Independent evolution of leaf and root traits within and among temperate grassland plant communities

In this study, we used data from temperate grassland plant communities in Alberta, Canada to test two longstanding hypotheses in ecology: 1) that there has been correlated evolution of the leaves and roots of plants due to selection for an integrated whole-plant resource uptake strategy, and 2) that trait diversity in ecological communities is generated by adaptations to the conditions in different habitats. We tested the first hypothesis using phylogenetic comparative methods to test for evidence of correlated evolution of suites of leaf and root functional traits in these grasslands. There were consistent evolutionary correlations among traits related to plant resource uptake strategies within leaf tissues, and within root tissues. In contrast, there were inconsistent correlations between the traits of leaves and the traits of roots, suggesting different evolutionary pressures on the above and belowground components of plant morphology. To test the second hypothesis, we evaluated the relative importance of two components of trait diversity: within-community variation (species trait values relative to co-occurring species; α traits) and among-community variation (the average trait value in communities where species occur; β traits). Trait diversity was mostly explained by variation among co-occurring species, not among-communities. Additionally, there was a phylogenetic signal in the within-community trait values of species relative to co-occurring taxa, but not in their habitat associations or among-community trait variation. These results suggest that sorting of pre-existing trait variation into local communities can explain the leaf and root trait diversity in these grasslands.     

Patterns of functional and taxonomic organization of stream fishes: inferences based on α, β, and γ diversities

The primary objective of this study was to determine whether total biodiversity (γ) is partitioned into within‐community (α) and among‐community (β) components differently for taxonomic and functional organization. I hypothesized that α diversity will contribute more to the functional organization of γ diversity and that β diversity will contribute more to the taxonomic organization of γ diversity. A secondary objective was to determine whether the relationship between taxonomic and functional diversity is scale dependent. Species abundance data was obtained from fisheries surveys conducted by the Texas Parks and Wildlife Dept that focused on least disturbed streams from 11 different ecoregions of Texas, including 62 localities from 18 drainages. Functional and taxonomic organization of assemblages was quantified with two different measures of biodiversity, including richness and the numbers equivalent of Shannon diversity. Scale‐dependent effects on these indices were assessed by multiplicatively partitioning γ into α and β components. The contribution of α and β components to γ diversity differed between functional and taxonomic organization and among different measures of biodiversity. Among‐community components were more influential in structuring the taxonomic organization of stream‐fish assemblages, whereas within‐community components were more important in structuring the functional organization of assemblages. The relationship between taxonomic and functional diversity differed between α and β components and between spatial scales. Indeed, ecological patterns not only change with spatial scale, but how they change is dependent on which aspect of biodiversity is considered.     

A functional trait-based approach to understand community assembly and diversity–productivity relationships over 7 years in experimental grasslands

Several multi-year biodiversity experiments have shown positive species richness–productivity relationships which strengthen over time, but the mechanisms which control productivity are not well understood. We used experimental grasslands (Jena Experiment) with mixtures containing different numbers of species (4, 8, 16 and 60) and plant functional groups (1–4; grasses, legumes, small herbs, tall herbs) to explore patterns of variation in functional trait composition as well as climatic variables as predictors for community biomass production across several years (from 2003 to 2009). Over this time span, high community mean trait values shifted from the dominance of trait values associated with fast growth to trait values suggesting a conservation of growth-related resources and successful reproduction. Increasing between-community convergence in means of several productivity-related traits indicated that environmental filtering and exclusion of competitively weaker species played a role during community assembly. A general trend for increasing functional trait diversity within and convergence among communities suggested niche differentiation through limiting similarity in the longer term and that similar mechanisms operated in communities sown with different diversity. Community biomass production was primarily explained by a few key mean traits (tall growth, large seed mass and leaf nitrogen concentration) and to a smaller extent by functional diversity in nitrogen acquisition strategies, functional richness in multiple traits and functional evenness in light-acquisition traits. Increasing species richness, presence of an exceptionally productive legume species (Onobrychis viciifolia) and climatic variables explained an additional proportion of variation in community biomass. In general, community biomass production decreased through time, but communities with higher functional richness in multiple traits had high productivities over several years. Our results suggest that assembly processes within communities with an artificially maintained species composition maximize functional diversity through niche differentiation and exclusion of weaker competitors, thereby maintaining their potential for high productivity.     

