Global trait axes reveal overarching dimensions of plant functional variation. However, how these dimensions are spatially organized within and across forest types remains unclear. We combined drone-based full-range imaging spectroscopy with crown-level measurements of 16 physiological, morphological and biochemical traits across temperate, subtropical and tropical forests in China to enable spatially-explicit trait mapping. Through site-training scenario, leaf-to-canopy scaling and spectral-domain modelling tests, we find that reliable canopy trait retrieval depends not only on trait and spectral coverage, but also on preserving trait-spectral relationships across sites and scales. Spectral predictions recovered observed multivariate covariation, summarizing crown variation into a leaf-economics dimension and two additional biochemical dimensions related to hydro-thermal regulation and defence/metabolism. Mapping these dimensions revealed distinct community-level trait organization alongside substantial species- and crown-level variation within forests. These findings link remotely sensed trait retrieval to environmental filtering and plant functional differentiation, providing a scalable framework for monitoring forest functional diversity.
Meta-analyses in ecology and evolution sometimes target the magnitude of differences between groups rather than their direction, for example, when the question concerns deviation from a biological optimum or divergence from a reference state. A common practice is to convert signed effects into magnitudes by taking absolute values, but this can induce upward distortion and non-normal sampling distributions under standard meta-analytic models. Here we introduce lnM, a log-ratio effect size for the magnitude of difference between two groups, defined from one-way ANOVA components. lnM is asymptotically normal, supports standard multilevel meta-analysis and meta-regression and applies to both ratio- and interval-scale traits. Using theory, simulations and worked examples, we show when delta-method and single-fit bootstrap estimators perform well, and how lnM can be used to assess publication bias.
Crop diversification is a promising strategy to strengthen pest control services in agricultural landscapes. Diversifying crops may limit pests through host crop dilution or by enhancing top-down control by their enemies. However, crop diversification may also benefit generalist pests through higher resource continuity. Using a large-scale dataset encompassing 742 landscapes across 13 countries, we assessed the impact of landscape-scale crop diversity on the abundance of natural enemies, the potential for biological control, and insect pest abundance. Crop diversification did not increase the overall abundance of natural enemies or the potential for biological pest control. Instead, crop diversity primarily favoured the abundance of specialist natural enemies and pests in highly simplified landscapes, an effect that was reduced in landscapes with high proportions of semi-natural habitats. Lastly, low proportions of host crops in the landscape were associated with higher abundances of natural enemies. Taken together, our results indicate that crop diversification is not a 'one size fits all' strategy to control agricultural pests, and that other landscape characteristics, such as high amounts of semi-natural habitats, must be considered to enhance biological pest control services.
Among global changes, urbanisation entangles a variety of human-induced rapid environmental changes, such as habitat fragmentation, temperature change, introduction of human food sources and pollution. Urban environments in contrast to non-urban ones are often assumed to be more heterogeneous and variable in space and time. A key feature of animals coping with high environmental variability ought to be phenotypic flexibility, that is, the capacity of individuals to express reversible variation in labile traits. However, this 'phenotypic flexibility hypothesis' has not been tested rigorously. We compiled available raw data and used a meta-analysis to estimate overall differences in among- and within-individual variation between urban and non-urban population pairs of wild animals. We considered within-individual variation as a proxy of phenotypic flexibility. Across all taxa, among-individual variation did not differ between urban and non-urban populations. Within-individual variation was marginally lower in urban populations compared to non-urban ones. The potential decrease of phenotypic flexibility in urban individuals could result from the multidimensionality and complexity of urban environmental conditions. Overall, the effects of urbanisation on phenotypic variation are not generalisable and depend on the taxa, species, and traits. Future studies should increase efforts to directly link temporal and spatial environmental variability with phenotypic individual variation.
