POLLINATORS POLLINATION AND FOOD PRODUCTION

THE ASSESSMENT REPORT ON POLLINATORS, POLLINATION AND FOOD PRODUCTION
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3. THE STATUS AND TRENDS IN POLLINATORS
AND POLLINATION
of plants from 172 families have been reported as being
visited by flies (Kearns, 2001, 2002; Inouye et al., 2015). One
species is even available commercially for pollination; Lucilia
sericata (common green bottle fly) are available as “Natufly”.
Flies are particularly important at high latitudes (Totland,
1993; Woodcock et al., 2014) and high altitudes, especially
in areas where bumble bees are not present, such as alpine
Australia (Inouye and Pyke, 1988).
Despite their obvious importance, there are very few data
available on population sizes and trends. Keil et al. (2011)
looked for temporal change in species richness of hoverflies
(Syrphidae) from the UK and the Netherlands, comparing
museum specimen data prior to and post 1980. They were
particularly interested in the effects of spatial scale, and
compared grid resolutions from 10 x10 km to 160x160 km.
Trends differed across spatial scales, but species richness
increased in the Netherlands and decreased in the UK at
the fine scale (10x1 0km), while trends differed between
countries at the coarsest scale (positive in UK, no change
in Netherlands). Thus Keil et al. (2011) concluded that
explicit considerations of spatial (and temporal) scale are
essential in studies documenting past biodiversity change or
attempting to forecast future changes.
The Delhi Sands Flower-Loving Fly (Rhaphiomidas
terminatus abdominalis) is one of the most endangered
animals on the planet and was listed under the US
Endangered Species Act in 1993 (http://www.xerces.org/
delhi-sands-flower-loving-fly/). It is a habitat specialist, and
the dunes where it occurs in southern California have largely
disappeared due to development. The flies collect nectar
of at least one plant in that habitat (Eriogonum fasiculatum)
(U.S. Fish and Wildlife Service, 1997).
Iler et al. (2013) analysed a 20-year record of Syrphidae from
a Malaise trap maintained at the Rocky Mountain Biological
Laboratory (2,900 m altitude in Colorado, USA). Their primary
focus was on phenology of fly emergence (several species),
for which they found no significant trend, suggesting that
the historic interaction with food plants is being maintained
in the face of climate change. A 15-yr study of Syrphidae
in the UK (Owen, 1989) found that hoverfly populations
are more stable than those of other terrestrial arthropods,
that there are strong correlations (r=0.51-0.54, p