Increasing variation in taxonomic distinctness reveals clusters of specialists in the deep sea

Changes in biodiversity with latitude or along a given environmental gradient have been described in many studies, including for marine ecosystems. Currently there is no scientific consensus, however, regarding macroecological patterns of diversity vs depth. Here, we describe variation in the biodiversity of fishes along a depth gradient from 0 to 2000 m in the region of the Norfolk Ridge and Lord Howe Rise (Western Pacific), using data obtained during the NORFANZ voyage. We modelled α diversity (richness), β diversity (using Jaccard's coefficient), evenness, taxonomic distinctness and taxonomic resemblances among fish communities. Although α diversity did not change appreciably with depth, β diversity decreased significantly in deeper strata. Both taxonomic resemblances and Jaccard similarities diminished with depth, indicating convergence in community structure. In addition, average taxonomic distinctness showed no clear pattern with depth, but taxonomic trees constructed among species within deeper samples had more variable path‐lengths than those in shallower samples. The presence of taxonomically distinct clusters of highly related species at depth indicates specialised niches that have developed in a relatively extreme (dark, pressurized) yet stable environment. We propose that reduced β diversity and increased variation in taxonomic distinctness might serve as indicators of ecological communities living in harsh environments – a hypothesis that should be tested in other systems, such as deserts, high altitudes or latitudes.     

A functional perspective for breeding and wintering waterbird communities: temporal trends in species and trait diversity

Waterbird communities are prone to strong temporal changes both seasonally and annually, but little is known about how this affects their functional diversity and community assembly. Detecting temporal trends in taxonomic and functional diversity within (alpha diversity) and between (beta diversity) communities in breeding and wintering seasons could give insight into the ecological processes driving those trends. In this study, we investigated trends in wintering and breeding waterbirds within and between eleven wetlands in Mediterranean Spain, using a 28‐year time‐series up to 2017. We assessed the temporal trends in taxonomic and functional diversity measures, and compared observed functional diversity values with null expectations, in order to explore the mechanisms driving community assembly. We found increases over time in species richness and in the occupied functional space for both wintering and breeding communities, indicating that species with distinct functional roles were added in both seasons. However, the distribution of the abundances in the functional space was different for breeding and wintering communities. Dissimilarity of species and functional traits decreased among wetlands, suggesting that some of the same functional traits were added to the different wetlands, increasing regional homogenization through time. This is reflected in increases over time in mean body mass, diet plasticity and in the importance of fish in waterbird diets, plus declines in the dietary importance of invertebrates and in plasticity of feeding strata. Furthermore, species composition between wintering and breeding communities, but not trait composition, has become more similar through time. Our results highlight that annual changes, and especially seasonal changes, in the composition of waterbird communities have different effects on their functional diversity, and are influenced by opposing community assembly mechanisms.     

Taxonomic and functional homogenisation of macroinvertebrate communities in recently intermittent Alpine watercourses

1. Mountain streams in southwestern European Alps are currently shifting from perennial to intermittent flow due to the combined effects of climate change and local anthropogenic pressures. Given that flow intermittency is a recently documented phenomenon in the Alps, only scattered studies have investigated functional and taxonomical diversity of benthic invertebrate communities in recently intermittent Alpine streams.
2. We used a hierarchical sampling design to investigate patterns in taxonomic and functional diversity of benthic invertebrate communities in 13 recently intermittent Alpine streams in north-west Italy. in April 2017, we sampled benthic communities in two reaches of each stream with different hydrological conditions: a control reach, with permanent flow; and an intermittent reach, which recently experienced non-flow periods in summer.
3. We tested for the response of taxonomic richness at multiple spatial scales by partitioning total diversity into the average richness of local communities and the richness due to variation among local communities both within and among reaches. By partitioning total diversity (γ) into its local (α) and turnover (β) components we showed a decrease in local and regional species richness both within and among reaches, whereas variation among communities was significantly lower in intermittent reaches at the reach scale only.
4. The analysis of multidimensional trait space of macroinvertebrate communities in reaches with different hydrological conditions revealed a significant reduction of functional diversity, dispersion, and evenness in intermittent reaches. There was trait overdispersion in intermittent reaches, as these hosted both typical Alpine taxa and organisms adapted to flow intermittency. In particular, we observed the replacement of taxa with aquatic respiration and those preferring medium- to fast-flowing oligotrophic waters by taxa adapted to lentic habitats, air breathing and with larval dormancy phases.
5. These results indicate that recent flow intermittency has caused drastic changes in benthic invertebrate communities in Alpine streams. Our work highlights the importance of integrating taxonomic and functional diversity to thoroughly assess the impacts of flow intermittency.

