Stability lies in flowers: Plant diversification mediating shifts in arthropod food webs.

Marcelo Mendes Haro,Andrew Wilby,Luís Cláudio Paterno Silveira,Raul Narciso Carvalho Guedes

doi:10.1371/journal.pone.0193045

Abstract

Arthropod community composition in agricultural landscapes is dependent on habitat characteristics, such as plant composition, landscape homogeneity and the presence of key resources, which are usually absent in monocultures. Manipulating agroecosystems through the insertion of in-field floral resources is a useful technique to reduce the deleterious effects of habitat simplification. Food web analysis can clarify how the community reacts to the presence of floral resources which favour ecosystem services such as biological control of pest species. Here, we reported quantitative and qualitative alterations in arthropod food web complexity due to the presence of floral resources from the Mexican marigold (Tagetes erecta L.) in a field scale lettuce community network. The presence of marigold flowers in the field successfully increased richness, body size, and the numerical and biomass abundance of natural enemies in the lettuce arthropod community, which affected the number of links, vulnerability, generality, omnivory rate and food chain length in the community, which are key factors for the stability of relationships between species. Our results reinforce the notion that diversification through insertion of floral resources may assist in preventing pest outbreaks in agroecosystems. This community approach to arthropod interactions in agricultural landscapes can be used in the future to predict the effect of different management practices in the food web to contribute with a more sustainable management of arthropod pest species.

Highlights

In agricultural landscapes richness and abundance of arthropods are dependent on local habitat characteristics, which are determined by the different strategies used in the management of the agroecosystem [1, 2]
The difference in richness was significant, the arthropods collected were distributed across the 5 trophic levels with at least one representative of each level in each the three cultivations (Figs 2, 3 and 4)
Planting of T. erecta within the crop modified the arthropod community associated with lettuce plants, changing the structure, biomass distribution, assumed species interactions and consumer/prey properties in the arthropod food webs

Summary

Introduction

In agricultural landscapes richness and abundance of arthropods are dependent on local habitat characteristics, which are determined by the different strategies used in the management of the agroecosystem [1, 2]. Several pieces of evidence indicate that arthropod communities are directly affected by field simplification and loss of non-crop habitats in monocultures, causing distortion in species relative abundance, removing natural enemies from the crop may increase the likelihood for outbreaks [3,4,5]. Enhancing arthropod food webs design, data collection and analysis, decision to publish, or preparation of the manuscript

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Conclusion