Ontario, Canada, were examined to study the association of isolation- and environment-related factors with Fish community composition. Eight quantitative measures of lake isolation were examined, each of which incorporated potential ecological "challenges" that a Fish encounters when moving between lakes. A Procrustean approach was employed to assess the degree of concordance between Fish assemblage structure, measures of lake isolation and environmental conditions (i.e., lake morphology and water chemistry). Our results revealed a high concordance between patterns in Fish community composition and lake isolation and lake morphology at the watershed scale, suggesting that insular and habitat-related factors influence the structure of Fish Communities. At the scale of the individual lake, this relationship varied greatly, ranging from a strong match of community composition with both spatial and abiotic conditions to Communities exhibiting weak association with these conditions. Furthermore, we showed that alternative measures of lake isolation provide additional insight into potential factors shaping patterns in Fish community composition; information not provided using straight-line distances between lakes. Finally, the statistical methodology outlined in this paper provides a robust technique for assessing both the overall association between multivariate data matrices (i.e., landscape or regional scale), as well as facilitating the examination of smaller-scale relationships of individual observations (i.e., local scale).
Chuanbo Guo - One of the best experts on this subject based on the ideXlab platform.
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modelling Fish Communities in relation to water quality in the impounded lakes of china s south to north water diversion project
Ecological Modelling, 2019Co-Authors: Chuanbo Guo, Yushun Chen, Han Liu, Hui Yuan, Sovan Lek, Songguang XieAbstract:Large scale inter-basin water diversion projects would have a set of ecological and environmental impacts on aquatic ecosystems. However, knowledge regarding water transfer induced water quality changes in determining Fish Communities in the impounding ecosystems remain largely unknown. In the current study, we filled this research gap by using a set of machine learning algorithms to ensemble modelling Fish community indices with water quality indicators in the impounded lakes along the eastern route of China's South-to-North Water Diversion Project (SNWDP). Overall, our results realed that water quality changes can be good predictors for the variation of Fish community structures in these lakes. Although different model techniques highlighted different variable importance of water quality in determining Fish Communities, there is generally a consensus that the hydrological related water quality indicators like: water clarity (e.g., total suspended solids) and nutrient loading (e.g., phosphate) contributed the most to the changes of Fish Communities. Our results also indicated that water diversions could bring knock-on effects on Fish Communities. Thus, more attention should be paid to long-term ecological effects from future water diversions.