Dissimilarity In Species Composition Research Articles

Variations in Total Species Richness and the Unevenness of Species Abundance Distribution between Two Distant Conus Communities (Neogastropoda): A Case Study in Mannar Gulf (India)

The genus Conus forms a conspicuous and rather homogeneous group within marine Gastropods. This makes it all the more interesting to focus on the sub-communities formed by Conus species and to analyze the potential specificities in the internal organization of species in these communities, in particular species richness, species abundance distribution and the effect of geographical distance between communities on differences in their respective species composition. Accordingly, two Conus communities along the coast in Mannar Gulf (India), separated by 80 km, are considered. Reliable analysis requires, first, to treat exhaustive data from complete samplings or, else – as here – to implement an appropriate extrapolation procedure to complete numerically the partial samplings. After numerical completion, substantial differences were highlighted between the two communities, not only in terms of true (total) species richness but, even more, as regards the profile and the average unevenness of the distributions of species abundance. Also, significant dissimilarity in species composition was found between the two communities, that may be tentatively attributed to either deterministic distance decay in similarity of species composition or, alternatively, to the persistence in the stochastic process of species recruitment from the regional stock of Conus planktonic larvae. This preliminary study yet requests to be complemented by other similar case studies, before drawing any safer interpretative conclusions.

Comparison of automated extraction and amplification platforms on quantification of plasma HDV RNA: A multicenter study

Understanding how local environmental factors affect communities and compositional patterns are crucial to biodiversity conservation, especially in environments that were severally affected by anthropic actions. We analyzed the effects of fine-scale local environmental conditions on alpha and beta diversity of fern communities in three Atlantic forest areas and investigated the mechanisms underlying fern community responses. We sampled ferns and collected local environmental variables in 22 plots in three Atlantic forest areas and used multi-model inferences to identify the relationship between community diversity and composition and local environmental factors. We also applied multivariate analyses to verify whether community composition is constrained by local environmental factors. Finally, we analyzed beta-diversity (dissimilarity in species composition) patterns between and within forest areas and identified the contribution of turnover and nestedness to observed beta-diversity patterns. At the local scale, fern diversity was positively and strongly affected by fine-scale variations in nutrient availability and negatively influenced by soil acidity. Meanwhile, changes in community composition were also related to fine-scale variations in nutrient availability and soil rock coverage. Beta-diversity within forest areas (local scale) was as high as between forest areas (regional scale), a pattern that was virtually driven by species turnover at both scales of analysis. Our results highlight a prominent role of environmental filtering in regulating fine-scale local fern community diversity and composition, to such an extent that fine-scale local variation in species composition is as high as between spatially and climatically distant forest areas.

Environmental heterogeneity and dispersal limitation explain different aspects of β‐diversity in Neotropical fish assemblages

AbstractFrom a metacommunity perspective, patterns of β‐diversity emerge from the interplay between spatial and environmental processes. For obligate aquatic dispersers, river network constraints can be reflected in diversity patterns.Here, we aimed to determine the effects of environmental heterogeneity and spatial connectivity on β‐diversity components. We sampled fish assemblages in 21 sites across a longitudinal gradient. Beta‐diversity for taxonomic and functional composition among sites was decomposed into its turnover and nestedness components. We investigated whether environment was more important to functional β‐diversity and spatial factors had a higher contribution to dissimilarity in species composition. Further, we tested whether environmentally homogeneous sites with higher spatial connectivity showed lower compositional changes.We found that spatial factors were more important for taxonomic β‐diversity, whereas environment explained functional dissimilarity among habitats. Although environment and spatial factors contribute to total β‐diversity, they explained different components: while environment explained a higher portion of turnover, spatial factors were related to nestedness. The effects of mere spatial isolation and directional connectivity differed for species and functional β‐diversity and for the components of β‐diversity. Including directionality in spatial connectivity enabled the explanation of a higher proportion of variation of total species β‐diversity and its turnover.Our results suggest that niche and spatial processes may influence differently taxonomic and functional β‐diversity components. Thus, habitat filtering was the primary mechanism affecting functional diversity and species turnover, whereas spatial connectivity drove species nestedness.

Metaecosystem Dynamics of Marine Phytoplankton Alters Resource Use Efficiency along Stoichiometric Gradients.

