Large herbivores facilitate an insect herbivore by modifying plant community composition in a temperate grassland

Xiaofei Li, Shengnan Wang, Chelse Prather, Ho Yi Wan, Hui Zhu, Petri Nummi, Moshe Inbar, Qiang Gao, Deli Wang, Zhiwei Zhong

Research output: Contribution to journalArticlepeer-review

Abstract

Large herbivores often co-occur and share plant resources with herbivorous insects in grassland ecosystems; yet, how they interact with each other remains poorly understood. We conducted a series of field experiments to investigate whether and how large domestic herbivores (sheep; Ovis aries) may affect the abundance of a common herbivorous insect (aphid; Hyalopterus pruni) in a temperate grassland of northeast China. Our exclosure experiment showed that 3 years (2010–2012) of sheep grazing had led to 86% higher aphid abundance compared with ungrazed sites. Mechanistically, this facilitative effect was driven by grazing altering the plant community, rather than by changes in food availability and predator abundance for aphids. Sheep significantly altered plant community by reducing the abundance of unpalatable forbs for the aphids. Our small-scale forb removal experiment revealed an “associational plant defense” by forbs which protect the grass Phragmites australis from being attacked by the aphids. However, selective grazing on forbs by sheep indirectly disrupted such associational plant defense, making P. australis more susceptible to aphids, consequentially increasing the density of aphids. These findings provide a novel mechanistic explanation for the effects of large herbivores on herbivorous insects by linking selective grazing to plant community composition and the responses of insect populations in grassland ecosystems.

Original languageEnglish
Pages (from-to)16314-16326
Number of pages13
JournalEcology and Evolution
Volume11
Issue number22
DOIs
StatePublished - Nov 2021

Bibliographical note

Funding Information:
We thank field assistance from Yubo Gao and Hongan Li and Judith Bronstein and Kailen Mooney for useful comments on early drafts of this article. This project was supported by the National Natural Science Foundation of China (No. 32061143027, 32001384, 31770520), the Joint NSFC‐ISF (China‐Israel) research grant (3429/20), the Fundamental Research Funds for the Central Universities (2412020FZ019), the State Key Laboratory of Grassland Agro‐ecosystem of Lan Zhou University (SKLGAE201904), and the Natural Science Foundation of Jilin Province Science and Technology Department (20200201003JC).

Funding Information:
We thank field assistance from Yubo Gao and Hongan Li and Judith Bronstein and Kailen Mooney for useful comments on early drafts of this article. This project was supported by the National Natural Science Foundation of China (No. 32061143027, 32001384, 31770520), the Joint NSFC-ISF (China-Israel) research grant (3429/20), the Fundamental Research Funds for the Central Universities (2412020FZ019), the State Key Laboratory of Grassland Agro-ecosystem of Lan Zhou University (SKLGAE201904), and the Natural Science Foundation of Jilin Province Science and Technology Department (20200201003JC).

Publisher Copyright:
© 2021 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.

Keywords

  • associational defense
  • community
  • ecosystem engineering
  • facilitation
  • herbivore–herbivore interactions
  • herbivory
  • neighboring plants

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Ecology
  • Nature and Landscape Conservation

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