Assessing the hoverfly populations at Primley Meadow and Clennon grassland and their
interactions with the wildflower communities
Hannah Sutton1, 2 and Tracey Hamston2
1 University of Plymouth, Plymouth, PL4 8AA, UK2Whitley Wildlife Conservation Trust, Paignton, TQ4 7EU
Study sites
Primley Meadow
Clennon Grassland
Why study hoverflies?• Hoverflies are in the order Diptera, currently there are 283 species described in the British
Isles and 6,000 worldwide (Ball & Morris, 2015).
• Alongside bees, they provide pollinator services.
• Some hoverfly larvae control pests.
• Batesian mimicry, is a characteristic that hoverflies exhibit to mimic the markings of bees and wasps.
• They are mainly warning colours to reduce predation.
© Steven Falk, Flickr
Hoverfly WaspBumblebee
©Imgarcade © A-Z animals
Hoverfly larvae feeding on an aphid
©enacademic
Hoverfly foraging behaviours
• Hoverflies tend to feed on open flowers due to the food resources being easily accessible.
• Generally larger hoverflies tend to feed on nectar due to the high energy content.
• However they can feed on pollen and it has been suggested that pollen is needed by females for ovarian development.
(Gilbert, 1981)
© WordpressDusting of pollen
Pollen on their face
Aims: To compare the hoverfly communities and foraging patterns of the two grassland sites
Questions:
1. Do the hoverfly communities of calcareous grassland and semi-improved grassland differ?
2. What are the foraging preferences of the hoverflies present at the sites?
Method: Setting up transects
Hoverfly transects Flower transects
Three 50m transects were set up on each site
Environmental variables were recorded
Record every individual present in the transect(Tally counter used for flowers)
Identification to genus level Estimated the flowers on flowering trees like hawthorn
Collection pots used for closer identification
Photos were taken and wildflower guides used for identification
Data analysis - Bipartite Package in R
Aerial map of the 50m transects
B
A
E
Clennon Grassland
D
CF
Primley Meadow
Results: Numbers of foraging hoverflies
W = 31.5p-value = 0.002
No.
of h
over
flies
fora
ging
SiteN
o. o
f hov
erfli
es fo
ragi
ngHabitat
No significancep-value = 0.571
Results: Clennon Visitation Networks
Many of the interactions were only with one individual which is reflected in the thickness of the bands.
Plan
t Spe
cies
Hoverfly Species
Total no. of foraging hoverflies = 24
Results: Primley Visitation Networks Total no. of foraging hoverflies = 182
• A Total of 13 different hoverfly species interaction with 6 flower species.
• Multiple interactions with meadow buttercup.
• Some hoverfly species were interacting with 5 flower species.
Plan
t Spe
cies
Hoverfly Species
I
II
I
II
I
I
II
I
II
Results: Generalised linear models
Variable Df LRT (χ2) Pr(>Chi) Significance
<none>
Site 1 110.592 < 2.2e-16 High (0***)
Cloud cover (%) 1 92.440 < 2.2e-16 High (0***)
Flower diversity (Simpsons, D) 1 28.164 1.115e-07 High (0***)
Temp:Abun.flowers (Nested) 1 34.941 3.399e-09 High (0***)
Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
• Likelihood ratio test table• Compared hoverfly abundance with four variables• They are all highly significant• Nested terms – temperature and abundance of flowers
Aims: To compare the hoverfly communities and foraging patterns of the two grassland sites
Questions:
1. Do the hoverfly communities of calcareous grassland and semi-improved grassland differ?
2. What are the foraging preferences of the hoverflies present at the sites?
Discussion
• As a whole both sites had a similar number of hoverfly species with eight species seen at both sites.
• Many more foraging individuals at Primley than Clennon.
• Melanogaster sp. frequently fed on buttercup species at Primley, in comparison to Clennon where only 3/5 foraging individuals fed on buttercup.
• Many of the other species, like Cheilosia sp., were recorded on multiple flowering species at both sites.
• It seems that the hoverflies vary in their foraging patterns and looks to feed on what is available and in the case of Primley, the most abundant flower source.
• Looking at hoverfly species diversity other influences could play a part.
Further Research• Setup more or longer transects to get an more even representation.
• Compare to other grassland sites, especially calcareous to see if Clennon is representative
• Could look at specific species and follow individual foraging routes, which would achieve more detailed data.
• Prolonged data collection period to observe more changes in the flowering communities.
• Further research will be able to highlight the most important flower species for hoverfly communities which can be taken in consideration when site management is carried out.
Acknowledgements
With thanks to the Field Conservation and Research department in particular Tracey Hamston and Dave Ellacott.
All my fellow placement students including Angie Shek for support with data collection.
Thank you for ListeningReferences
• Ball, S. & Morris, R. (2015) Britain’s Hoverflies: A field guide. Princeton University Press: Oxfordshire.
• Carvell et al. (2007) Comparing the efficacy of agri-environment schemes to enhance bumble bee abundance and diversity on arable field margins, Journal of Applied Ecology, 44, 29-40.
• Gilbert, F. (1981) Foraging ecology of hoverflies: morphology of the mouthparts in relation to feeding on nectar and pollen some common urban species, Ecological Entomology, 6, 245-262.
© Matt Cole photography