Metaecosystem theory addresses the link between local (within habitats) and regional (between habitats) dynamics by simultaneously analyzing spatial community ecology and abiotic matter flow. Here we experimentally address how spatial resource gradients and connectivity affect resource use efficiency (RUE) and stoichiometry in marine phytoplankton as well as the community composition at local and regional scales. We created gradostat metaecosystems consisting of five linearly interconnected patches, which were arranged either in countercurrent gradients of nitrogen (N) and phosphorus (P) supply or with a uniform spatial distribution of nutrients and which had either low or high connectivity. Gradient metaecosystems were characterized by higher remaining N and P concentrations (and N∶P ratios) than uniform ones, a difference reduced by higher connectivity. The position of the patch in the gradient strongly constrained elemental stoichiometry, local biovolume production, and RUE. As expected, algal carbon (C)∶N, biovolume, and N-specific RUE decreased toward the N-rich end of the gradient metaecosystem, whereas the opposite was observed for most of the gradient for C∶P, N∶P, and P-specific RUE. However, at highest N∶P supply, unexpectedly low C∶P, N∶P, and P-specific RUE values were found, indicating that the low availability of P inhibited efficient use of N and biovolume production. Consequently, gradient metaecosystems had lower overall biovolume at the regional scale. Whereas treatment effects on local richness were weak, gradients were characterized by higher dissimilarity in species composition. Thus, the stoichiometry of resource supply and spatial connectivity between patches appeared as decisive elements constraining phytoplankton composition and functioning in metaecosystems.

Beta Diversity Patterns of Post-fire Forests in Central Yunnan Plateau, Southwest China: Disturbances Intensify the Priority Effect in the Community Assembly.

Post-fire succession is an ideal case for studying effects of disturbance on community assembly, and the key is to disentangle the contributions of assembly processes to the variation of community composition, namely beta diversity, and the contingent scales. The central Yunnan Plateau of Southwest China is characterized by monsoon related seasonal drought, and frequent forest fires. We sampled five fire sites burned in different years and a middle aged forest, measured species composition dissimilarity and its species turnover and nestedness components, within each fire site and across all sites. Results indicated species turnover as the primary component of beta diversity within all communities. There was no trend of change with year-since-fire (YSF) in beta diversity among early post-fire communities, but beta diversity in the middle aged community was significantly higher. Species turnover patterns across fire sites revealed a weak dispersal limit effect, which was stronger at lower than upper slope position for woody plants, and reverse for herbs. At the site scale, the species dissimilarity and turnover both enlarged with increasing slope position difference, especially in the middle-aged community, but the species nestedness had no consistent trend among sites, except a decreasing trend in the middle-aged forest. (Partial) Mantel tests indicated habitat filtering [primarily indicating total nitrogen (TN) and slope position] played a much stronger role than dispersal limit and YSF (indicating competition intensity) for the post-fire forest assembly at the landscape scale, for both woody and herbaceous layers. However, at the site scale, Mantel tests indicated a diminishing effect of soil nutrient filtering with increasing YSF, while effects of topography and spatial distance in the middle aged community was stronger. This divergence suggests the primary assembly mechanism gradually shift away from the soil constraint. While the seasonal drought and the mountain topography dominate the environmental legacy, our results imply that fires may reinforce a priority effect in the forests assembly in this region, by creating a habitat filtering (e.g., moisture and nitrogen limitation) effect on species composition in post-fire communities.

Composición y distribución de hepáticas (Marchantiophyta) en un intervalo altitudinal en la Cordillera Oriental de Colombia

Composition and distribution of liverworts (Marchantiophyta) in a continuous altitudinal range on the Cordillera Oriental of Colombia. The species composition of liverworts varies with altitude in the Northern part of the Andes due to the relationship of biotic (vegetation) and abiotic factors (temperature, humidity, and sunlight brightness). In order to test this affirmation we determined the diversity, species composition, abundance, and distribution of species of Marchantiophyta in an altitudinal range from 2 400 to 3 400 m on the Colombian Cordillera Oriental, and established how these vary with altitude and life-zones, regarding abiotic factors. Samples, taken every 200 m in the altitudinal range, and environmental data were registered during a year. We found 162 species, the composition of liverworts varied throughout the altitudinal gradient with a high number of unique species in each altitude. The maximum diversity was found at 3 000 m, along with a dominance of leafy habit and epiphytic species, while the higher richness of families and genera was found between 3 200 and 3 400 m. Anoplolejeunea conferta had the largest value of coverage in the zone, the highest value of importance value index (IVI), and the widest altitudinal distribution, from 2 400 to 3 000 m in four different substrates. The liverworts were distributed differently with altitude, we found a high beta diversity (0.864) due to the replacement of species, with more that 30 % of dissimilarity in species composition every 200 altitudinal meters, mainly depending on sunlight brightness variation. Accordingly, we found that abiotic factors like temperature, humidity, and sunlight brightness and its relationship vegetation are determinant in the diversity and altitudinal distribution of liverworts in the study area. Rev. Biol. Trop. 66(2): 559-570. Epub 2018 June 01.

