Species diversity in bee flies and hover flies (Diptera: Bombyliidae and Syrphidae) in the horticultural environments of the Blue Mountains, Australia.
Flies (Diptera) are one of the most important groups of insect pollinators. Families Bombyliidae (bee flies) and Syrphidae (hover flies) are globally distributed with aproximately 5000 and 6200 described species, respectively. Many studies have attempted to quantify Syrphidae diversity in natural and agricultural environments, due to their perceived value as pollinators, decomposers of organic waste and agents of pest control. However, to date, there have been only two studies of Syrphidae communities in Australia, both of which focused on arable crops. Meanwhile, there have been very few studies of Bombyliidae diversity and none in Australia, despite the fact that bombyliid diversity can be high, far exceeding that of Syrphidae in some ecosystems. We aimed to learn more about Australia's anthophilous Diptera and their diversity in agricultural and native ecosystems. Using a combination of pan trapping and observation plot surveys, we assessed bombyliid and syrphid diversity at Bilpin, New South Wales, Australia, an important horticultural area within the Greater Blue Mountains World Heritage Area. Five syrphid species made up 62% of all individuals collected, while 22 species made up the remaining 32%, including nine species of Bombyliidae. The hover fly Melangyna viridiceps alone accounted for a third of all captured specimens. The larvae of the five most commonly encountered species are all aphidophagous. As such, aphidophagous species appear to be numerically dominant, and this is consistent with previous studies in south-east Australian agroecosystems. M. viridiceps and Triglyphus fulvicornis were frequent visitors to flowering fruit trees and may therefore contribute to the pollination of these crops. However, most visited flowers were introduced weeds or escaped crop plants. The maintenance of diverse floral resources, which may include weeds, is important for sustaining populations of aphidophagous Syrphidae, which may contribute to both pollination and pest control. As a consequence, we recommend a more tolerant approach to weed management in orchards to better facilitate the ecosystem services provided by Diptera.