     

CWM and Rao’s quadratic diversity: a unified framework for functional ecology

Assessing the effects of environmental constraints on community structure often relies on methods that consider changes in species functional traits in response to environmental processes. Various indices have been proposed to measure relevant aspects of community trait composition from different viewpoints and perspectives. Among these, the ‘community-weighted mean trait value’ (CWM) and the Rao coefficient have been widely used in ecological research for summarizing different facets of functional composition and diversity. Analyzing changes in functional diversity of bee communities along a post-fire successional gradient in southern Switzerland we show that these two measures may be used to describe two complementary aspects of community structure, such as the mean and the dispersion of functional traits within a given species assemblage. While CWM can be adequately used to summarize shifts in mean trait values within communities due to environmental selection for certain functional traits, the Rao coefficient can be effectively applied to analyze patterns of trait convergence or divergence compared to a random expectation.     

Community Functional Responses to Soil and Climate at Multiple Spatial Scales: When Does Intraspecific Variation Matter?

Despite increasing evidence of the importance of intraspecific trait variation in plant communities, its role in community trait responses to environmental variation, particularly along broad-scale climatic gradients, is poorly understood. We analyzed functional trait variation among early-successional herbaceous plant communities (old fields) across a 1200-km latitudinal extent in eastern North America, focusing on four traits: vegetative height, leaf area, specific leaf area (SLA), and leaf dry matter content (LDMC). We determined the contributions of species turnover and intraspecific variation to between-site functional dissimilarity at multiple spatial scales and community trait responses to edaphic and climatic factors. Among-site variation in community mean trait values and community trait responses to the environment were generated by a combination of species turnover and intraspecific variation, with species turnover making a greater contribution for all traits. The relative importance of intraspecific variation decreased with increasing geographic and environmental distance between sites for SLA and leaf area. Intraspecific variation was most important for responses of vegetative height and responses to edaphic compared to climatic factors. Individual species displayed strong trait responses to environmental factors in many cases, but these responses were highly variable among species and did not usually scale up to the community level. These findings provide new insights into the role of intraspecific trait variation in plant communities and the factors controlling its relative importance. The contribution of intraspecific variation to community trait responses was greatest at fine spatial scales and along edaphic gradients, while species turnover dominated at broad spatial scales and along climatic gradients.     

山西关帝山森林群落物种、谱系和功能多样性海拔格局

探索和揭示生物多样性的空间格局和维持机制是生态学和生物地理学研究的热点内容, 但综合物种、系统进化和功能属性等方面的多样性海拔格局研究很少。该文以关帝山森林群落为研究对象, 综合物种、谱系和功能α和β多样性指数, 旨在初步探讨关帝山森林群落多样性海拔格局及其维持机制。研究结果表明: 随着海拔的升高(1 409-2 150 m), 关帝山森林群落物种丰富度指数(S)、谱系多样性指数(PD)和功能丰富度指数(FRic)整体上表现出上升的趋势, 特别是海拔1 800 m以上区域。随着海拔的升高, 总β多样性(β_total)和更替(β_repl)上升趋势明显, 而丰富度差异(β_rich)则逐渐下降。不同生活型植物的物种、谱系和功能多样性海拔格局差异较大。随着海拔的升高, 草本植物S和物种多样性指数(H′)上升趋势高于木本植物。影响草本植物S分布的主要因素是地形因子, 而影响木本植物S分布的主要因素是历史过程。随着海拔的升高, 木本植物β_total上升趋势要比草本植物明显。随着海拔的升高, 木本植物β_repl和β_rich分别表现出单峰格局和“U”形格局, 而草本植物β_repl和β_rich则分别表现出单调递增和单调递减的格局。随着环境差异和地理距离的增加, 群落间物种、谱系和功能β多样性显著增加。环境差异(环境过滤)对木本植物的β多样性具有相对较强的作用; 而环境差异(环境过滤)和地理距离(扩散限制)共同作用于草本植物的β多样性。     

Processes of community assembly in an environmentally heterogeneous,high biodiversity region