Landscape‐scale vegetation homogenization in Central European sub‐montane forests over the past 50 years

AbstractQuestionsHow did plant species richness and spatial heterogeneity of the vegetation change across sub‐montane forests over the past 50 years? Did the vegetation changes reflect eutrophication, acidification and management changes, which the area underwent during the second half of the 20th century?LocationOrdinary managed forests sampled across 2500 km2 of a typical Central European sub‐montane landscape in the southern part of the Czech Republic.MethodsWe resampled 156 quasi‐permanent plots sampled in the 1950s–1970s and covering the whole range of forest vegetation in the region. We compared understorey plant species richness and community composition between the surveys and tested for temporal changes in the spatial heterogeneity (β‐diversity) of vegetation.ResultsSpecies richness and dissimilarity in species composition among plots decreased significantly between the surveys. The vegetation of the plots also changed significantly, but there were no clear directional changes across all plots. The vegetation homogenization was driven by local extinctions of specialist species, especially competitively weak species adapted to nutrient‐poor conditions. Few generalist species expanded between the surveys.ConclusionsWe found evidence of taxonomic homogenization of forest understoreys across a large sub‐montane region. This vegetation homogenization was probably driven by complex landscape changes that took place in the last century. Varied traditional management regimes were replaced with largely uniform management, and the once spatially diverse landscape mosaic has become simpler. The resulting transition to species‐poor and less variable vegetation was probably further accelerated by environmental eutrophication. Our results thus complement previous forest herb layer resurveys, which focused mostly on lowland forests and small nature reserves, and suggest that landscape‐scale taxonomic homogenization is occurring across Central European forests.

Environmental heterogeneity explains species turnover but not nestedness in fish assemblages of a Neotropical basin

Abstract Aim: Heterogenous environments can contribute to maintain biodiversity. Traditionally beta diversity studies have focused on determining the effect of environmental variables on the total dissimilarity of species composition. However, decomposing beta diversity in species replacement and nestedness could give new insights on mechanisms affecting spatial patterns of biodiversity. We aimed to answer two main questions about spatial patterns of fish diversity in a Neotropical basin: 1) whether some regions contribute differently to fish diversity, and 2) whether species turnover and nestedness are explained by environmental gradients. Methods Sampling sites in the main channel and tributaries of the Upper Paraná River were sampled between 2013 and 2015. We partitioned beta diversity and tested the relationship of turnover and nestedness with environmental variables. Results 74 species were captured. Some of these species were restricted to different sites, contributing to variation in species composition. Hill numbers showed a trend for higher diversity in the tributaries than in Paraná River sampling sites, and the partition of beta diversity revealed that species replacement drove dissimilarity in species composition. Only total beta diversity and turnover were related to environmental variables, mainly conductivity and turbidity. Conclusions Species diversity and composition of fish assemblages in the Upper Paraná River could be related to environmental gradients. Overall, our results suggest that Paraná River tributaries contribute to increase environmental heterogeneity, and hence to maintain a high diversity and variation in species composition. For that reason, we strongly recommend preserving highly heterogeneous habitats in the region.

Two decades of change in a field margin vegetation metacommunity as a result of field margin structure and management practice changes

Field margins have considerable ecological significance in agricultural landscapes by providing habitat and resources for farmland biodiversity. Few attempts have been made to examine the long term dynamics of multiple vegetation communities in field margins, at the landscape scale. In addition, drivers and processes governing such long term vegetation dynamics are poorly investigated. The aim of the study was to assess whether the diversity and composition of a field margin metacommunity have changed over the last two decades as a result of changes in both structural condition and management of field margins. In total, 309 field margins in north-western France, first surveyed in 1994, were resurveyed in 2015 by using the same protocol. Total species richness (gamma diversity) was stable over time while mean species richness per field margin (alpha diversity) increased. No difference in species composition dissimilarity (beta diversity) was recorded indicating that no biotic homogenization had occurred between 1994 and 2015. Species composition has shifted over time, with a decline of hemicryptophytes and an increase of shade-tolerant species. No change in Ellenberg nitrogen value was observed. Analysis of drivers revealed a significant influence of changes in the structural condition of field margins, i.e. the development of the tree layer, on vegetation diversity. Dominant height of vegetation and tree cover were highest in 2015 compared with 1994. This has likely been driven by a decline in intensity of field margin management. Despite changes in alpha diversity, the field margin metacommunity had a stable Clementsian structure over time, suggesting grouped distribution of species along environmental gradients. This study provides a rare example of the long term vegetation change in field margins in relation with margin structure and management changes, using permanent plots and diachronic data. Results highlight the need to maintain a variety of differently structured and managed field margins to preserve high plant diversity. They underline the need to place conservation strategies in the context of regional-scale processes to ensure the long-term conservation of field margin metacommunities.