Agricultural intensification has led to many environmentally degrading practices that can cause insect biodiversity loss and a decline in ecosystem services. Local management practices and more complex landscapes can help mitigate these negative effects. The intermediate landscape complexity hypothesis suggests that local management best supports insect biodiversity in landscapes of intermediate complexity, which contain both agricultural and natural habitats. However, recent studies have also shown higher biodiversity in both simple and complex landscapes. In this review, we investigated whether certain local practices are more effective across a range of landscape complexity. Our results showed that local management or landscape complexity increases insect biodiversity or ecosystem services in about 25% of cases. We found support for the intermediate landscape complexity hypothesis in some scenarios and positive effects of local management in simple and complex landscapes in others. Future studies should more clearly define how they measure landscape complexity, which will help compare results and find patterns. These findings can begin to inform tailored local management and research directions to maximize insect biodiversity and ecosystem services in different landscape contexts.
Climate change affects the thermal environment in complex ways, including changing its temporal autocorrelation structure and intensifying heatwave regimes. While theory shows that higher temporal autocorrelation may exacerbate extinction risks, little work has been done to incorporate autocorrelation into thermal performance-based forecasting. Here, we pair stochastic simulation models of population dynamics with systematically generated temperature time series to determine when increasing the temporal autocorrelation of variable thermal environments generates greater extinction risks. We show that by clustering stressful conditions, increasing autocorrelation reduces the extent of warming and variability which populations with unimodal thermal tolerance can survive. We validate our predictions with a factorial experiment in protist microcosms, where we find that higher autocorrelation significantly elevates extinction risk across mean temperature treatments when environments include stressful temperatures. Taken together, these results provide the foundation for predicting which species and environments face the greatest thermal risks under increasing autocorrelation.
Schweiger and Schweiger (2024) recently proposed that the evolution of greater photosynthetic capacity in C 3 plant species may be linked to increased species diversification. This conclusion is premature because their methods cannot reliably estimate diversification rates or ancestral trait values. Reanalyzing the data set using model‐based phylogenetic comparative methods reveals no evidence that photosynthetic capacity is associated with diversification rates among C 3 plant genera.
The CO 2 ‐fertilisation effect (CFE) on vegetation productivity is the major driver of the enhanced land carbon sink in recent decades. CFE theoretically increases with elevation due to the higher sensitivity of carboxylation to an increase of CO 2 under lower CO 2 partial pressure, but the elevation‐dependent CFE pattern has been largely overlooked. By conducting a 6‐year CO 2 enrichment experiment (+100 ppm) in an alpine grassland, we show that elevated CO 2 increased gross primary production (GPP) by 25.5% ± 4.6%. Water availability and plant biomass allocation modulates CFE during different seasons. A global synthesis of 10 CO 2 enrichment experiments reveals that CFE increased with elevation. The satellite‐based EC‐LUE model also demonstrates a positive global elevation‐dependent CFE pattern, albeit substantially weaker than that from experimental observations. Current terrestrial biosphere models, however, could not represent the elevation‐dependent pattern, highlighting the need to improve the representations of plants' elevational physiological adaptation to rising CO 2 in models.
We utilized a long-term study of Weddell seals to compute lifetime reproductive success (LRS) distributions using a theoretical approach and an empirical approach. These comparisons are often difficult to achieve among natural populations but are important for disentangling sources of variation in lifetime measures. We performed three independent analyses: the first compared LRS and age-at-death distributions among populations living under different environmental conditions, the second focused on populations differing in individual heterogeneity (i.e., high or low reproductive strategy), and the third compared a theoretical LRS distribution with an empirical LRS distribution. Iceberg conditions increased the probability of LRS = 0 while individual heterogeneity had little influence on LRS distributions. Age-at-death distributions were also highly skewed and only early life mortality was affected by environmental condition. Our theoretical LRS distribution was strikingly similar to the empirical distribution estimated from females experiencing natural intrinsic trait variability and extrinsic environmental variability. We also examine inequality measures which show that females must be 'lucky' to survive past maturity and of those who do, only 74% breed. These findings contribute to ongoing research that reveals how diversity in lifetime outcomes is largely governed by chance alone.