Despite decades of study, the relative importance of niche‐based versus neutral processes in community assembly remains largely ambiguous. Recent work suggests niche‐based processes are more easily detectable at coarser spatial scales, while neutrality dominates at finer scales. Analyses of functional traits with multi‐year multi‐site biodiversity inventories may provide deeper insights into assembly processes and the effects of spatial scale. We examined associations between community composition, species functional traits, and environmental conditions for plant communities in the Kouga‐Baviaanskloof region, an area within South Africa's Cape Floristic Region (CFR) containing high α and β diversity. This region contains strong climatic gradients and topographic heterogeneity, and is comprised of distinct vegetation classes with varying fire histories, making it an ideal location to assess the role of niche‐based environmental filtering on community composition by examining how traits vary with environment. We combined functional trait measurements for over 300 species with observations from vegetation surveys carried out in 1991/1992 and repeated in 2011/2012. We applied redundancy analysis, quantile regression, and null model tests to examine trends in species turnover and functional traits along environmental gradients in space and through time. Functional trait values were weakly associated with most spatial environmental gradients and only showed trends with respect to vegetation class and time since fire. However, survey plots showed greater compositional and functional stability through time than expected based on null models. Taken together, we found clear evidence for functional distinctions between vegetation classes, suggesting strong environmental filtering at this scale, most likely driven by fire dynamics. In contrast, there was little evidence of filtering effects along environmental gradients within vegetation classes, suggesting that assembly processes are largely neutral at this scale, likely the result of very high functional redundancy among species in the regional species pool.     

Data-driven identification of major axes of functional variation in bacteria

The discovery of major axes of correlated functional variation among species and habitats has revealed the fundamental trade-offs structuring both functional and taxonomic diversity in eukaryotes such as plants. Whether such functional axes exist in the bacterial realm and whether they could explain bacterial taxonomic turnover among ecosystems remains unknown. Here, we use a data-driven approach to leverage global genomic and metagenomic datasets to reveal the existence of major axes of functional variation explaining both evolutionary differentiation within Bacteria and their ecological sorting across diverse habitats. We show that metagenomic variation among bacterial communities from various ecosystems is structured along a few axes of correlated functional pathways. Similar clusters of traits explained phylogenetic trait variation among >16,000 bacterial genomes, suggesting that functional turnover among bacterial communities from distinct habitats does not only result from the differential filtering of similar functions among communities, but also from phylogenetic correlations among these functions. Concordantly, functional pathways associated with trait clusters that were most important for defining functional turnover among bacterial communities were also those that had the highest phylogenetic signal in the bacterial genomic phylogeny. This study overall underlines the important role of evolutionary history in shaping contemporary distributions of bacteria across ecosystems.     

High plant taxonomic beta diversity and functional and phylogenetic convergence between two Neotropical inselbergs

ABSTRACT

Background: Inselbergs (granitic and gneissic rock outcrops) are common elements in the Atlantic Forest and present large taxonomic (TD), functional (FD) and phylogenetic (PD) diversity.

Aims: We investigated how plant diversity changed across ecological and biogeographic scales by comparing TD, FD and PD of communities within and between two inselbergs. We expected converging FD and PD but distinct TD between outcrops, because of similar local environmental conditions in inselbergs and the long-term lineage isolation.

Methods: We calculated TD, PD and FD, and partitioned diversity into α (each inselberg), β (between inselbergs) and γ (whole sample) components. Phylogenetic signal was estimated for all traits. To link environmental predictors to functional traits a redundancy analysis was run. Variation in TD, FD and PD was analysed by general linear models with patch area and the two inselbergs as predictors.

Results: The inselbergs were taxonomically different, but showed convergence in their functional and phylogenetic diversity. The limited retention of phylogenetic signal suggests that different species may converge and respond similarly to environmental variables. Within inselbergs, larger patches displayed higher TD, FD and PD.

Conclusions: Seeking conservation strategies for inselbergs is challenging since, despite their functional and phylogenetic similarity, endemic species make individual rock outcrops unique.     

Ants of Three Adjacent Habitats of a Transition Region Between the Cerrado and Caatinga Biomes: The Effects of Heterogeneity and Variation in Canopy Cover

Habitat heterogeneity and complexity associated with variations in climatic conditions are important factors determining the structure of ant communities in different terrestrial ecosystems. The objective of this study was to describe the horizontal and vertical distribution patterns of the ant community associated with three adjacent habitats in a transition area between the Cerrado and Caatinga biomes at the Pandeiros River, state of Minas Gerais, Brazil. We tested the following hypotheses: (1) the richness and composition of ant species and functional group structure changes between different habitats and strata; (2) habitats with higher tree species richness and density support higher ant species richness; and (3) habitats with lower variation in canopy cover support higher ant species richness. Sampling was conducted in three adjacent habitats and at three vertical strata. Ant species richness was significantly different among vertical strata. Ant species composition was different among both habitats and vertical strata and functional group structure was divergent among habitats. Partitioning of the diversity revealed that the diversity for the three components was statistically different from the one expected by the null model; α and β ₂ were higher and β ₁ was lower than the values expected by chance. Tree density and variation in canopy cover negatively affected ant species richness. The occurrence of different species and the changing of functional group structures in different habitats and strata suggest an ecological–evolutionary relationship between ants and their habitats and emphasize the need to implement local conservation strategies in the ecotones between biomes.     