Winter supplementary feeding influences forest soil seed banks and vegetation

AbstractQuestionTo what extent does winter supplementary feeding influence vegetation and soil seed banks in forest ecosystems?LocationBiałowieża Primaeval Forest, NE Poland.MethodsSeveral dozen feeding stations, each composed of one to several haystacks, are used in Białowieża Forest for supplementary winter feeding of European bison (Bison bonasus). We checked the species composition and availability of seeds in hay in 15 haystacks of the eight oldest feeding stations, which could be a potential source of seeds. Vegetation and soil seed bank were sampled on the overlapping 10 m × 10 m plots distributed along 500‐m long transects running south and north of the studied feeding stations. Seed content in the soil samples was studied by the seedling emergence method in an unheated greenhouse.ResultsWe revealed high dissimilarity of species composition of the hayseed, soil seed bank and standing vegetation. The dissimilarity between soil seed banks and standing vegetation increased with the distance from the haystack. The species richness of the standing vegetation was not affected by distance to the haystack, while seed bank species richness showed a significant negative correlation with distance. The mean weighted ecological indicator values of pH, light and soil fertility were negatively correlated with the distance from the haystack for the seed bank and the standing vegetation. The percentage of damaged bushes and juvenile trees was positively correlated with their density and decreased with the distance from the haystack.ConclusionsWe revealed distinct but local (25–50 m off the haystack) effect of supplementary feeding on the vegetation and soil seed banks of forest ecosystems. Taking into account the ecosystem approach to nature conservation, the winter feeding in forest ecosystems should be concentrated in few places to avoid the expansion of non‐native plant species in forest ecosystems. To prevent potential plant invasions, the origin of the hay used as supplementary winter fodder should be carefully selected, with a preference for local origin and making of hay of native plant species in the forest's meadows or in its surroundings.

Quantifying long-term plant community dynamics with movement models: implications for ecological resilience.

Quantification of rates and patterns of community dynamics is central for understanding the organization and function of ecosystems. These insights may support a greater empirical understanding of ecological resilience, and the application of resilience concepts toward ecosystem management. Distinct types of dynamics in natural communities can be used to interpret and apply resilience concepts, but quantitative methods that can systematically distinguish among them are needed. We develop a quantitative method to analyze long-term records of plant community dynamics using principles of movement ecology. We analyzed dissimilarity of species composition through time with linear and nonlinear statistical models to assign community change to four classes of movement trajectories. Compositional change in each sampled plot through time was classified into four classes, stability, abrupt nonlinear change, transient reversible change, and gradual linear drift, each representing a different aspect of ecological resilience. These competing models were evaluated based on estimated coefficients, goodness of fit, and parsimony. We tested our method's accuracy and robustness through simulations, or the ability to distinguish among trajectories and classify them correctly. We simulated 16,000 trajectories of four types, of which 94-100% were correctly classified. Next, we analyzed 13 long-term vegetation records from North American grasslands (annual grasslands with warm-season and cool-season communities, shortgrass, mixedgrass, and tallgrass prairies, and sagebrush steppe), and a record of primary succession at Mt. St. Helens volcano. Collectively, we analyzed 14,647 observations from 775 plots, between 1915 and 2012. Dynamics could be reliably assigned for 705 plots (91%), and overall statistical fit was high (goodness of fit, 0.77±0.15 SD). Among the perennial grasslands, stability was most common (44% of all plots), followed by gradual linear (22%), abrupt nonlinear (17%), and reversible (6%) change. Among annual grasslands, abrupt nonlinear shifts (33%) were more common in the warm-season community than in the cool-season (20%). As expected, abrupt nonlinear change was common during primary succession (51%) while reversible change was rare (3%). Generally, reversible dynamics often required 2-3 decades. Analysis of long-term community change, or trajectories, with principles of movement ecology provides a quantitative basis to compare and interpret ecological resilience within and among ecosystems.

Coccolithophore ecology in the tropical and subtropical Atlantic Ocean: New perspectives from the Atlantic meridional transect (AMT) programme

