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AIM: Functional relationships between species groups on macroecological scales have often been inferred from comparisons of species numbers across space. On large spatial scales, however, it is difficult to assess whether correlations of species numbers represent actual functional relationships. Here, we investigated the functional relationship between a feeding guild (fruit‐eating birds) and its resource (fleshy‐fruited plants) by studying the matching of their functional traits across spatial scales, from individual interactions to regional patterns. LOCATION: A 3000‐m elevational gradient in the tropical Andes. METHODS: We sampled plant–bird interactions at two sites along the elevational gradient, and using multivariate statistics (fourth‐corner analysis) we identified corresponding morphological traits of birds and plants that influenced which bird species fed from which plant species. We then tested whether the functional trait diversities of the bird species assemblages matched those of the plant species assemblages along the elevational gradient. RESULTS: Corresponding functional traits of birds and plants were closely and significantly correlated on the scale of individual plant–bird interactions. On the regional scale, the functional diversities, but not species numbers, of bird and plant assemblages correlated significantly along the elevational gradient. MAIN CONCLUSIONS: The analysis of species interaction networks with multivariate statistics was a powerful tool for identifying relationships between functional traits of interacting species. The close functional relationships between birds and plants on the scale of individual interactions and on the regional scale show that comparisons of functional trait diversities, based on matching traits of interacting species, are better suited than correlations of species numbers to reveal the mechanisms behind large‐scale diversity patterns of interacting species. The identification of functional interdependences between interacting species on large spatial scales will be important for improving predictive models of species distributions in space and time.

Understanding how interspecific variation in functional traits influences species’ capacity to persist in fragments and use patches in fragmented landscapes is fundamental for the creation of effective conservation plans. This study uses phylogenetic comparative methods to investigate which functional traits of bat species are correlated with their vulnerability to fragmentation in a tropical landscape with low fragment–matrix contrast. Bats were captured over two years in eight forest fragments, nine control sites in continuous forest, and in the secondary forest matrix at the Biological Dynamics of Forest Fragments Project, Central Amazon, Brazil. We tested the hypothesis that there is a significant relationship between species functional traits, environmental gradients (continuous forest and fragment interiors, edges and matrix) and patterns of species distribution using phylogenetic generalized least squares (PGLS) models, as well as a combination of RLQ and fourth‐corner analyses. Mobility, body mass, wing morphology, and trophic level were the most important traits linked to fragmentation sensitivity based on the PGLS analysis, while body mass and trophic level emerged as the best predictors in the fourth‐corner analysis. These last two traits were correlated with the loss of continuous forest characteristics, such as high‐stature trees and forest cover. Many animalivorous bat species rarely persist in small fragments (<100 ha) and in the secondary forest matrix, reflecting strong effects of trait‐mediated environmental filters that selectively benefit the smaller and phytophagous species. Synthesis and applications. Functional traits of species and environmental variables jointly predict local variation in patterns of bat occupancy and abundance in fragmented tropical landscapes. To minimize local extinctions, we recommend increasing habitat availability and enhancing structural and functional connectivity at the landscape scale through the creation, restoration and maintenance of corridors and stepping stones. These measures should be coupled with improving matrix quality by promoting secondary forest regeneration and persistence to effectively reduce fragment–matrix contrast.

For the restoration of biodiversity in agricultural grasslands, it is essential to understand how management acts as an ecological filter on the resident species. Mowing constitutes such a filter: only species that possess functional traits enabling them to withstand its consequences can persist in the community. We investigated how the timing of mowing modulates this filtering effect for insects. We predicted that two traits drive species responses. Species with larval development within the meadow vegetation will suffer more from mowing than species whose larvae develop in or on the ground, or outside the meadows, while species with a later phenology should benefit from later mowing. We conducted a five-year experiment, replicated at 12 sites across the Swiss lowlands, applying three different mowing regimes to lowintensity hay meadows: (1) first cut of the year not earlier than 15 June (control regime); (2) the first cut delayed until 15 July; and (3) leaving an uncut grass refuge on 10–20% of the meadow area (after earliest first cut on 15 June). Before the first cut in years 4 or 5, we sampled larvae of Lepidoptera and sawflies, and adults of moths, parasitoid wasps, wild bees, hoverflies, ground beetles, and rove beetles. Overall, before the first cut of the year, abundances of species with vegetation-dwelling larvae were higher in meadows with delayed mowing or an uncut grass refuge, with some taxon-specific variation. In contrast, species whose larval development is independent of the meadow vegetation showed no differences in abundance between mowing regimes. Species richness did not differ among regimes. For species with vegetation-dwelling larvae, a fourth-corner analysis showed an association between early phenology and the control regime. No associations were found for the other functional groups. Our results show that slight modifications of mowing regimes, easily implementable in agri-environmental policy schemes, can boost invertebrate abundance, potentially benefitting insectivorous vertebrates.

