ALIEN IMPACT

4. Plant-pollinator interactions Methodological approaches from the

field to an experimental design

Layla SAAD, Anne-Laure JACQUEMART, Grégory MAHY, Julie LEBRUN & Valérie CAWOY

ALIEN IMPACT

Plant-pollinator interactions

Competition Facilitation

Key elements to consider for studying plant-pollinator interactions:

Invasive speciesPresence-absenceDensity

Pollinators sharingFrequency of visits Efficiency of pollinators

Effect on native species seed set

Native speciesPlant phenologyPlant reproductive success

ALIEN IMPACT

Two methodological approaches

I. Pollination web in the field

Solidago giganteaFallopia spp.

Senecio inaequidensImpatiens glandulifera

II. Outdoor controlled competition experiments with potted plants

Study sites

3 sites per target HIPS

Permanent transect (2X10 m) including the target HIPS and adjacent native species community

I. Pollination web

12

3

4

5

ALIEN IMPACT

I. Pollination web

Visitors observations

Each plant-insect interaction recorded :

- precise identification for the plant species

- category identification for the insect species

Green fly

x

Solidago gigantea

Large hoverfly

x

Origanum vulgare

ALIEN IMPACT

Solidago gigantea

Rosières Solidago gigantea pollinator guild

Flies16%

Other diptera46.5%

Hoverflies21%

APIMEL

OTHHYM

VESPOI

HOVLAR

HOVSMA

HELOPH

FLIES

DIPMIC

OTHDIP

HEMIPT

OTHERS

Site 1

Bibionidae

ALIEN IMPACT

Site 3Site 2

Solidago gigantea visitor guild

Pollination web – Results

ALIEN IMPACT

627 interactions

Pollination web

Between 300 and 3000 plant-pollinator interactions recorded in the communities

12 plant species 14 insect categories

EUPCAN 56.06FILULM 53.59MENAQU 47.72EPIHIR 40.6LYCEUR 39.32CIRPAL 32.38LYTSAC 32.29STAPAL 29.41EPISPP 15.36CALSEP 0STAOFF 0

Proportional similarity

Pollination web – Results

ALIEN IMPACT

RixensartProportional number of visits recorded

14%

14%

Solidago44%

CALSEP

CIRPAL

EPIHIR

EPISPPEUPCAN

FILULM

LYCEUR

LYTSAC

MENAQU

SOLGIG

STAOFF

STAPAL

Frequency of visits

Between 35% and 57% of all visits recorded in the communities were on Solidago gigantea

627 interactions

Pollination web

Between 300 and 3000 plant-pollinator interactions recorded in the communities

12 plant species 14 insect categories

EUPCAN 56.06FILULM 53.59MENAQU 47.72EPIHIR 40.6LYCEUR 39.32CIRPAL 32.38LYTSAC 32.29STAPAL 29.41EPISPP 15.36CALSEP 0STAOFF 0

Proportional similarity

Pollination web – Results

ALIEN IMPACT

15 m

55 m 55 m

15 m 15 m

0 m - 25 HIPS

15 m - 25 HIPS 15 m - 5 HIPS

0 m - 5 HIPS 0 m - 0 HIPS

15 m - 0 HIPS

II. Controlled experiments - Experimental design

ALIEN IMPACTControlled experiments - Invasive-native pairs

Aconitum napellus subsp. lusitanicum

2

Epilobium angustifolium

1

Impatiens glandulifera Impatiens glandulifera

Jacobaea vulgaris (Senecio jacobaea)

3

Senecio inaequidens

http://www.biopix.dk/Species.asp?Searchtext=Aconitum napellus ssp. lusitanicum&Category=Planter

Impatiens glandulifera & Epilobium angustifolium

ALIEN IMPACT

Controlled experiments – Results

Number of visitorsObservation periods of

10 min

Visitor number (10-min period) - Site B

0

2

4

6

8

10

12

14

16

18

0 HIPS 5 HIPS 25 HIPS 0 HIPS 5 HIPS 25 HIPS

0 m between invasive - native 15 m between invasive - native

Num

ber o

f vis

itors

per

10-

min

per

iod Facilitation

ALIEN IMPACT

Controlled experiments – Results

Number of visitorsObservation periods of

10 min Visitors categories

Total visitor number - Site B

0

50

100

150

200

250

300

0 HIPS 5 HIPS 25 HIPS 0 HIPS 5 HIPS 25 HIPS

0 m between invasive - native 15 m between invasive - native

Num

ber o

f ins

ects

Honeybee Bumblebee Other insect

Facilitation: bumblebees (main visitor of HIPS)

ALIEN IMPACT

Controlled experiments – Results

Number of visitorsObservation periods of 10 min Visitors categories

Sampling flowers

HIPS pollen deposited ?Quantity of conspecific pollen

HIPS

Native

One stigmatic lobe - 6 flowers (means)

0

200

400

600

800

1000

0 HIPS 5 HIPS 25 HIPS

0 m between invasive - native

Num

ber o

f pol

len

grai

ns

Conspecific HIPS Others

- 26%

http://www-saps.plantsci.cam.ac.uk/pollen/pollen/pages/Impatiens tinctoria1.htmhttp://www-saps.plantsci.cam.ac.uk/pollen/pollen/pages/Chelidonium magus.htm

ALIEN IMPACT

Controlled experiments – ResultsNumber of visitorsObservation

periods of 10 min Visitors categories

Sampling flowers

HIPS pollen deposited ?Quantity of conspecific pollen

Sampling fruits Seed set

Seed set - Site A

0

0.2

0.4

0.6

0.8

1

0 HIPS 5 HIPS 25 HIPS

0 m between invasive - native

Num

ber o

f rip

e se

eds

/ nu

mbe

r of o

vule

s

no pollen limitation (560 ovules per ovary and at least 1260 conspecific pollen grains deposited)

ALIEN IMPACT

Plant-pollinator interactionsConclusions

• Impacts on the pollinator services mainly detected when native and invasive species were nearby• Impacts on the pollinator services proportional to the number of invasive individuals• No impact on the reproductive success of the native species

Controlled experiments

Pollinator web• Integration of invasive species into the community pollinator web• More visits to HIPS than to native species

Thank you for your attention…

Acknowledgements

GPEX (plant transport)

Colleagues and students (data collection)

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