Coccolithophore species composition was determined in 199 samples collected from the upper 300m of the Atlantic Ocean, spanning temperate, tropical and subtropical waters in both hemispheres during four Atlantic Meridional Transect (AMT) cruises over the period 2003–2005. Of the 171 taxa observed, 140 consistently represented <5% of total cell numbers, and were classed as rare. Multivariate statistical techniques were used on the common taxa to assess variability in community composition vertically in the water column, horizontally across hydrographic provinces (subtropical gyres, equatorial waters, temperate waters), and temporally between cruises. Sharper gradients of statistical dissimilarity in species composition occurred vertically over a few tens of metres than horizontally over hundreds of kilometres. Three floral groups were identified from analysis of the depth of normalised abundance maxima in the subtropical gyres and equatorial waters: the upper euphotic zone (UEZ, >10% surface irradiance); the lower euphotic zone (LEZ, 10–1% surface irradiance); and the sub-euphotic zone (SEZ, <1% surface irradiance). The LEZ includes the deep chlorophyll maximum (DCM) and nutricline, and was characterised by species such as Emiliania huxleyi and Gephyrocapsa ericsonii which were also abundant at higher latitudes. It is suggested that this pattern reflects similarities in the light (and inorganic nutrient) conditions between the LEZ and temperate waters. The SEZ is below the depth where light is thought to be sufficient to support photosynthesis, suggesting that deep-dwelling species such as Florisphaera profunda and Gladiolithus spp. may be mixotrophic or phagotrophic, although conclusive proof will need to be gained experimentally. Mixotrophy could also be an important nutritional strategy for species abundant (Umbellosphaera spp., holococcolithophores) in the UEZ where inorganic nutrient concentrations are depleted and limiting to growth, although other nutritional strategies, such as the use of organic nutrients, are also possible. Statistical differences were also found in the species composition between the different cruises, with high levels of similarity for similar timed cruises (May or September–October). Few individual taxa showed significant variability in abundance over the time-span of sampling, except species such as E. huxleyi and G. ericsonii at higher latitudes. In subtropical and equatorial waters, high levels of species richness and low levels of species dominance remained throughout the sampling period indicating that seasonal fluctuations reflected differences in the whole coccolithophore community rather than in just one or a few species. Multivariate analyses of the taxa classified as rare also indicated some level of temporal, as well as vertical, zonation. Such insights into coccolithophore ecology and community composition provide important new perspectives that require innovative research to fully understand their impact on ocean biogeochemistry.

Traditional forest management practices stop forest succession and bring back rare plant species

Summary Past management practices may continue to influence ecosystem functions and processes for decades, centuries or even longer after they have been abandoned. Until now, few researchers have attempted experiments which test the effects of restoring some of these past management practices on long‐term community developmental trajectories. Strong evidence indicates that the diversity of various taxonomic groups declined in European lowland forests in the second half of the 20th century, following the abandonment of some traditional forest management practices. We carried out a five‐year field trial in a lowland thermophilous oak forest to describe the effects of restoration of litter raking and grass cutting on the long‐term developmental trajectory of species composition and the diversity of understorey vegetation. We used target species groups, that is species specific to thermophilous forests and dry grassland vegetation and plant functional traits to evaluate the restoration success using both compositional and functional outcomes. Dissimilarity in species composition between the managed plots and controls increased significantly during the 5 years of the trial. Litter raking increased the richness and cover of the thermophilous forest and dry grassland species, whereas grass cutting increased the richness and cover of only the dry grassland species. We did not record any overall trends in divergence of functional trait composition between managed and control plots. In the litter raking plots, we recorded increases in community‐weighted means of specific leaf area, in lateral spread and in Ellenberg indicator values for nutrients and soil reaction. In contrast, we found little evidence for predictability of species functional trait composition subjected to grass cutting. Synthesis and applications. Following the restoration of traditional forest management practices, we were able to change the community's developmental trajectory towards higher richness and cover of target species. The evaluation of community developmental trajectories using species and functional trait composition supports the idea that restoration of traditional forest management practices should carefully distinguish among possible interventions.

How Biotic Differentiation of Human Impacted Nutrient Poor Deciduous Forests Can Affect the Preservation Status of Mountain Forest Vegetation

A significant loss of biodiversity resulting from human activity has caused biotic homogenisation to become the dominant process shaping forest communities. In this paper, we present a rare case of biotic differentiation in European temperate deciduous forest herb layer vegetation. The process is occurring in nutrient poor oak-hornbeam forests in mountain areas (Polish Eastern Carpathians, Central Europe) where non-timber use was converted into conventional forest management practice. This change contributed to increases in the nitrogen content and pH reaction of the soil that, contrary to predominant beliefs on the negative impact of habitat eutrophication on diversity, did not result in a decrease in the latter. We discuss possible reasons for this phenomenon that indicate the important role of tree stand composition (an increasing admixture of beech worsening the trophic properties of the soil). The second issue considered involves the effect of the changes in herb species composition of oak-hornbeam forest on its distinctiveness from the beech forest predominating in the Polish Eastern Carpathians. Unfortunately, despite the increase in the species compositional dissimilarity of oak-hornbeam forest, a reduction in their distinctiveness in relation to the herb species composition of beech forest was found. Such a phenomenon is an effect of the major fragmentation of oak-hornbeam forests, a spread of beech forest-type species, and forest management that gives preference to beech trees. Consequently, it can be expected that changes occurring in oak-hornbeam forest vegetation will contribute to a decrease in the forest vegetation variability at the regional scale.

