Abstract
In natural ecosystems, hundreds of species typically share the same environment and are connected by a dense network of interactions such as predation or competition for resources. Much is known about how fixed ecological niches can determine species abundances in such systems, but far less attention has been paid to patterns of abundances in randomly varying environments. Here, we study this question in a simple model of competition between many species in a patchy ecosystem with randomly fluctuating environmental conditions. Paradoxically, we find that introducing noise can actually induce ordered patterns of abundance-fluctuations, leading to a distinct periodic variation in the correlations between species as a function of the phenotypic distance between them; here, difference in growth rate. This is further accompanied by the formation of discrete, dynamic clusters of abundant species along this otherwise continuous phenotypic axis. These ordered patterns depend on the collective behavior of many species; they disappear when only individual or pairs of species are considered in isolation. We show that they arise from a balance between the tendency of shared environmental noise to synchronize species abundances and the tendency for competition among species to make them fluctuate out of step. Our results demonstrate that in highly interconnected ecosystems, noise can act as an ordering force, dynamically generating ecological patterns even in environments lacking explicit niches.
Highlights
Species abundances and their variation over time are quantities of fundamental importance in any ecosystem: understanding the forces that shape them is a key part of central problems in ecology, ranging from conceptual questions about the role of neutral processes [1,2] to practical issues in biodiversity conservation [3]
We show that environmental noise can lead to robust, dynamic patterns in phenotype space
The specific formulation was inspired by the rich microbial communities found in soil, but its basic features – patchiness, repeated environmental disturbances, and the presence of a range of different phenotypic strategies – are shared by many ecosystems
Summary
Species abundances and their variation over time are quantities of fundamental importance in any ecosystem: understanding the forces that shape them is a key part of central problems in ecology, ranging from conceptual questions about the role of neutral processes [1,2] to practical issues in biodiversity conservation [3]. Significant progress has been made towards quantifying the total impact of each of these factors [21,22,23], it remains unknown how the tension between them influences the dynamics in natural ecosystems In such systems, many phenotypically distinct species are embedded in a tangled web of direct and indirect interactions that make it hard to predict the effect of even simple disturbances [24,25,26], and non-trivial collective effects could play a significant role. Such phenotypic patterns could be ubiquitous but have received relatively little attention [30]
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