Differential Responses of Food Web Properties to Opposite Assembly Rules and Species Richness

Yulun Guo,Min Zhang,García Molinos Jorge,Peiyu Zhang,Jun Xu,Tao Wang,Huan Zhang

doi:10.3390/w12102828

Abstract

Trophic niches condition the energetic performance of species within food webs providing a vital link between food web assembly, species diversity, and functioning of ecosystems. Our understanding of this important link is, however, limited by the lack of empirical tools that can be easily applied to compare entire food webs at regional scales. By comparison, with different a priori synthetic models defined according to specific assembly rules (i.e., purely random, limiting similarity, and niche filtering), we demonstrate that a set of food web properties (trophic richness, evenness, and divergence) are controlled by ecological processes. We further demonstrate that although both limiting similarity and niche filtering are statistically significant assembly processes shaping our studied lake food webs, their relative importance is richness-dependent, and contextual to the specific food web property under consideration. Our results have both important theoretical and practical implications. Theoretically, the observed richness-dependent variation on food web properties contradicts the common criticism on food web theory that food web properties are roughly scale-invariant. Practically, these properties can help avoiding spurious conclusions, while providing useful information for multiple food web niche spaces supporting the ecosystem functioning.

Highlights

Our planet is experiencing unprecedented rates of human-induced loss of species and population declines across all major ecosystems with anticipated effects on ecosystem functioning and human well-being: the “anthropocene defaunation” [1]
A total of 192 species were recorded from the 165 assemblages with a richness of 40 ± 28 and a range of 3–112 species spanning a wide range of benthivory and trophic positions (Figure 2)
Trophic richness and evenness were relatively insensitive to the loss of species at high species richness until a certain threshold was reached, from which further reductions in species numbers produced a rapid decline of both properties

Summary

Introduction

Our planet is experiencing unprecedented rates of human-induced loss of species and population declines across all major ecosystems with anticipated effects on ecosystem functioning and human well-being: the “anthropocene defaunation” [1]. The impacts of species loss are restricted to target populations, and have wider implications by altering predator–prey ratios within food webs, which can lead to community-wide alterations via cascading community effects [2,3]. Under this scenario, studies of food web assembly and dynamics are of great importance for better understanding the ecology of stressed ecosystems and their potential vulnerability to collapse [4]. The niche filtering hypothesis assumes that coexisting species are more similar to one another than would be expected by chance because environmental conditions (i.e., abiotic properties of the habitat) act as a filter allowing only a narrow spectrum of species to survive in their niche space [20]

Methods

Results

Discussion

Conclusion