Zonation patterns, composition and diversity of macroalgal communities in the eastern coasts of Qeshm Island, Persian Gulf, Iran

This study investigates the spatial and temporal variation of intertidal macroalgae along the eastern coasts of Qeshm Island, Persian Gulf, Iran. Monthly sampling of abundance, biomass, richness and diversity of macroalgae at three intertidal levels was carried out at two different sites during 1 year. The samples were collected every month using quadrats (0.5 × 0.5 m) from October 2012 to September 2013. The species dry weight was applied to examine changes in biomass and assemblage composition of intertidal macroalgae using univariate and multivariate analyses. A total of 42 seaweed species (10 Chlorophyta, 9 Phaeophyceae, and 23 Rhodophyta) were identified. The results confirmed a temporal pattern in the growth of the algal species which also showed a biomass zonation pattern from upper to lower intertidal. The annual mean biomass of macroalgae was highest in winter (29.3 ± 9.8 g dry wt m−2) and the lowest in autumn (17.3 ± 13.5 g dry wt m−2). The annual dominant species by biomass was Padina sp. followed by Padina australis. The most common species in the area, during the sampling period include Ulva intestinalis, Ulva lactuca, Palisada perforata and Padina sp. According to the similarity percentages analysis (SIMPER), the species Ulva intestinalis, Dictyosphaeria cavernosa (Chlorophyta), Padina australis (Phaeophyceae), Champia spp., Centroceras clavulatum and Palisada perforata (Rhodophyta) were responsible for the most dissimilarity of species composition between four seasons during the sampling period. BIOENV analysis indicated that the main environmental factors structuring macroalgal community at the study area were TDS and pH. The simple macroalgae community on the eastern coast of Qeshm Island and absence of slow-growing perennial macroalgae, such as members of the Sargassaceae, known from the lower shore at other intertidal localities along the island’s coast might relate to the predominantly unsuitable sandy-stony substrates unsuitable for their colonization and the unfavourable impact upon them of urbanization.

Processes underpinning fish species composition patterns in estuarine ecosystems worldwide

AbstractAimWe present the first global biogeographical regionalization of estuaries, assessing how dispersal limitation and/or environmental filtering mechanisms drive the patterns of fish assemblage composition among and within biogeographical regions.LocationEstuaries worldwide.MethodsA bootstrapped hierarchical cluster analysis was applied to define biogeographical regions based on pairwise beta diversity (βsim) of fish assemblages among 393 estuaries worldwide. Variables representing dispersal limitation and environmental features were used to disentangle the possible effects of assembly processes acting among and within biogeographical regions, through hierarchical partitioning of variation. Finally, we assessed the contribution of species to beta diversity through a method newly developed in this article.ResultsEstuaries were grouped into seven major biogeographical regions explained by geographical dispersal variables. Dissimilarity in species composition within each biogeographical region was mainly determined by ecosystem‐connectivity dispersal variables, with a minor influence of environmental variables (chiefly sea surface temperature). Marine species contributed highly to beta diversity between estuaries but less than expected by chance, whilst freshwater species had low contributions yet also less than expected. Estuarine (i.e. brackish) and diadromous species had low contributions to beta diversity but higher than expected by chance.Main conclusionsFish assemblage composition in estuaries seems to be driven by dispersal limitation processes both among and within biogeographical regions, with only a minor role of environmental filtering evident within biogeographical regions. These findings contrast with the acknowledged importance of environmental variables as drivers of species richness patterns. Irrespective of biogeographical region, the ecosystem affinity of a species determined its contribution to beta diversity between estuaries. The new method presented here offers new opportunities for assessing the effects of taxonomic and functional aspects on beta diversity (βsim) across taxa and ecosystems, and thus contributes to improving knowledge of assembly processes.

The evolution of the competition-dispersal trade-off affects α- and β-diversity in a heterogeneous metacommunity.

