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Abstract Herbivory can affect the soil microbiome, creating legacies that affect plant resistance, but how these effects vary by feeding guild and the plant traits involved remain underexplored. We tested how soil legacies created by a leaf‐chewing caterpillar (Spodoptera exigua) and a sap‐feeding aphid (Aphis gossypii) influence resistance inBaccharis salicifoliaby evaluating changes in plant traits and soil microbial diversity.We conditioned soil with three herbivory treatments onB. salicifolia: caterpillar herbivory, aphid herbivory or control (no herbivory). Then, we grew new plants in sterile soil inoculated with 10% conditioned soil from each treatment and conducted resistance bioassays, measured plant nutritional and defence traits and analysed microbial diversity.Caterpillar, but not aphid herbivory, created legacies that affected resistance to both herbivores in opposite directions: plants in caterpillar‐conditioned soil had 16% smaller aphid colonies than plants in control soil, and a 76% increase in caterpillar performance relative to aphid‐conditioned soil, suggesting guild‐specific trade‐offs in resistance. These plants also showed a 12% higher carbon‐to‐nitrogen ratio than plants in control soil, mediating resistance to the aphid but not to the caterpillar. Herbivory did not affect microbial taxonomic diversity, suggesting shifts in microbiome biomass or function underlie the observed effects.Our findings highlight that herbivory‐induced soil legacies are guild‐specific and can alter plant resistance via trait‐mediated pathways, underscoring the importance of considering herbivore identity when evaluating above–below‐ground feedbacks. Read the freePlain Language Summaryfor this article on the Journal blog. 

ABSTRACT Differences in dominance are frequently invoked to explain the outcomes of competition. Yet, what it means to be dominant, and which traits underlie dominance, are poorly understood. Here, we sought to determine the relationships between multiple aspects of dominance, the potential for trade‐offs with discovery ability, and the traits associated with these patterns within a high elevation community of five ant taxa. We examined several common dominance metrics—behavioral dominance (winning aggressive encounters at both the individual and colony levels), numerical dominance (abundance and activity in baits and pitfall traps), and ecological dominance (high relative frequency in baits)—and found that individual‐ and colony‐level behavioral dominance was positively correlated, as were ecological and numerical dominance. However, colony‐level behavioral and numerical dominance were negatively correlated, and no other dominance metrics were associated. There was a dominance‐discovery trade‐off, as increased behavioral (but not numerical or ecological) dominance was associated with slower resource discovery. This trade‐off was likely driven by behaviorally dominant ants having larger body sizes and recruiting a greater biomass of workers to baits. In contrast, fast discoverers were more abundant in the environment (i.e., numerically dominant). Complementing our empirical study, a meta‐analysis of 54 responses from 21 studies showed that the association between dominance and discovery ability depended on the dominance metric. Whereas discovery ability was positively correlated with numerical dominance, its relationships with behavioral and ecological dominance were highly variable and not significantly different from zero. Overall, our empirical findings, in combination with the synthesis of past studies, demonstrate that different aspects of ant dominance are not equivalent. Yet, regardless of dominance type, there is little evidence that dominance‐discovery trade‐offs occur in most ant communities. 

Abstract PremisePrevious studies have suggested a trade‐off between trichome density (D_t) and stomatal density (D_s) due to shared cell precursors. We clarified how, when, and why this developmental trade‐off may be overcome across species. MethodsWe derived equations to determine the developmental basis forD_tandD_sin trichome and stomatal indices (i_tandi_s) and the sizes of epidermal pavement cells (e), trichome bases (t), and stomata (s) and quantified the importance of these determinants ofD_tandD_sfor 78 California species. We compiled 17 previous studies ofD_t–D_srelationships to determine the commonness ofD_t–D_sassociations. We modeled the consequences of differentD_t–D_sassociations for plant carbon balance. ResultsOur analyses showed that higherD_twas determined by higheri_tand lowere, and higherD_sby higheri_sand lowere. Across California species, positiveD_t–D_scoordination arose due toi_t–i_scoordination and impacts of the variation ine. AD_t–D_strade‐off was found in only 30% of studies. Heuristic modeling showed that species sets would have the highest carbon balance with a positive or negative relationship or decoupling ofD_tandD_s, depending on environmental conditions. ConclusionsShared precursor cells of trichomes and stomata do not limit higher numbers of both cell types or drive a generalD_t–D_strade‐off across species. This developmental flexibility across diverse species enables differentD_t–D_sassociations according to environmental pressures. Developmental trait analysis can clarify how contrasting trait associations would arise within and across species. 

Abstract Tree diversity can promote both predator abundance and diversity. However, whether this translates into increased predation and top‐down control of herbivores across predator taxonomic groups and contrasting environmental conditions remains unresolved. We used a global network of tree diversity experiments (TreeDivNet) spread across three continents and three biomes to test the effects of tree species richness on predation across varying climatic conditions of temperature and precipitation. We recorded bird and arthropod predation attempts on plasticine caterpillars in monocultures and tree species mixtures. Both tree species richness and temperature increased predation by birds but not by arthropods. Furthermore, the effects of tree species richness on predation were consistent across the studied climatic gradient. Our findings provide evidence that tree diversity strengthens top‐down control of insect herbivores by birds, underscoring the need to implement conservation strategies that safeguard tree diversity to sustain ecosystem services provided by natural enemies in forests. 