The fourth-corner analysis aims to quantify and test for relationships between species traits and site-specific environmental variables, mediated by site-specific species abundances. Since there is no common unit of observation, the significance of the relationships is tested using a double permutation procedure (site based and species based). This method implies that all species and sites are independent of each other. However, this fundamental hypothesis might be flawed because of phylogenetic relatedness between species and spatial autocorrelation in the environmental data. Here, using a simulation-based experiment, we demonstrate how the presence of spatial and phylogenetic autocorrelations can, in some circumstances, lead to inflated type I error rates, suggesting that significant associations can be misidentified. As an alternative, we propose a new randomization approach designed to avoid this issue, based on Moran’s spectral randomization. In this approach, standard permutations are replaced by constrained randomizations so that the distribution of the statistic under the null hypothesis is built with additional constraints to preserve the phylogenetic and spatial structures of the observed data. The inclusion of this new randomization approach provides total control over type I error rates and should be used in real studies where spatial and phylogenetic autocorrelations often occur.

Biological control services of agroecosystems depend on the functional diversity of species traits. However, the relationship between arthropod traits and landscape heterogeneity is still poorly understood, especially in tropical rice agroecosystems, which harbor a high diversity of often specialized species. We investigated how landscape heterogeneity, measured by three metrics of landscape composition and configuration, influenced body size, functional group composition, dispersal ability, and vertical distribution of rice arthropods in the Philippines. We found that landscape composition and configuration acted to filter arthropod traits in tropical rice agroecosystems. Landscape diversity and rice habitat fragmentation were the two main gradients influencing rice-arthropod traits, indicating that different rice arthropods have distinct habitat requirements. Whereas small parasitoids and species mostly present in the rice canopy were favored in landscapes with high compositional heterogeneity, predators and medium-sized species occupying the base of the rice plant, including planthoppers, mostly occurred in highly fragmented rice habitats. We demonstrate the importance of landscape heterogeneity as an ecological filter for rice arthropods, identifying how the different components of landscape heterogeneity selected for or against specific functional traits. However, the contrasting effects of landscape parameters on different groups of natural enemies indicate that not all beneficial rice arthropods can be promoted at the same time when using a single land management strategy. Increasing compositional heterogeneity in rice landscapes can promote parasitoids but may also negatively affect predators. Future research should focus on identifying tradeoffs between fragmented rice habitats and structurally diverse landscapes to maximize the presence of multiple groups of beneficial arthropods.

Summary Immigration, extirpation and persistence of individual populations of species are key processes determining community responses to environmental change. However, they are difficult to study over long time periods without corresponding historical and modern‐day species occurrences. We used historical and present‐day plant species occurrence data from two different spatial scales (resolutions) to investigate the plant community turnover during the 20th century in a Baltic Sea archipelago. Patterns of turnover were analysed in relation to plant functional traits relating to dispersal and competition/persistence, as well as biogeographical variables. Turnover was largely driven by interactions between functional traits and measures of area, connectivity and distance to mainland. However, the combinations of traits and biogeographical variables that were most important for predicting immigration and extirpation differed between data sets, and between species associated with grassland management and the entire species pool. Taller plants were more likely to persist regardless of scale and biogeography, reflecting the grazing abandonment that occurred in the study area. Interactions between dispersal traits and biogeography were related to immigrations when the entire species pool was considered. However, increased dispersal potential, a smaller island size and increasing distance to mainland combined to promote extirpations in management‐associated species. A perennial life span and seed banking contributed to species persistence. At the larger spatial scale, trait‐driven turnover was not mediated by the biogeographical context. We showed that it is important to consider functional traits, biogeographical variables and their interactions when analysing community turnover over time. Furthermore, we found that the understanding of how combinations of traits and biogeography predict turnover depends on the source and spatial scale of the available data, and the species pool analysed. Lay Summary

Questions: Which plant traits consistently respond to grazing in different years and across habitat-related environmental heterogeneity? Does the proposed partial RLQ approach allow partitioning of grazing-related environmental parameters from other environmental and temporal variations? Location: Semi-arid savannas of central Namibia. Methods: We recorded nine quantitative and 12 categorical traits from 87 plant species along grazing gradients in semi-arid Namibian rangelands. We sampled from gradients in different habitat settings in 2 yr with differing total rainfall amounts. We first examined trait-environment relations with RLQ analysis. To remove confounding effects of temporal and habitat-related environmental variation on trait performance, we introduced a novel partial RLQ analysis approach. Furthermore, we used the fourth-corner statistic to quantify and test relations between traits, environmental factors and RLQ axes. Results: Habitats and years had strong influences on trait patterns. After removing environmental variation caused by habitats and years, grazing became the most influential factor on trait responses. Traits negatively correlated with increasing grazing pressure were common to perennial grasses, such as long and entire leaves, anemochorous dispersal and rhizomatous growth. Positively correlated traits were those common to herbaceous, annual plants with a prostrate-creeping habit, compound leaves, high specific leaf area (SLA) and exo-or endozoochorous dispersal. Some previously acknowledged grazing response traits, like growth form and plant height, were strongly influenced by variations in habitats and years and showed no significant correlation with grazing pressure. Conclusion: We emphasize that some traits that respond to grazing may also vary under different habitat conditions and among years, especially in highly variable environments like semi-arid savannas. When analysing trait-environment relations we recommend using approaches that partition environmental variation, particularly when applying broad sampling schemes at larger geographical scales.

