Grazer responses to variable macroalgal resource conditions facilitate habitat structuring.

Gavin M Rishworth,Matthew S Bird,Noémie Pelletier,Renzo Perissinotto

doi:10.1098/rsos.171428

Gavin M Rishworth, Matthew S Bird + Show 2 more

Open Access

https://doi.org/10.1098/rsos.171428

Copy DOI

Abstract

Consumer responses to altered resource conditions can vary depending on dietary preference, resource characteristics and secondary resource features such as shelter. These can have cascading effects, especially if the consumed resource impacts on overall ecological functioning. In this study, we assessed the dietary composition of grazer communities following seasonal changes in the characteristics of their staple food-source (macroalgae). This was conducted in the living stromatolite pools growing along the coast of South Africa. Stable isotope mixing models suggested that following macroalgal bleaching in summer, metazoan consumers shifted their diet from predominantly macroalgae to a generalist composition. This has important implications for the integrity of the stromatolite matrix and its layered deposition. Where previously in winter stromatolite microalgae comprised a minor component of metazoan consumer diets, in summer, following a change in the resource conditions of macroalgae, microalgae featured more prominently in grazer diets. This seasonal grazing pressure on stromatolite-related resources probably promotes the pattern of annual layering observed in the stromatolite accretion. It also demonstrates a mechanism whereby grazer dietary shifts following a change in their preferred food resource can affect the ecosystem structure of their environment, specifically the stromatolite layering process which responds to microalgal growth or grazing conditions.

Highlights

Optimal foraging theory dictates that a consumer organism will maximize its current resource uptake up to the point at which2018 The Authors
Stable isotope mixing models suggested that following macroalgal bleaching in summer, metazoan consumers shifted their diet from predominantly macroalgae to a generalist composition
The decision to move 2 to a new foraging location or resource is confounded by several factors, including predator presence [4], secondary food resource attributes such as shelter [5] and the interaction between conspecifics or competitors [6]

Summary

Introduction

Optimal foraging theory dictates that a consumer organism will maximize its current resource uptake up to the point at which2018 The Authors. The decision to move 2 to a new foraging location or resource is confounded by several factors, including predator presence [4], secondary food resource attributes such as shelter [5] and the interaction between conspecifics or competitors [6]. Changes in resource availability or quality can influence the foraging behaviour of consumers. Competition for shared resources drives foraging decisions or behaviours [10], with increased intraspecific interactions promoting dietary diversification and individual-level specialization [11]. These are important drivers of eco-evolutionary population change, whereby resource-driven competition selects for divergent foraging traits and phenotypic attributes [12]

Methods

Results

Conclusion