Unveiling the drivers of persistence and stability in complex networks of species interactions is a grand challenge in ecological research. Recent findings have revealed how the balance between different interaction types and network structure play a key role in maintaining stability. In mutualistic networks, it has been shown that effective competition -the net competition amongst all species once competitive and mutualistic effects are accounted for- should not exceed a given threshold value (critical competition) for the community to persist.
The shape of ecological communities is a product of ecological and evolutionary processes acting together to create the complex picture of biodiversity that we observe in Nature. Understanding how these eco-evolutionary dynamics have produced feasible community compositions and network structures will reveal the mechanisms giving rise to complex communities that so far remain elusive. In this work we tackle this challenge using a dynamical model of mutualistic network assembly, incorporating interaction-driven population dynamics and the evolution of interactions, to investigate how the interplay between ecology and evolution shapes the relationship between competitive and mutualistic interactions in complex mutualistic networks. Using this model we answer the question of how eco-evolutionary dynamics facilitate biodiversity persistence through a balance of different ecological interactions.
Results/Conclusions
Our results show that evolution enhances biodiversity when competition is weak or when environmental perturbations are strong. We found a changing relationship between mutualistic evolution through selection and interspecific competition along gradients of environmental perturbation. Biodiversity is always enhanced when direct competition is weak. However, the extent of this advantage in evolving communities, when compared to scenarios without selection, increases from low to intermediate levels of environmental perturbation, only to even out in scenarios of large environmental perturbations, when biodiversity is overall very low.
Additionally, our results suggest that the evolutionary mechanism for this enhanced biodiversity is an increased critical competition to avoid collapse. In situations when competitive interactions are kept constant, evolution will favour system re-organisation in ways that increase the competition threshold that limits system’s persistence: critical competition. This effect is accentuated when effective competition is larger than the baseline critical competition threshold.
Our framework provides the first steps towards an eco-evolutionary theory of ecological networks considering mutualistic and competitive interactions. Our results can have implications for biodiversity conservation as the effective competition between species in ecosystems can be strongly affected by different aspects of global change through the differential strengthening of different interaction types.
