Coexistence Mechanisms in Ecological Communities

Coexistence in ecological communities arises from a balance between niche differentiation, which reduces direct competition by partitioning resources or habitats, and mechanisms that equalise fitness differences among species, thereby preventing dominant taxa from excluding others. Stabilising processes such as negative frequency dependence, spatial heterogeneity and temporal variability create conditions that favour rare species, while equalising processes diminish inherent disparities in growth rates or survival. Higher-order interactions, in which the presence of additional species modulates pairwise relationships, and priority effects, where the order of arrival influences long-term composition, further shape assembly outcomes. Overlaying these deterministic mechanisms, stochastic influences—both environmental and demographic—introduce variability that can reinforce or undermine coexistence. Together, these factors govern patterns of diversity, community stability and resilience across scales, from microbial consortia to complex terrestrial and marine ecosystems, with implications for biodiversity conservation, ecosystem management and the prediction of community responses to global change.

Research from Nature Portfolio

Recent empirical work has tested unified theories of niche versus dispersal assembly, demonstrating in tropical intertidal communities that high immigration rates can overfill limited niche space, placing systems in dispersal-assembled regimes with richness exceeding classical niche limits. Range-edge field experiments in mountainous plant assemblages have shown that competitive interactions define both warm and cool elevational boundaries, driven by shifts in niche differentiation and relative fitness along gradients. Theoretical simulations of complex networks reveal that higher-order interactions invert traditional diversity–stability trade-offs: four-way interactions decrease sensitivity to species addition and removal, thereby establishing both lower and upper diversity bounds and highlighting the role of multi-species interaction structures in maintaining ecosystem diversity.

Coexistence Mechanisms in Ecological Communities publication trend

The graph below shows the total number of articles in coexistence mechanisms in ecological communities across all publications each year (not limited to Nature Index journals).

Technical terms

Niche differentiation: Process by which species exploit distinct resources or conditions to reduce direct competition.

Fitness differences: Variations in intrinsic growth rates or survival probabilities that influence competitive outcomes.

Stabilising mechanisms: Factors that generate negative frequency dependence, favouring the persistence of less abundant species.

Equalising mechanisms: Processes that minimise average fitness disparities among species to prevent exclusion.

High-order interactions: Multi-species effects whereby additional community members alter the strength or outcome of pairwise interactions.

Stochasticity: Random demographic or environmental variation that influences species abundances and assembly trajectories.

References

1. Unveiling the transition from niche to dispersal assembly in ecology. Nature (2023).
2. Competition contributes to both warm and cool range edges. Nature Communications (2022).
3. High-order species interactions shape ecosystem diversity. Nature Communications (2016).
4. Higher order interactions and species coexistence. Theoretical Ecology (2020).
5. Diversity and coexistence are influenced by time‐dependent species interactions in a predator–prey system. Ecology Letters (2020).
6. Integrating the underlying structure of stochasticity into community ecology. Ecology (2019).