Questions: (1) How do community-weighted mean (CWM) trait values of 23 functional traits measured on 34 plant species vary along a gradient of aridity under grazed and ungrazed conditions in an arid steppe? (2) How does variation in our CWM trait values differ from those of more mesic grasslands? Location: Eastern Morocco. Methods: We measured relative abundance and functional traits along a short aridity gradient over two consecutive years at five heavily grazed sites, each with an exclosure preventing grazing. We analysed the relationship between aridity, grazing, and the expression of CWM trait values using ordination methods and a fourth-corner analysis. Results: Unconstrained and constrained ordinations identified three distinct suites of temporally consistent functional traits that co-varied with aridity and grazing, and the fourth-corner analysis identified a number of significant but weak trait-environment associations. Grazing selected for short, fast-growing annual species with high SLA, high pastoral value and low seed mass, while aridity selected for species possessing succulent leaves with high δ¹³C leaf content, spines, low LDMC and short stature, although the relative importance of precipitation and grazing changed between years. Conclusions: Although distinct from more mesic grasslands, our study sites exhibited patterns of trait correlations that were similar to the worldwide leaf economics spectrum. These correlation patterns represented three groups that were reminiscent of Grime's C-S-R model. Direct ordinations supported this interpretation. Temporal variation in our results was due in part to precipitation fluctuations. Our results also indicated selection for a grazing avoidance strategy under heavy grazing. Integrating plant functional traits in conservation and management of arid ecosystems represents a novel and challenging task to ensure more sustainable use of these lands.

Tropical montane forests comprise heterogeneous environments along natural gradients of topography and elevation. Human‐induced edge effects further increase the environmental heterogeneity in these forests. The simultaneous effects of natural and human‐induced gradients on the functional diversity of plant leaf traits are poorly understood. In a tropical montane forest in Bolivia, we studied environmental gradients associated with elevation (from 1900 m to 2500 m asl), topography (ridge and gorge), and edge effects (forest edge vs. forest interior), and their relationship with leaf traits and resource‐use strategies. First, we investigated associations of environmental conditions (soil properties and microclimate) with six leaf traits, measured on 119 woody plant species. Second, we evaluated changes in functional composition with community‐weighted means and functional structure with multidimensional functional diversity indices (FRic, FEve and FDiv). We found significant associations between leaf traits and soil properties in accordance with the trade‐off between acquisition and conservation of resources. Functional composition of leaf traits shifted from the dominance of acquisitive species in habitats at low altitudes, gorges, and forest interior to the dominance of conservative species in habitats at high altitudes, ridges, and forest edges. Functional structure was only weakly associated with the environmental gradients. Natural and human‐induced environmental gradients, especially soil properties, are important for driving leaf traits and resource‐use strategies of woody plants. Nevertheless, weak associations between functional structure and environmental gradients suggest a high redundancy of functional leaf traits in this tropical montane forest.

Question: It is presumed that environmental stress is more pronounced at higher altitudes in Andean forests due to lower rates of temperature-constrained processes of growth, nutrient uptake and decomposition. Because community assembly theory predicts a low variation in viable traits under conditions of strong ecological filtering, we asked if the diversity in plant traits related to productivity and reproduction would decrease upslope. Location: Guaramacal National Park in the Andes of Venezuela (9°05-21′N, 70°-20′W). Methods: We studied altitudinal patterns in the number of trait states of seven categorical traits found among vascular plants (DBH ≥ 2.5 cm) in 35 0.1-ha plots between 1330 and 2890 m. Information on plant traits was obtained from literature and herbaria. To test the altitudinal correlations, we permuted the plot-to-species matrix by randomly selecting species from the entire species pool (conserving the species richness and the species—abundance pattern in each plot), applying no restrictions and by creating plot-wise null assemblages of species that most likely occurred near a particular plot. In addition, the altitudinal pattern of trait states was examined using fourth-corner analysis. Results: Both null model tests yielded similar results. The trait state diversity in fruit size decreased upslope. Plants with small fruits were mostly, but not exclusively, found at higher altitudes, whereas plants with large fruits occurred only at lower elevations. Leaf size showed more states at higher altitudes but this pattern disappeared when rare leaf size classes were down-weighted. The upslope decrease in fruit size might be explained by the relatively low tree height of the upper montane rain forests, the increased selection for large seeds at high temperatures downslope, and the upslope decrease of large-leaved taxa (in view of Corner's rule). Conclusions: The functional diversity of important plant traits changed with altitude at Guaramacal. Altitudinal effects on plant trait responses should be controlled for in studies that monitor the degradation of functional diversity in Andean forests in relation to human influence.