Plant Trait Variation along an Altitudinal Gradient in Mediterranean High Mountain Grasslands: Controlling the Species Turnover Effect

Assessing changes in plant functional traits along gradients is useful for understanding the assembly of communities and their response to global and local environmental drivers. However, these changes may reflect the effects of species composition (i.e. composition turnover), species abundance (i.e. species interaction), and intra-specific trait variability (i.e. species plasticity). In order to determine the relevance of the latter, trait variation can be assessed under minimal effects of composition turnover. Nine sampling sites were established along an altitudinal gradient in a Mediterranean high mountain grassland community with low composition turnover (Madrid, Spain; 1940 m–2419 m). Nine functional traits were also measured for ten individuals of around ten plant species at each site, for a total of eleven species across all sites. The relative importance of different sources of variability (within/between site and intra-/inter-specific functional diversity) and trait variation at species and community level along the considered gradients were explored. We found a weak individual species response to altitude and other environmental variables although in some cases, individuals were smaller and leaves were thicker at higher elevations. This lack of species response was most likely due to greater within- than between-site species variation. At the community level, inter-specific functional diversity was generally greater than the intra-specific component except for traits linked to leaf element content (leaf carbon content, leaf nitrogen content, δ¹³C and δ¹⁵N). Inter-specific functional diversity decreased with lower altitude for four leaf traits (specific leaf area, leaf dry matter content, δ¹³C and δ¹⁵N), suggesting trait convergence between species at lower elevations, where water shortage may have a stronger environmental filtering effect than colder temperatures at higher altitudes. Our results suggest that, within a vegetation type encompassing various environmental gradients, both, changes in species abundance and intra-specific trait variability adjust for the community functional response to environmental changes.     

片段化森林群落构建的生态过程及其检验方法

鉴于全球森林均呈现片段化(破碎化)的分布状态, 理解片段化森林群落构建的过程很有必要。该文通过综述群落构建的主要生态过程如生态漂变、扩散、选择和物种形成等在片段化森林群落构建中的相对作用, 发现因片段化森林形成方式的不同, 重构群落(片段化生境中通过次生演替重新形成的森林群落)和解构群落(原有森林被片段化后形成的森林群落)在不同演替阶段所受到的主要生态过程的相对作用有所不同。虽然利用基于群落内物种分布格局推测构建过程(如物种多度分布、零模型结合β多样性的方法、功能特征的收敛和发散等)、人工控制实验、群落结构动态分析等方法对片段化森林中群落构建的过程进行了有效的检验, 但是针对片段化森林群落构建过程的实验性研究仍然不足。未来有待在理论模型、群落构建过程的检验以及理论与物种保护相结合等方面继续开展深入的研究。     

Global to community scale differences in the prevalence of convergent over divergent leaf trait distributions in plant assemblages

Aim The drivers of species assembly, by limiting the possible range of functional trait values, can lead to either convergent or divergent distributions of traits in realized assemblages. Here, to evaluate the strengths of these species assembly drivers, we partition trait variance across global, regional and community scales. We then test the hypothesis that, from global to community scales, the outcome of co‐occurring trait convergence and divergence is highly variable across biomes and communities. Location Global: nine biomes ranging from subarctic highland to tropical rain forest. Methods We analysed functional trait diversity at progressively finer spatial scales using a global, balanced, hierarchically structured dataset from 9 biomes, 58 communities and 652 species. Analyses were based on two key leaf traits (foliar nitrogen content and specific leaf area) that are known to drive biogeochemical cycling. Results While 35% of the global variance in these traits was between biomes, only 15% was between communities within biomes and as much as 50% occurred within communities. Despite this relatively high within‐community variance in trait values, we found that trait convergence dominated over divergence at both global and regional scales through comparisons of functional trait diversity in regional and community assemblages against random (null) models of species assembly. Main conclusions We demonstrate that the convergence of traits occurring from global to regional assemblages can be twice as strong as that from regional to community assemblages, and argue that large differences in the nature and strength of abiotic and biotic drivers of dominant species assembly can, at least partly, explain the variable outcome of simultaneous trait convergence and divergence across sites. Ultimately, these findings stress the urgent need to extend species assembly research to address those scales where trait variance is the highest, i.e. between biomes and within communities.     