Flowering time underpins plant fitness, species coexistence, and ecosystem functioning. While global warming consistently advances flowering, the influence of water availability remains unclear. We hypothesized that this inconsistency reflects the overlooked timing of drought. In 200 experimental Mediterranean annual-plant communities, we imposed autumn, winter, and spring dry periods and grew plants in monocultures and mixtures to disentangle physiological and competition-mediated responses. Dry autumn and spring shortened flowering duration: dry autumn delayed onset, dry spring advanced termination. Some shifts were direct; others emerged through competition. A new community-level index revealed greater phenological segregation in mixtures, showing that plasticity alone can generate niche separation under competition. Both dry autumn and spring tended to further enhance this segregation. Together, our results demonstrate that the seasonal timing of drought governs flowering responses through both direct physiological pathways and indirect biotic interactions, emphasizing rainfall seasonality as a key driver of ecological responses to climate change.
Higher-order interactions (HOIs) are widely predicted to promote coexistence, yet the underlying ecological mechanisms behind this effect remain largely unexplored in natural communities. Here, we integrate natural history and theory to show how HOIs can restructure competitive networks and influence coexistence. With over 2 years of data on a tropical ant community, we estimate pairwise competitive interactions and demonstrate that, in isolation, they fail to recreate observed community dynamics. We find that inclusion of an HOI, imposed by a parasitoid of the dominant species, can theoretically reorganize competitive networks to mirror the dynamics of the empirical system. We demonstrate how temporal variation in HOIs forces the community between dominance regimes and that the interregnum between regimes is riddled with competitive intransitivities that promote coexistence. This work provides an empirical example of the ecological mechanisms behind the coexistence-promoting effects of HOIs and suggests that HOIs and intransitivity, which are typically treated separately, can be mechanistically linked through the rewiring of species interactions.
The evolutionary imbalance hypothesis predicts that species from ecologically stable regions of high genetic potential and intense competition are more likely to be invasive, while regions with the opposite characteristics are more likely to be invasible. Relative phylogenetic diversity (PD) of species' indigenous ranges could indicate evolutionary imbalance and help identify high-risk invaders and vulnerable communities. We tested this with three seed addition experiments where 166 species of varying origins were sown into disturbed and undisturbed grassland plots. Species with high relative indigenous-PD had high colonisation and first-year survival regardless of disturbance, whereas species with low relative indigenous-PD only colonised disturbed communities and at a lower rate. Species' indigenous-PD did not appear to affect second-year survival. Although long-term outcomes are unknown, evidence suggests that species with high relative indigenous-PD pose a high invasion risk, even to intact communities. Regional PD could help indicate species invasiveness and community invasibility, informing biosecurity.
Impacts of environmental change on ecosystems are seemingly highly context-dependent and contingent on details. Here, we provide mathematical and numerical evidence that there is some generality to the resistance of food webs to species loss. To this end, we mathematically analyse simple food web models, run simulations with randomly wired food webs, develop a spatially explicit meta-community model for realistic macroinvertebrate communities inhabiting European streams, and analyse field data. These approaches jointly support three general rules for food web resistance: (1) all else equal, predators are more vulnerable than prey, and predator diversity declines before prey diversity; (2) food webs with higher prey diversity tend to be less resistant to environmental change; and (3) food web resistance decreases with the mean taxon tolerance and reaches a maximum at an optimal ratio of predator to prey tolerance. Our findings elucidate characteristics that make food webs vulnerable, fostering more effective conservation practices.
Niche overlap (NO) is a cornerstone of coexistence theory, summarising the strength of competitive coupling among species. Yet NO collapses distinct mechanisms into a single value and may miss key dynamical features. We quantify this limitation by examining temporal correlations in species abundances, a key out-of-equilibrium observable in microbial ecology. Using a MacArthur-type consumer-resource model, we show that communities with identical NO can display opposite dynamical patterns. Within the resource-mediated fluctuation regime studied here, a yield-depletion mismatch (YDM)-the difference between depletion and yield dissimilarities-consistently predicts the sign and magnitude of abundance correlations across analytical approximations, stochastic simulations, and a reanalysis of microbial time series. In contrast, growth-rate correlations are governed by NO. More broadly, our results show that dynamical observables can depend on mechanistic details beyond those summarised by niche overlap.
