Specific arrangements of species dominance can be more influential than evenness in maintaining ecosystem process and function.

Daniel Wohlgemuth,Martin Solan,Jasmin A Godbold

doi:10.1038/srep39325

Daniel Wohlgemuth, Martin Solan + Show 1 more

Open Access

https://doi.org/10.1038/srep39325

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Abstract

The ecological consequences of species loss are widely studied, but represent an end point of environmental forcing that is not always realised. Changes in species evenness and the rank order of dominant species are more widespread responses to directional forcing. However, despite the repercussions for ecosystem functioning such changes have received little attention. Here, we experimentally assess how the rearrangement of species dominance structure within specific levels of evenness, rather than changes in species richness and composition, affect invertebrate particle reworking and burrow ventilation behaviour - important moderators of microbial-mediated remineralisation processes in benthic environments - and associated levels of sediment nutrient release. We find that the most dominant species exert a disproportionate influence on functioning at low levels of evenness, but that changes in biomass distribution and a change in emphasis in species-environmental interactions become more important in governing system functionality as evenness increases. Our study highlights the need to consider the functional significance of alterations to community attributes, rather than to solely focus on the attainment of particular levels of diversity when safeguarding biodiversity and ecosystems that provide essential services to society.

Highlights

Alterations to biodiversity influence the functioning of ecosystems and, by extension, the services that benefit human society, as evidenced by a plethora of experiments that have altered the number of genes, species or functional groups within a community and observed associated changes in ecosystem functioning and services[1]
Whilst theory predicts that increases in evenness will enhance synergistic interspecific interactions that intensify species contributions to ecosystem functioning[12], empirical studies that have examined the effects of changes in evenness on ecosystem properties report mixed results
Important aspects of species interactions[14]. These can be antagonistic or synergistic depending on the identity and relative abundances of the interacting species[23] and can lead to negative or positive consequences for ecosystem functioning[12,15,24]. It is the interplay between species dominance and the relative distribution of traits within a community that can be important in moderating ecosystem properties[25,26], because multiple permutations of dominance structure are possible, and are likely to affect the strength and direction of species interactions, within each level of evenness

Summary

Introduction

Alterations to biodiversity influence the functioning of ecosystems and, by extension, the services that benefit human society, as evidenced by a plethora of experiments that have altered the number of genes, species or functional groups within a community and observed associated changes in ecosystem functioning and services[1]. The effects of natural or human-induced factors on biological communities are not solely limited to the adjustment of species richness, they affect other important aspects of biodiversity, in particular species evenness[2,3,4], the identity and rank order of dominant species[5,6], and the spatial arrangement of individuals within a community[7,8] Changes in such community attributes tend to depend on biotic and/or abiotic context across scales, from local habitat conditions[7] to climatic forcing[2], occur over extended timescales and are often a prelude to local species extinction[9]. If our expectations are met, it raises the possibility that the use of simple diversity metrics to represent complex communities may form an insufficient vehicle for determining the functional integrity of an ecosystem[28,29,30]

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