Ecology Letters最新文献

Mitchell, E. G., Harris, S., Kenchington, C. G., Vixseboxse, P., Roberts, L., Clark, C., Dennis, A., Liu, A. G., & Wilby, P. R. 2019. “ The importance of neutral over niche processes in structuring Ediacaran early animal communities.” Ecology letters 22: 2028–2038. https://doi.org/10.1111/ele.13383.

In the above published article, the authors have spotted an error in Table 2: the Mean number in the cluster column is a replicate of the previous column and does not reflect the correct results. The correct version of the table is shown below.

We apologize for this error.

Experiments have long been the gold standard for causal inference in Ecology. As Ecology tackles progressively larger problems, however, we are moving beyond the scales at which randomised controlled experiments are feasible. To answer causal questions at scale, we need to also use observational data —something Ecologists tend to view with great scepticism. The major challenge using observational data for causal inference is confounding variables: variables affecting both a causal variable and response of interest. Unmeasured confounders—known or unknown—lead to statistical bias, creating spurious correlations and masking true causal relationships. To combat this omitted variable bias, other disciplines have developed rigorous approaches for causal inference from observational data that flexibly control for broad suites of confounding variables. We show how ecologists can harness some of these methods—causal diagrams to identify confounders coupled with nested sampling and statistical designs—to reduce risks of omitted variable bias. Using an example of estimating warming effects on snails, we show how current methods in Ecology (e.g., mixed models) produce incorrect inferences due to omitted variable bias and how alternative methods can eliminate it, improving causal inferences with weaker assumptions. Our goal is to expand tools for causal inference using observational and imperfect experimental data in Ecology.

With many species interacting in nature, determining which interactions describe community dynamics is nontrivial. By applying a computational modeling approach to an extensive field survey, we assessed the importance of interactions from plants (both inter- and intra-specific), pollinators and insect herbivores on plant performance (i.e., viable seed production). We compared the inclusion of interaction effects as aggregate guild-level terms versus terms specific to taxonomic groups. We found that a continuum from positive to negative interactions, containing mostly guild-level effects and a few strong taxonomic-specific effects, was sufficient to describe plant performance. While interactions with herbivores and intraspecific plants varied from weakly negative to weakly positive, heterospecific plants mainly promoted competition and pollinators facilitated plants. The consistency of these empirical findings over 3 years suggests that including the guild-level effects and a few taxonomic-specific groups rather than all pairwise and high-order interactions, can be sufficient for accurately describing species variation in plant performance across natural communities.

Phenotypic plasticity enables organisms to express a phenotype that is optimal in their current environment. The ability of organisms to obtain the optimum phenotype is determined by their (i) capacity for plasticity, which facilitates phenotypic adjustment corresponding to the amplitude of environmental change but also their (ii) rate of plasticity, because this determines if the expressed phenotype lags behind changes in the optimum. How the rate of- and capacity for plasticity have co-evolved will thus be critical for the resilience of organisms under different patterns of environmental change. To evaluate the direction of the evolved relationship between plasticity rate and capacity, we reanalysed experiments documenting the time course of thermal tolerance acclimation to temperature change across species of ectothermic animals. We found that the rate and capacity with which thermal tolerance responds plastically to temperature change are negatively correlated, a pattern inconsistent with current theory regarding the evolution of phenotypic plasticity.

Trees affect organic matter decomposition through allocation of recently fixed carbon belowground, but the magnitude and direction of this effect may depend on substrate type and decomposition stage. Here, we followed mass loss, chemical composition and fungal colonisation of leaf and root litters incubated in mountain birch forests over 4 years, in plots where belowground carbon allocation was severed by tree girdling or in control plots. Initially, girdling stimulated leaf and root litter mass loss by 12% and 22%, respectively, suggesting competitive release of saprotrophic decomposition when tree-mediated competition by ectomycorrhizal fungi was eliminated (Gadgil effect). After 4 years, girdling instead hampered mass loss of root litter by 30%, suggesting late-stage priming of decomposition in the presence of trees, in parallel with increased growth of shrubs and associated fungi following tree elimination. Hence, different mechanisms driving early- and late-stage litter decomposition should be considered in climate-feedback evaluations of plant–soil interactions.

Biotic interactions play an important role in species diversification and maintenance and, thus, are regarded as the architecture of biodiversity. Since Darwin and Wallace, biologists have debated whether biotic interactions are stronger towards the tropics and on continents, when compared to temperate regions and islands. Here, based on 354 avian frugivory networks accounting for 22,199 interactions between 1247 bird species and 2126 plant species, we quantified trait matching strength, which reflects interaction strength and specificity, across gradients of latitude and insularity globally. We found that matching between beak size and fruit size was significantly stronger towards the poles and on continents, when compared with the tropics and on islands. As underlining ecological factors, trait matching was stronger with a larger proportion of frugivory (measured as the mean proportion of fruits in bird diets) and network-level mean beak size, and with a smaller proportion of fleshy-fruited species (measured as the proportion of fleshy-fruited plant species in the botanical country where the network was located). These findings suggest that the latitudinal and insular patterns in trait matching are driven by biotic factors that may relate to trait co-evolution between interacting species and optimal foraging for bird species.