Ecology Letters最新文献

Metacommunity Theory is among the most widely used theoretical frameworks in empirical community ecology. A central assumption of this framework is that individuals are structured into local communities, which collectively form the metacommunity. Thus, the concept of the local community is fundamental for connecting empirical observations with theoretical predictions. However, through a literature review, we show that most empirical studies conceptualised within Metacommunity Theory lack explicit spatial definitions of local communities. Among those that do, few provide ecological justification. We argue that this mismatch between theoretical assumptions and empirical practice hinders the interpretability and comparability of empirical results. To address this gap, we propose three alternative approaches for delineating local communities. These are based on whether conspecific and heterospecific individuals overlap in their space-use, interact with each other or have reciprocal fitness effects. Using agent-based simulations, we show how these three definitions may result in different delineations of local communities and that local communities do not necessarily form discrete units. To align empirical studies with Metacommunity Theory, we urge ecologists to explicitly define what spatial units they conceptualise as local communities. We also offer guidelines on what complementary data could be collected to achieve ecologically justified delineations of local communities.

A central goal in ecology is to understand the mechanisms shaping community assembly at different spatial and temporal scales. This knowledge is crucial for improving conservation strategies, but remains limited for ephemeral habitats. We investigated the contribution of environmental, that is, physical and chemical microhabitat properties, and spatial factors in shaping taxonomic and functional β-diversity of macroinvertebrate metacommunities inhabiting water-filled tree holes (WTHs) in forests in three biogeographical regions: Temperate-Mediterranean (France), Neotropical (Brazil), and Palaeotropical (India). We conducted standardised surveys of 35 WTHs per region on 100 ha plots. Spatial factors had a stronger effect on taxonomic and functional β-diversity than environmental properties. Species richness differences dominated taxonomic β-diversity. Processes driving functional β-diversity showed biogeographic patterns, with functional turnover being pronounced in the Palaeotropical rainforest. These findings highlight the key role of spatial processes in shaping WTH metacommunities and emphasise the need for conservation strategies that maintain habitat connectivity and old-growth forests.

Adaptation to abiotic stresses generally relies on traits that are not independent from those affecting species interactions. Still, the impact of such evolutionary processes on coexistence remains elusive. Here, we studied two spider mite species evolving separately on tomato plants that hyper-accumulated cadmium, a stressful environment for herbivores, or on plants without cadmium. Through experimental evolution and structural stability theory, we found that both species coexist in the cadmium environment, but the evolution of a single species in cadmium leads to exclusion. However, when both species evolve in cadmium they can coexist. This shift occurred due to a simultaneous increase in intra and a decrease in interspecific competition in that environment. These predictions were further confirmed with complementary experiments of population dynamics. Therefore, population shifts to novel environments, even in the absence of interspecific competitors, may have unforeseen evolutionary consequences for community composition and the maintenance of species diversity.

Understanding diversity patterns in complex communities, such as microbial consortia, requires a mechanistic framework appropriate for many species. Negative density dependence is often utilised in complex ecosystem models, typically as a density-dependent mortality term for a population, but its full impact on community structure remains unclear. Here we use mechanistic population models of resource consumption to examine the effects of negative density dependence and develop a tractable framework for understanding diversity patterns in complex systems. To provide mechanistic grounding, we quantify how density-dependent mortality expands coexistence zones along resource gradients in simple communities using graphical analysis. We then derive an analytical formula relating species abundances and coexistence patterns to trait differences among subsets (guilds) of complex communities, in which many species share a resource or predator. Finally, we explain how distinct relationships between productivity and diversity emerge from the resulting mechanistic framework, providing insights into previously unreconciled observed patterns.

Soil microorganisms mediate carbon and nutrient fluxes in soils, and—as all organisms—are subject to eco-evolutionary dynamics. Adaptation of soil microbial functionality to environmental conditions across space and time has consequences for biogeochemical fluxes that are often not explicitly considered in models describing soil organic matter (SOM) dynamics. Eco-evolutionary optimization (EEO) tries to anticipate the outcome of eco-evolutionary dynamics, and can inform on how microbial functional traits might adapt to environmental conditions based on the maximisation of different proxies of microbial fitness. While different approaches employ different fitness proxies, they all aim to increase realism and generality by grounding SOM models in eco-evolutionary theory and introducing constraints on model parametrization. Despite this potential, challenges for widely applying EEO approaches to advance SOM models persist and open questions remain, primarily concerning implicit assumptions, convergence of predictions, and empirical validation of the different EEO approaches. In this Synthesis, we review EEO approaches that have been applied to SOM models and provide an instructive primer to EEO approaches. We then propose a general categorization, aiming to make their underlying assumptions explicit and give an outlook for future research directions.