Generalisation and specialisation in hoverfly (Syrphidae) grassland pollen transport networks revealed by DNA metabarcoding

• Type of Material: Article
• Authors: Andrew Lucas, Swansea University; Owen Bodger, Swansea University; Berry J Brosi, Emory University; Col R. Ford, National Botanic Garden of Wales; Dan W. Forman, Swansea University; Carolyn Greig, Swansea University; Matthew Hegarty, Aberystwyth University; Penelope J. Neyland, Swansea University; Natasha de Vere, National Botanic Garden of Wales; Nathan Sanders, University of Copenhagen
• Language: English
• Date: 2018-07
• Publisher: Wiley
• Publication Version: Final Published Version
• Copyright Statement: © 2018 The Authors. Journal of Animal Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1111/1365-2656.12828
• Title of Journal or Parent Work: Journal of Animal Ecology
• ISSN: 0021-8790
• Volume: 87
• Issue: 4
• Start Page: 1008
• End Page: 1021
• Grant/Funding Information: The National Botanic Garden of Wales receives support from the Welsh Government Rural Communities—Rural Development Programme 2014–2020, which is funded by the European Agricultural Fund for Rural Development and the Welsh Government.; The Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, receives strategic funding from BBSRC.
• Keywords: grassland; DNA metabarcoding; specialisation; generalisation; pollination; pollination networks; hoverfly
• Research Categories: Biology, Plant Physiology

Abstract

1. Pollination by insects is a key ecosystem service and important to wider ecosystem function. Most species‐level pollination networks studied have a generalised structure, with plants having several potential pollinators, and pollinators in turn visiting a number of different plant species. This is in apparent contrast to a plant's need for efficient conspecific pollen transfer. 2. The aim of this study was to investigate the structure of pollen transport networks at three levels of biological hierarchy: community, species and individual. We did this using hoverflies in the genus Eristalis, a key group of non‐Hymenopteran pollinators. 3. We constructed pollen transport networks using DNA metabarcoding to identify pollen. We captured hoverflies in conservation grasslands in west Wales, UK, removed external pollen loads, sequenced the pollen DNA on the Illumina MiSeq platform using the standard plant barcode rbcL, and matched sequences using a pre‐existing plant DNA barcode reference library. 4. We found that Eristalis hoverflies transport pollen from 65 plant taxa, more than previously appreciated. Networks were generalised at the site and species level, suggesting some degree of functional redundancy, and were more generalised in late summer compared to early summer. In contrast, pollen transport at the individual level showed some degree of specialisation. Hoverflies defined as “single‐plant visitors” varied from 40% of those captured in early summer to 24% in late summer. Individual hoverflies became more generalised in late summer, possibly in response to an increase in floral resources. Rubus fruticosus agg. and Succisa pratensis were key plant species for hoverflies at our sites. 5. Our results contribute to resolving the apparent paradox of how generalised pollinator networks can provide efficient pollination to plant species. Generalised hoverfly pollen transport networks may result from a varied range of short‐term specialised feeding bouts by individual insects. The generalisation and functional redundancy of Eristalis pollen transport networks may increase the stability of the pollination service they deliver.