Abstract The relationship between stomatal traits and environmental drivers across plant communities has important implications for ecosystem carbon and water fluxes, but it has remained unclear. Here, we measure the stomatal morphology of 4492 species-site combinations in 340 vegetation plots across China and calculate their community-weighted values for mean, variance, skewness, and kurtosis. We demonstrate a trade-off between stomatal density and size at the community level. The community-weighted mean and variance of stomatal density are mainly associated with precipitation, while that of stomatal size is mainly associated with temperature, and the skewness and kurtosis of stomatal traits are less related to climatic and soil variables. Beyond mean climate variables, stomatal trait moments also vary with climatic seasonality and extreme conditions. Our findings extend the knowledge of stomatal trait–environment relationships to the ecosystem scale, with applications in predicting future water and carbon cycles. 

Abstract Allometric relationships among the dimensions of leaves and their cells hold across diverse eudicotyledons, but have remained untested in the leaves of grasses. We hypothesised that geometric (proportional) allometries of cell sizes across tissues and of leaf dimensions would arise due to the coordination of cell development and that of cell functions such as water, nutrient and energy transport, and that cell sizes across tissues would be associated with light‐saturated photosynthetic rate. We tested predictions across 27 globally distributed C₃and C₄grass species grown in a common garden. We found positive relationships among average cell sizes within and across tissues, and of cell sizes with leaf dimensions. Grass leaf anatomical allometries were similar to those of eudicots, with exceptions consistent with the fewer cell layers and narrower form of grass leaves, and the specialised roles of epidermis and bundle sheath in storage and leaf movement. Across species, mean cell sizes in each tissue were associated with light‐saturated photosynthetic rate per leaf mass, supporting the functional coordination of cell sizes. These findings highlight the generality of evolutionary allometries within the grass lineage and their interlinkage with coordinated development and function. 

Abstract Improved estimation of climate niches is critical, given climate change. Plant adaptation to climate depends on their physiological traits and their distributions, yet traits are rarely used to inform the estimation of species climate niches, and the power of a trait‐based approach has been controversial, given the many ecological factors and methodological issues that may result in decoupling of species' traits from their native climate.For 107 species across six ecosystems of California, we tested the hypothesis that mechanistic leaf and wood traits can robustly predict the mean of diverse species' climate distributions, when combining methodological improvements from previous studies, including standard trait measurements and sampling plants growing together at few sites. Further, we introduce an approach to quantify species' trait‐climate mismatch.We demonstrate a strong power to predict species mean climate from traits. As hypothesized, the prediction of species mean climate is stronger (and mismatch lower) when traits are sampled for individuals closer to species' mean climates.Improved resolution of species' climate niches based on mechanistic traits can importantly inform conservation of vulnerable species under the threat of climatic shifts in upcoming decades. Read the freePlain Language Summaryfor this article on the Journal blog. 

Abstract The diversity of specialized molecules produced by plants radiating along ecological gradients is thought to arise from plants' adaptations to local conditions. Therefore, closely related species growing in similar habitats should phylogenetically converge, or diverge, in response to similar climates, or similar interacting animal communities. We here asked whether closely related species in the genusHaplopappus(Asteraceae) growing within the same elevation bands in the Andes, converged to produce similar floral odors. To do so, we combine untargeted analysis of floral volatile organic compounds with insect olfactory bioassay in congenericHaplopappus(Asteraceae) species growing within the same elevation bands along the Andean elevational gradient. We then asked whether the outcome of biotic interactions (i.e., pollination vs. seed predation) would also converge across species within the same elevation. We found that flower odors grouped according to their elevational band and that the main floral visitor preferred floral heads from low‐elevation band species. Furthermore, the cost–benefit ratio of predated versus fertilized seeds was consistent within elevation bands, but increased with elevation, from 6:1 at low to 8:1 at high elevations. In the light of our findings, we propose that climate and insect community changes along elevation molded a common floral odor blend, best adapted for the local conditions. Moreover, we suggest that at low elevation where floral resources are abundant, the per capita cost of attracting seed predators is diluted, while at high elevation, sparse plants incur a higher herbivory cost per capita. Together, our results suggest that phytochemical convergence may be an important factor driving plant–insect interactions and their ecological outcomes along ecological gradients. 

Global change is causing unprecedented degradation of the Earth’s biological systems and thus undermining human prosperity. Past practices have focused either on monitoring biodiversity decline or mitigating ecosystem services degradation. Missing, but critically needed, are management approaches that monitor and restore species interaction networks, thus bridging existing practices. Our overall aim here is to lay the foundations of a framework for developing network management, defined here as the study, monitoring, and management of species interaction networks. We review theory and empirical evidence demonstrating the importance of species interaction networks for the provisioning of ecosystem services, how human impacts on those networks lead to network rewiring that underlies ecosystem service degradation, and then turn to case studies showing how network management has effectively mitigated such effects or aided in network restoration. We also examine how emerging technologies for data acquisition and analysis are providing new opportunities for monitoring species interactions and discuss the opportunities and challenges of developing effective network management. In summary, we propose that network management provides key mechanistic knowledge on ecosystem degradation that links species- to ecosystem-level responses to global change, and that emerging technological tools offer the opportunity to accelerate its widespread adoption.