Explore the vast range of titles available.

Biodiversity is defined by trait differences between organisms, and biologists have long sought to predict associations among ecologically important traits. Why do some traits trade off but others are coexpressed? Why might some trait associations hold across levels of organization, from individuals and genotypes to populations and species, whereas others only occur at one level? Understanding such scaling is a core biological problem, bearing on the evolution of ecological strategies as well as forecasting responses to environmental change. Explicitly considering the hierarchy of biodiversity and expectations at each scale (individual change, evolution within and among populations, and species turnover) is necessary as we work toward a predictive framework in evolutionary ecology. Within species, a trait may have an association with another trait because of phenotypic plasticity, genetic correlation, or population-level local adaptation. Plastic responses are often adaptive and yet individuals have a fixed pool of resources; thus, positive and negative trait associations can be generated by immediate environmental needs and energetic demands. Genetic variation and covariation for traits within a population are typically shaped by varying natural selection in space and time. Although genetic correlations are infrequently long-term constraints, they may indicate competing organismal demands. Traits are often quantitatively differentiated among populations (local adaptation), although selection rarely favors qualitatively different strategies until populations become reproductively isolated. Across species, niche specialization to particular habitats or biotic interactions may determine trait correlations, a subset of which are termed “strategic trade-offs” because they are a consequence of adaptive specialization. Across scales, constraints within species often do not apply as new species evolve, and conversely, trait correlations observed across populations or species may not be reflected within populations. I give examples of such scale-dependent trait associations and their causes across taxonomic groups and ecosystems, and in the final section of the paper, I specifically evaluate leaf economics spectrum traits and their associations with plant defense against herbivory. Scale-dependent predictions emerge for understanding plant ecology holistically, and this approach can be fruitfully applied more generally in evolutionary ecology. Adaptive specialization and community context are two of the primary drivers of trade-offs and syndromes across biological scales.

Disturbance regimes are changing rapidly, and the consequences of such changes for ecosystems and linked social-ecological systems will be profound. This paper synthesizes current understanding of disturbance with an emphasis on fundamental contributions to contemporary landscape and ecosystem ecology, then identifies future research priorities. Studies of disturbance led to insights about heterogeneity, scale, and thresholds in space and time and catalyzed new paradigms in ecology. Because they create vegetation patterns, disturbances also establish spatial patterns of many ecosystem processes on the landscape. Drivers of global change will produce new spatial patterns, altered disturbance regimes, novel trajectories of change, and surprises. Future disturbances will continue to provide valuable opportunities for studying pattern-process interactions. Changing disturbance regimes will produce acute changes in ecosystems and ecosystem services over the short (years to decades) and long term (centuries and beyond). Future research should address questions related to (1) disturbances as catalysts of rapid ecological change, (2) interactions among disturbances, (3) relationships between disturbance and society, especially the intersection of land use and disturbance, and (4) feedbacks from disturbance to other global drivers. Ecologists should make a renewed and concerted effort to understand and anticipate the causes and consequences of changing disturbance regimes.

Metabolism provides a basis for using first principles of physics, chemistry, and biology to link the biology of individual organisms to the ecology of populations, communities, and ecosystems. Metabolic rate, the rate at which organisms take up, transform, and expend energy and materials, is the most fundamental biological rate. We have developed a quantitative theory for how metabolic rate varies with body size and temperature. Metabolic theory predicts how metabolic rate, by setting the rates of resource uptake from the environment and resource allocation to survival, growth, and reproduction, controls ecological processes at all levels of organization from individuals to the biosphere. Examples include: (1) life history attributes, including development rate, mortality rate, age at maturity, life span, and population growth rate; (2) population interactions, including carrying capacity, rates of competition and predation, and patterns of species diversity; and (3) ecosystem processes, including rates of biomass production and respiration and patterns of trophic dynamics. Data compiled from the ecological literature strongly support the theoretical predictions. Eventually, metabolic theory may provide a conceptual foundation for much of ecology, just as genetic theory provides a foundation for much of evolutionary biology.

Explicit consideration of timescales and dynamics is required for an understanding of fundamental issues in ecology. Endogenous dynamics can lead to transient states where asymptotic behavior is very different from dynamics on short timescales. The causes of these kinds of transients can be placed in one of three classes: linear systems with different timescales embedded or exhibiting reactive behavior, the potentially long times to reach synchrony across space for oscillating systems, and the complex dynamics of systems with strong density-dependent (nonlinear) interactions. It is also important to include the potentially disparate timescales inherent in ecological systems when determining the endogenous dynamics. I argue that the dynamics of ecological systems can best be understood as the response, which may include transient dynamics, to exogenous influences leading to the observed dynamics on ecologically relevant timescales. This view of ecosystem behavior as responses of ecological systems governed by endogenous dynamics to exogenous influences provides a synthetic way to unify different approaches to population dynamics, to understand mechanisms that determine the distribution and abundance of species, and to manage ecosystems on appropriate timescales. There are implications for theoretical approaches, empirical approaches, and the statistical approaches that bridge theory and observation.

The ecosystem concept has become a standard paradigm for studying ecological systems. Underlying the ecosystem concept is a \"machine analogy\" derived from Systems Analysis. This analogy is difficult to reconcile with our current understanding of ecological systems as metastable adaptive systems that may operate far from equilibrium. This paper discusses some logical and scientific problems associated with the ecosystem concept, and suggests a number of modifications in the paradigm to address these problems.