Difference in dispersal ability is a key driver of species coexistence in metacommunities. However, the available frameworks for interpreting species diversity patterns in natura often overlook trade-offs and evolutionary constraints associated with dispersal. Here, we build a metacommunity model accounting for dispersal evolution and a competition-dispersal trade-off. Depending on the distribution of carrying capacities among communities, species dispersal values are distributed either around a single strategy (evolutionarily stable strategy, ESS), or around distinct strategies (evolutionary branching, EB). We show that limited dispersal generates spatial aggregation of dispersal traits in ESS and EB scenarios, and that the competition-dispersal trade-off strengthens the pattern in the EB scenario. Importantly, individuals in larger (respectively (resp.) smaller) communities tend to harbour lower (resp. higher) dispersal, especially under the EB scenario. We explore how dispersal evolution affects species diversity patterns by comparing those from our model to the predictions of a neutral metacommunity model. The most marked difference is detected under EB, with distinctive values of both α- and β-diversity (e.g. the dissimilarity in species composition between small and large communities was significantly larger than neutral predictions). We conclude that, from an empirical perspective, jointly assessing community carrying capacity with species dispersal strategies should improve our understanding of diversity patterns in metacommunities.

Relationship of Productivity to Species Richness in the Xinjiang Temperate Grassland.

The relationship between species richness (SR) and aboveground net primary productivity (ANPP) is still a central and debated issue in community ecology. Previous studies have often emphasized the relationship of alpha diversity (number of species identity) to the mean ANPP with respect to the SR-ANPP relationship while neglecting the contribution of beta diversity (dissimilarity in species composition) to the mean ANPP and to the stability of ANPP (coefficient of ANPP: CV of ANPP). In this study, we used alpha and beta diversity, mean ANPP and the CV of ANPP collected from 159 sites and belonging to three vegetation types in the Xinjiang temperate grassland to first examine their trends along climatic factors and among different vegetation types and then test the relationship among alpha (beta) diversity and mean ANPP and the CV of ANPP. Our results showed that in the Xinjiang temperate grasslands, alpha diversity was positively and linearly correlated with MAP but unimodally correlated with MAT. Meanwhile, beta diversity was unimodally correlated with MAP but linearly correlated with MAT. Relative to desert steppe, meadow steppe and typical steppe had the highest alpha and beta diversity, respectively. Except for ANPP exhibiting a quadratic relationship with MAP, no significant relationship was found among ANPP, the CV of ANPP and climatic factors. ANPP and the CV of ANPP also exhibited no apparent patterns in variation among different vegetation types. Our results further showed that mean ANPP was closely associated with alpha diversity. Both linear and unimodal relationships were detected between alpha diversity and mean ANPP, but their particular form was texture-dependent. Meanwhile, the CV of ANPP was positively correlated with beta diversity. Our results indicated that in addition to incorporating alpha diversity and mean ANPP, incorporating beta diversity and the CV of ANPP could expand our understanding of the SR-ANPP relationship.

Productivity–diversity relationships in reservoir phytoplankton communities in the semi-arid region of northeastern Brazil

The aims of study were to 1) evaluate the productivity–diversity relationships (PDR) in reservoir phytoplankton communities in the semi-arid of northeastern Brazil on the local and regional scales; 2) determine the association between regional dissimilarity in species composition and regional mean productivity; 3) test the potential of productivity as well as physical and chemical factors of the water as descriptors of phytoplankton diversity using generalized linear models. Nutrient availability (total nitrogen and total phosphorus) and phytoplankton biomass were used as measures of productivity, whereas species richness as measure of diversity. Unimodal PDR was found when total phosphorus and biomass were considered as measure of productivity. Regional dissimilarity diminished with regional mean productivity. This finding may be attributed to the effect of eutrophication on diminishing the differences in the composition of species between compartments within each reservoir, leading to a loss of diversity in these ecosystems. Moreover, the analysis of the models demonstrated evidence that PDR may be influenced by environmental factors, such as electrical conductivity, total dissolved solids and pH in reservoirs located in semiarid regions of northeastern Brazil.

Лесные луга Западно-Сибирской равнины и новый взгляд на систему порядка Carici macrourae–Crepidetalia sibiricae

