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