When and how much plants grow under environmental constraints are fundamental questions in biology and increasingly important for predicting biomass production and carbon sequestration under climate change. While temperature and water availability directly regulate plant growth, the timing and rate of growth are also shaped by internal developmental programming, though this is rarely considered in predictions of tree growth responses to future climates. Here, we revisit a concept central to this internal programming-(in)determinacy. Focusing on woody plants, we define it as the extent to which annual shoot growth is deployed from preformed organs versus produced de novo during the current season. We argue that this trait is best understood as a continuum and that it can help explain contrasting growth responses in a changing climate. More determinate species concentrate growth within a narrow seasonal window, which may reduce exposure to late-season stress but also limit their ability to exploit longer growing seasons. More indeterminate species retain greater flexibility to extend or resume growth when conditions remain favourable, which may be advantageous under climate change, but this same flexibility may also increase exposure to frost, drought and incomplete tissue maturation. Because primary shoot growth also shapes canopy development and is linked to other growth processes, variation in (in)determinacy could help explain broader differences in whole-plant performance, carbon gain and species responses to climate change.
Biological communities follow a remarkably consistent negative relationship between individual mass (M) and abundance (N), represented by a power law (N ~ Mλ). The parameter λ denotes the rate of decline in relative abundance from small to large individuals and serves as a proxy for energy transfer efficiency in food webs. Although warming is expected to affect λ, its influence remains uncertain, possibly due to interactions with resource supply. Using ~670,000 individual body sizes from stream food webs, we tested how temperature and resources shape λ. Temperature effects depended on resource supply (gross primary production [GPP] and organic matter standing stock [OM]) but contradicted expectations that λ becomes more negative with warming. At medium and high resources, λ becomes less negative under warming while no change occurred at low resources. Variation in OM, not GPP, drove these patterns, highlighting the role of external energy inputs and challenging the idea that large organisms are rarer at higher temperatures.
Speciation is the ultimate source of biodiversity, yet because most species arise in spatial isolation (allopatry), it remains unclear how speciation history shapes patterns of sympatric species richness. Here, we examine how the timing of past speciation events influences the maximum sympatric species richness attained across 40 families of passerine birds. Using a phylogenetic model, we infer that the average waiting time for species to assemble in sympatry is remarkably long (~8 million years), occurring over macroevolutionary timescales comparable to the pace of speciation itself. Consequently, we find that the proportion of species in sympatry varies substantially across families, peaking in ancient or small clades comprised of older species, while remaining low in large, rapidly diversifying clades. Our analysis shows that macroevolutionary delays in colonisation are sufficient for speciation history to leave an indelible legacy on present-day assemblages, challenging the view that richness is strictly limited by contemporary environmental capacity.
The species-area relationship is a cornerstone of biodiversity theory and conservation. Yet, its temporal stability remains largely untested. Using nearly a century of disjunct vegetation-plot data from the Netherlands, we assess changes in the species-area relationship by constructing species-accumulation curves (SACs). We show that SACs have flattened significantly over time, indicating widespread biodiversity decline driven by habitat degradation and spatial homogenization, even within protected areas. Although grassland biodiversity has rebounded, forest biodiversity continues to decline, suggesting a greater extinction debt. These findings provide unprecedented evidence that biodiversity patterns captured by SACs shift over time. They also reveal a critical limitation of conservation strategies that rely solely on protected area expansion. As global biodiversity goals aim to halt biodiversity loss by 2030, our results emphasise the need for adaptive conservation strategies that integrate area-based protection with large-scale habitat restoration and improved ecosystem management.
Tree species richness-productivity relationships (SPRs) at community level are generally positive but can weaken at individual levels due to increased competition. Using 12 years of growth data from a large forest biodiversity experiment, we examined effects of neighbourhood tree species richness, basal area, and niche differences on focal tree growth over time. As stands aged, the effect of greater neighbourhood basal area in more species-rich neighbourhoods on focal tree growth shifted from positive to negative, but this negative effect was offset by increasingly positive effects arising from greater niche differentiation between focal trees and their neighbours. Focal trees with acquisitive traits showed stronger growth responses to neighbourhood competition and niche difference; while the responses to neighbourhood richness were more positive in dry than in wet years. Our findings suggest that larger niche differences can balance increased competition in more species-rich forest stands, thus allowing these stands to maintain a greater total biomass than less diverse forest stands.