Forest meadows is a characteristic vegetation type of the forest landscapes fr om the Altai-Sayan mountains on the east to the Southern Urals on the west. Communities inhabit open sites that were formed during natural or anthropogenic dynamic of zonal forests. It is the main reason of the floristic origina­lity of the meadows, as reflected by the presence of numerous forest species. Our study is based on the analysis of 573 relevés from 27 associations represented in the previous publications. All forest meadows of the Southern Siberia and Southern Urals are included in the order Carici macrourae–Crepidetalia sibiricae Ermakov et al. 1999 (Ermakov et al., 1999). Among the differential species (d. s.) are common forest herbs: Aegopodium podagraria, Brachypodium pinnatum, Bupleurum aureum, Calamagrostis arundinacea, Crepis sibirica, Dracocephalum ruyschiana, Geranium pseudosibiricum, Hieracium umbellatum, Lilium pilosiusculum, Lupinaster pentaphyllus, Pulmonaria mollis, Rubus saxatilis. CA-ordination shows that the moisture and geographical position are the most important factors influencing the differentiation of forest meadows. Strict dissimilarity in species composition is found between 3 regions — the Altai-Sayan mountains, West Siberian Plain and Southern Urals. The order Carici macrourae–Crepidetalia sibiricae includes three regional alliances. The alliance Crepidion sibiricae Mirkin ex Ermakov, Maltseva et Makunina 1999 (d. s.: Aegopodium podagraria, Brachypodium pinnatum, Bupleurum aureum, Calamagrostis arundinacea, Crepis sibirica, Dracocephalum ruyschiana, Geranium pseudosibiricum, Hieracium umbellatum, Lilium pilosiusculum, Lupinaster pentaphyllus, Pulmonaria mollis, Rubus saxatilis) unites meadows of piedmonts and low mountains of the Altai, Kuznetsk Alatau and Salair. The alliance Heracleo sibirici–Geranion bifolii all. nov. (d.s.: Cirsium setosum, Geranium bifolium, Hera­cleum sibiricum, Poa palustris, Populus tremula, Veronica longifolia, Vicia megalotropis) occurs almost all over the southern part of the West Siberian Plain (Lashchinsky, Tishchenko, 2011; Tishchenko, 2015). The coenoses inhabit the edges of the deciduous ­forests. The alliance Polygonion krascheninnikovii Kashapov 1985 (d. s.: Bistorta major, Geum rivale, Hylotelephium triphyllum, Rumex acetosa, Stachys officinalis, Trifolium medium, Veronica chamaedrys, Viola tricolor) represents communities of the Southern Urals forest belt (Kashapov, 1985; Filinov et al., 2002; Yamalov et al., 2012). Three regional alliances of forest meadows well correspond to the syntaxonomy structure of the class Brachypodio pinnati–Betuletea pendulae Ermakov et al. 1991 with three orders — Carici macrourae–Pinetalia sylvestris Ermakov et al. 1991 (mostly Altai-Sayan mountains), Calamagrostio epigeii–Betuletalia pendulae Korolyuk ex Ermakov et al. 2000 (West Siberian Plain) and Chamaecytiso ruthenici–Pinetalia sylvestris Solomeshch et Ermakov in Ermakov et al. 2000 (Southern Ural). Ranges of this forest orders overlap the areas of corresponding meadow alliances in general. The coniferous and deciduous forests are replaced by grasslands in natural or anthropogenic chronosequences leading to a floristic similarity ­between forest and meadow communities. The moisture gradient is significant for the species composition of meadows. It determines the division of alliances into suballiances of moderately moist and dry forest meadows. Many of xeromesophytes of the class Festuco-Brometea Br.-Bl. et Tx. ex Klika et Hadać 1944 and the order Galietalia veri Mirkin et Naumova 1986 are used as differential species of dry forest meadow suballiances. In diagnosis of moderately moist communities we use forest ­hygromesophytes. The suballiance Crepidenion sibiricae suball. nov. unites moderately moist forest meadows of humid and subhumid regions of the Altai-Sayan mountains. The associations of Aconito barbati–Vicenion unijugae suball. nov. prefer drier habitats. The alliance Anthrisco sylvestris–Aconitenion volubilis suball. nov. is restricted to the Ob-Irtysh watershed (south-eastern regions of the West Siberian Plain). The communities are located at the edges of wet deciduous forests. The west siberian suballiance Heracleo sibirici–Artemisenion macranthae suball. nov. is widespread in southern part of forest zone and northern part of forest-steppe zone. The suballiance Polygonenion krasсheninnikovii Mukhamediarova ex Yamalov et Sultangareeva 2010 represents ­moderately moist meadows of the Southern Ural mountain forest belt. Communities are common both on gentle slopes and in river valleys wh ere they occupy edges and clearings in pine and pine-birch ­forests. Dry variants of forest meadows are included in the suballiance Amoriо montanae–Polygonenion krasсheninnikovii Yamalov suball. nov. These communities are common both on convex slopes and hilltops as well as in dry habitats of river valleys in forest belt along the Southern Urals and forest-steppe belt of the South-Eastern Urals. The analysis of moisture conditions using species indicator values (Korolyuk, 2006) shows similar borderlines between the moderately moist and dry forest meadows: near 61 grade in the Altai-Sajan and Ural mountains, 62 grade — for the West Siberian Plain with wide distribution of the waterlogged landscapes. The analysis of forest meadows demonstrates the necessity in the revision of some associations and subassociations. Formally defined differential species in many cases differ from ones proposed by authors of syntaxa. Some associations are represented by a few relevés and need an additional data. Ecological ranges of some syntaxa along the moisture gradient are overlapped that explains the importance of ecological and geographical analysis of associations and subassociations.