Syrphidae of the Southern Appalachians: Diversity, Distribution, and Foraging Behavior

Coleman, Padraig

ABSTRACT: Flies of the family Syrphidae, commonly known as syrphid or hoverflies, are an ecologically underappreciated taxon of insects. They are a widespread and diverse group within Diptera consisting of over 6000 species worldwide, and are thought to be second only to native bees as pollinators of native plants. The larval stages of many species are predatory towards common plant pests such as aphids, making them promising biological control agents in both natural and agricultural settings. Despite the dual ecosystem services offered by their holometabolous lifestyle, studies focusing exclusively on syrphids are relatively limited, particularly throughout the Southern Appalachians. In response to global bee declines, there has been increased interest in the contributions of non-bee pollinators and syrphid flies have emerged as one of the most prominent of these taxa. My study seeks to describe the diversity and distribution of syrphid flies along the Blue Ridge Parkway, as well as explore aspects of their foraging behavior relevant to their efficacy as pollinators. Syrphids were collected through passive trapping (2018, 2019) and active netting (2021-2023) at over 100 sites alongside the Blue Ridge Parkway in North Carolina and Virginia. These surveys revealed an overwhelming 81 species that had previously gone undocumented along the parkway. Occurrence data from these surveys were used to create habitat suitability maps for ten common species throughout the park. Measures of temperature and vapor deficit were found to be one of the most influential bioclimatic variables across species, suggesting that factors relating to aridity strongly impact the distribution of Syrphidae. I also documented the associations of syrphids with local Southern Appalachian Flora by creating bipartite models to represent community networks, and quantified visitation patterns during transitions among encountered flowers. Hoverfly species were found to feed on a wide range of flower types, but individuals remained constant to preferred species during foraging bouts. These results support the idea that hoverflies are a prominent group of pollinators that could provide valuable insurance for pollination services in the face of bee declines, and provides a valuable baseline for future studies of an essential yet often forgotten pollinator group.