The multiscale feedback theory of biodiversity

Distinguishing local and regional processes that underpin biodiversity is complex because they are inherently correlated: positive ecosystem engineers tend to be members of low-diversity species pools; plants exhibiting small-scale negative feedback tend to be members of diverse pools. Observed communities represent a gradient of transition between diverse, negative feedback-driven and species-poor, positive feedback-driven systems. Over biogeographical timescales, poor systems tend to diversify, while migration or emergence of positive ecosystem engineers produces low-diversity systems. The distinction between diverse, small-scale negative feedback-driven and poor, positive ecosystem engineer-driven communities corresponds to opposing historical perceptions of how communities are organised: the former to Gleason’s individualistic communities, the latter to Clements’s holistic communities. Plants and their environments engage in feedback loops that not only affect individuals, but also scale up to the ecosystem level. Community-level negative feedback facilitates local diversity, while the ability of plants to engineer ecosystem-wide conditions for their own benefit enhances local dominance. Here, we suggest that local and regional processes influencing diversity are inherently correlated: community-level negative feedback predominates among large species pools formed under historically common conditions; ecosystem-level positive feedback is most apparent in historically restricted habitats. Given enough time and space, evolutionary processes should lead to transitions between systems dominated by positive and negative feedbacks: species-poor systems should become richer due to diversification of dominants and adaptation of subordinates; however, new monodominants may emerge due to migration or new adaptations. Plants and their environments engage in feedback loops that not only affect individuals, but also scale up to the ecosystem level. Community-level negative feedback facilitates local diversity, while the ability of plants to engineer ecosystem-wide conditions for their own benefit enhances local dominance. Here, we suggest that local and regional processes influencing diversity are inherently correlated: community-level negative feedback predominates among large species pools formed under historically common conditions; ecosystem-level positive feedback is most apparent in historically restricted habitats. Given enough time and space, evolutionary processes should lead to transitions between systems dominated by positive and negative feedbacks: species-poor systems should become richer due to diversification of dominants and adaptation of subordinates; however, new monodominants may emerge due to migration or new adaptations. mechanisms that tend to minimise average fitness differences between species. negative density dependence in a local population. As the density of conspecifics increases, the burden of negative impacts, either intraspecific resource competition, negative biotic interactions due to the accumulation of antagonistic organisms (pathogens, parasites, herbivores, seed predators) or adverse changes to the abiotic conditions (e.g., shading), also increases. species that can significantly modify biotic and/or abiotic environments for their benefit. positive density dependence: as the density of conspecifics increases, the net benefit of positive impacts (mutualistic biotic interactions or beneficial changes to the abiotic conditions) also increases. sets of species that occur in particular areas and that could inhabit a site due to suitable ecological conditions. For different types of species pool, see [108.Zobel M. The species pool concept as a framework for studying patterns of plant diversity.J. Veg. Sci. 2016; 27: 8-18Crossref Scopus (127) Google Scholar]. mechanisms that tend to increase negative intraspecific interactions relative to negative interspecific interactions.