Plant functional and phylogenetic turnover correlate with climate and land use in the Western Swiss Alps

Aims Understanding the relative importance of historical and environmental processes in the structure and composition of communities is one of the longest quests in ecological research. Increasingly, researchers are relying on the functional and phylogenetic β-diversity of natural communities to provide concise explanations on the mechanistic basis of community assembly and the drivers of trait variation among species. The present study investigated how plant functional and phylogenetic β-diversity change along key environmental and spatial gradients in the Western Swiss Alps.Methods Using the quadratic diversity measure based on six functional traits—specific leaf area, leaf dry matter content, plant height, leaf carbon content, leaf nitrogen content and leaf carbon to nitrogen content alongside a species-resolved phylogenetic tree—we relate variations in climate, spatial geographic, land use and soil gradients to plant functional and phylogenetic turnover in mountain communities of the Western Swiss Alps.Important findings Our study highlights two main points. First, climate and land-use factors play an important role in mountain plant community turnover. Second, the overlap between plant functional and phylogenetic turnover along these gradients correlates with the low phylogenetic signal in traits, suggesting that in mountain landscapes, trait lability is likely an important factor in driving plant community assembly. Overall, we demonstrate the importance of climate and land-use factors in plant functional and phylogenetic community turnover and provide valuable complementary insights into understanding patterns of β-diversity along several ecological gradients.     

Partitioning taxonomic diversity of aquatic insect assemblages and functional feeding groups in neotropical savanna headwater streams

Biological diversity can be divided into: alpha (α, local), beta (β, difference in assemblage composition among locals), and gamma (γ, total diversity). We assessed the partitioning of taxonomic diversity of Ephemeroptera, Plecoptera and Trichoptera (EPT) and of functional feeding groups (FFG) in neotropical savanna (southeastern Brazilian cerrado) streams. To do so, we considered three diversity components: stream site (α), among stream sites (β₁), and among hydrologic units (β₂). We also evaluated the association of EPT genera composition with heterogeneity in land use, instream physical habitat structure, and instream water quality variables. The percentage of EPT taxonomic α diversity (20.7%) was smaller than the β₁ and β₂ diversity percentages (53.1% and 26.2%, respectively). The percentage of EPT FFG collector-gatherer α diversity (26.5%) was smaller than that of β₁ diversity (55.8%) and higher than the β₂ (17.7%) diversity. The collector-gatherer FFG was predominant and had the greatest β diversity percentage among stream sites (β₁, 55.8%). Our findings support the need for implementing regional scale conservation strategies in the cerrado biome, which has been degraded by anthropogenic activities.     

Using functional trait diversity to evaluate the contribution of multiple ecological processes to community assembly during succession

Successional chronosequences provide a unique opportunity to study the effects of multiple ecological processes on plant community assembly. Using a series of 0.5 × 0.5 m² plots (n = 30) from five successional sub‐alpine meadow plant communities (ages 3, 5, 9, 12, and undisturbed) in the Qinghai‐Tibetan Plateau, we investigated whether community assembly is stochastic or deterministic for species and functional traits. We tested directional change in species composition, functional trait composition, and then functional trait diversity measured by Rao's quadratic entropy for four traits – plant height, leaf dry matter content, specific leaf area, and seed mass – along two comparable successional chronosequences. We then evaluated the importance of species interactions, habitat filtering and stochasticity by comparing with random communities and partitioning the environmental and spatial components of Rao's quadratic entropy. We found no directional change in species composition, but clear directionality in functional trait composition. None of the abiotic environmental variables (except P) showed linear change with successional age, but soil moisture and nitrogen were positively related to functional diversity within meadows. Functional trait diversity increased significantly with the increase in successional age. Comparison with random communities showed a significant shift from trait divergence in early stages of succession (3‐ and 5‐yr) to convergence in the later stages of succession 9‐, 12‐yr and undisturbed). The relative importance of abiotic variables and spatial structure for functional trait diversity changed in a predictable manner with successional age. Stochasticity at the species level may indicate dispersal limitation, but deterministic effects on functional trait distributions show the role of both habitat effects and biotic interactions.