Abstract
Pollination is a key ecosystem service for agriculture and wider ecosystem function. However, most pollination studies focus on Hymenoptera, with hoverflies (Syrphidae) frequently treated as a single functional group. We tested this assumption by investigating pollen carried by eleven species of hoverfly in five genera, Cheilosia, Eristalis, Rhingia, Sericomyia and Volucella, using DNA metabarcoding. Hoverflies carried pollen from 59 plant taxa, suggesting they visit a wider number of plant species than previously appreciated. Most pollen recorded came from plant taxa frequently found at our study sites, predominantly Apiaceae, Cardueae, Calluna vulgaris, Rubus fruticosus agg., and Succisa pratensis, with hoverflies transporting pollen from 40% of entomophilous plant species present. Overall pollen transport network structures were generalised, similar to other pollination networks elsewhere. All hoverfly species were also generalised with few exclusive plant/hoverfly interactions. However, using the Jaccard Index, we found significant differences in the relative composition of pollen loads between hoverfly genera, except for Volucella, demonstrating some degree of functional complementarity. Eristalis and Sericomyia species had significant differences in relative pollen load composition compared to congeners. Our results demonstrate the range of pollens transported by hoverflies and the potential pollination function undertaken within this ecologically and morphologically diverse guild.
Highlights
Pollination is a key ecosystem service which sustains significant food production[1,2]
Mouthpart length in hoverflies has been shown to have some influence on flower selection[22,23], which could in turn affect pollination network structure[24]
Using the Jaccard Index, we investigated the similarity in pollen load composition between the five genera, and between species in two genera, Eristalis and Sericomyia, where more than one species was available
Summary
Pollination is a key ecosystem service which sustains significant food production[1,2]. Understanding interactions between wild pollinators and plants is critical, because pollination network structure has implications for the stability of pollination as an ecosystem service in the face of environmental change[5,6,7]. The plant species in these networks are predominantly ecological and functional generalists, with flowers that are accessible to a range of potential pollinators[10,11]. Such generalised networks can be more robust to species extinctions, because plants are able to exchange pollinator species if pollinator populations fluctuate[12]. The visual identification of pollen can be challenging, even for experienced observers, given the similarity in pollen morphology within some plant families[31]
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