Expansion, Exploitation and Extinction: Niche Construction in Ephemeral Landscapes

Miles T Wetherington,Juan E Keymer

doi:10.1038/s41598-020-66888-9

Abstract

We aim to understand general consequences of niche construction on metapopulation dynamics in ephemeral landscapes. To this effect, a contact process-like stochastic spatial model is introduced where local populations colonize and go extinct on a dynamic landscape of habitable and destroyed patches. In contrast to previous models, where the extinction threshold is a consequence of available niche rendered by global rates of patch destruction/renewal, here we investigate how the metapopulation persists when they are the sole generators of their own niche. Niche construction is full-filled by localized populations through the transformation of destroyed patches in their neighborhood to viable habitat for future colonization. With this theoretical framework we are able to address the dual nature of niche construction by investigating the ephemerality of the landscape (destruction rate) and the continuum of population level strategies, where construction comes at a cost to colonization. Using mean field theory and Monte Carlo simulations of the model, we are able to quantify optimal population level strategies in a wide range of ephemeral landscapes. Interestingly, we observe qualitative differences at the extinction threshold between analytic and numeric results. Investigating this discrepancy further, we find that increasing niche construction neighborhood in the spatial model leads to two interrelated effects i) an increased rate in range expansion ii) a loss in resiliency and return of the discontinuous transition at the extinction threshold. Furthermore, in the discontinuous regime of the model, spatial clustering prior to a critical transition disappears. This is a significant finding as spatial clustering has been considered to be an early warning signal before ecosystems reach their ‘tipping point’. In addition to maintaining stability, we find local niche construction strategies have an advantage when in scramble competition with an exploiter strategy because of their ability to monopolize the constructed niche due to spatial adjacency. As the niche construction neighborhood expands this advantage disappears and the exploiter strategy out-competes the niche constructor. In some cases the exploiter pushes the niche constructor to extinction, thus a tragedy of the commons ensues leading to ‘ecological suicide’ and a collapse of the niche.

Highlights

Understanding the co-regulatory feedback between living systems and their environment is a primary goal driving ecological research[1,2,3]
Such microbial consortia act as their own ecological units, often coexisting in harmony[13] and expanding beyond the niche of any one strategy. Such niche construction has a tighter feedback to the ecological unitpopulation in question and can play an important role in influencing their evolutionary trajectory even playing a vital role in biogeochemical cycles[14]
Effect of niche construction neighborhood on range expansion and resiliency. In light of these striking discrepancies between spatial model and mean field approximation (MFA) prediction, we investigated the effect of construction range (r) on range expansion by the metapopulation starting from a single occupied site

Summary

Introduction

Understanding the co-regulatory feedback between living systems and their environment is a primary goal driving ecological research[1,2,3]. The microbial world is typified by such feedback processes; for example, the exchange of metabolic byproducts plays an important role in creating and maintaining interdependent or ‘syntrophic’ relationships where two or more microbial groups live symbiotically via nutrient cross-feeding[11] or the transaction of other resources[12] Such microbial consortia act as their own ecological units, often coexisting in harmony[13] and expanding beyond the niche of any one strategy. Such niche construction has a tighter feedback to the ecological unitpopulation in question and can play an important role in influencing their evolutionary trajectory even playing a vital role in biogeochemical cycles[14] In this way niche construction is a life history trait which has the potential to expand or maintain the ecological a populations niche, including the trans-generational inheritance of improved local conditions (ecological inheritance). A similar mechanism has been well documented with Pseudomonas aeruginosa which, in iron-limited conditions, will begin to excrete an ‘iron scavenging’ extracellular compound (siderophore) to bind and transport iron across the cell membrane[23]

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Discussion

Conclusion