Abstract
Pollinator declines, changes in land use and climate-induced shifts in phenology have the potential to seriously affect ecosystem function and food security by disrupting pollination services provided by insects. Much of the current research focuses on bees, or groups other insects together as ‘non-bee pollinators’, obscuring the relative contribution of this diverse group of organisms. Prominent among the ‘non-bee pollinators’ are the hoverflies, known to visit at least 72% of global food crops, which we estimate to be worth around US$300 billion per year, together with over 70% of animal pollinated wildflowers. In addition, hoverflies provide ecosystem functions not seen in bees, such as crop protection from pests, recycling of organic matter and long-distance pollen transfer. Migratory species, in particular, can be hugely abundant and unlike many insect pollinators, do not yet appear to be in serious decline. In this review, we contrast the roles of hoverflies and bees as pollinators, discuss the need for research and monitoring of different pollinator responses to anthropogenic change and examine emerging research into large populations of migratory hoverflies, the threats they face and how they might be used to improve sustainable agriculture.
Highlights
Animal-mediated pollination is a critical process for supporting both natural ecosystems and human food security by facilitating reproduction of much of the world’s plant life [1]
Of those plants selected as crops by humans over the last 13 000 years, around 76% are dependent on animal pollination [2,3]
The family is traditionally organized into three subfamilies, two of which are considered important in terms of pollination, the Syrphinae and the Eristalinae, made up of around 1800 and 3800 species, respectively [11]
Summary
Animal-mediated pollination is a critical process for supporting both natural ecosystems and human food security by facilitating reproduction of much of the world’s plant life [1]. Include various forms of zoophagy, phytophagy, coprophagy and saprophagy (see [11,15] for a full account) In many cases, these stages provide important additional ecosystem services, for example, some species in the subfamily Syrphinae provide biocontrol of crop pests, consuming vast numbers of aphids during their development [11,15,16,17,18,19] while filter-feeding saprophagous larvae are very common among the Eristalinae and include ‘rat-tailed maggot’ forms adapted to aquatic environments and important for the recycling of waste [11,20]. Adults typically feed on nectar and pollen and their morphologies range from large, hirsute bumblebee mimics, to miniscule hairless species with mimicry of bees and wasps widespread [21,22] Given their important role in pollination and provision of other ecosystems functions, hoverflies are gaining particular interest as beneficial species and alternative managed pollinators. We provide a synthesis of hoverflies as pollinators, highlight the impact of anthropogenic change on their populations and discuss key avenues for future research
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