what factors limit fruit production in the lowbush ... · bumble bees buzz (specialist) honey bees...

What factors limit fruit production in the lowbush blueberry, Vaccinium angustifolium?

Melissa Fulton and Linley Jesson

University of New Brunswick

Barriers to fruit production

Pollen limitation

Fruitset

Resources

Genetics

Nutrients

Disease

Pollen quantity

Pollen quality

Pollinator abundance -specialists -generalists

Pollinator behaviour -specialists -generalists

Lowbush blueberry

Specialist flower: Vibrate anthers to release pollen (buzz pollination)

Vaccinium angustifolium

Linley Jesson Linley Jesson

Duncan MacGillivray

Duncan MacGillivray

Bumble bees buzz (specialist) Honey bees cannot buzz (generalist)

Leafcutters cannot buzz (generalist)

Duncan MacGillivray

All 3 bees are used as managed pollinators

Robyn Shortt

Does pollen quantity limit reproduction (fruitset)? Do managed pollinators affect blueberry reproduction? If so, which pollinators? How do pollinators forage in blueberry fields and how might their behaviour affect fruit production?

Pollen limitation Pollen deposition (Neguac 2010 & 2011)

Neguac

St. Stephen 2009 & 2010: Honeybees

2010 & 2011 Bumblebees Leafcutters Honeybees & all combinations

- Open pollination

- Supplemental pollen

(outcross pollen)

Fru

itset

Pollen quantity Pollen quality

Clone shoots

mean of all populations per region

n=10

Pro

port

ion F

ruitset

n=10 n=24 n=24

Open Supplemental mean +/- SE

Does pollen quantity limit reproduction (fruitset)? yes Do managed pollinators affect blueberry reproduction? If so, which pollinators? How do pollinators forage in blueberry fields and how might their behaviour affect fruit production?

Neguac 2010 & 2011

Pollen limitation not reduced by managed pollinators

Late season

Early season

C control

B bumble

H honey

L leafcutter

& all combinations

H p<0.05

HB p<0.05

s

tig

mati

c p

oll

en

lo

ad

population Neguac 2010 & 2011

Late season

Early season

C control

B bumble

H honey

L leafcutter

& all combinations

H p<0.05

HB p<0.05

s

tig

mati

c p

oll

en

lo

ad

population Neguac 2010 & 2011

High pollen deposition But still pollen limited Pollen Quality

Weak effect of native pollinator abundance on fruitset

Count of honeybees per 20 min Count of Andrena per 20 min

Does pollen quantity limit reproduction (fruitset)? yes Do managed pollinators affect blueberry reproduction? If so, which pollinators? very weak effect native pollinators How do pollinators forage in blueberry fields and how might their behaviour affect fruit production?

Honey bee Bumble bee Leafcutter bee

Tukey contrasts: Bombus - Apis = 0.6 Megachile - Apis <0.0001 Megachile - Bombus <0.0001 Visits: Honey 59/hour Bumble 89/hour Leafcutter 10/hour

Flo

wers

per

inflore

scence

Does pollen quantity limit reproduction (fruitset)? yes Do managed pollinators affect blueberry reproduction? If so, which pollinators? very weak effect native pollinators How do pollinators forage in blueberry fields and how might their behaviour affect fruit production? most metrics of bee behaviour similar

Pollen limitation

Fruitset

Resources

Genetics

Nutrients

Disease

Pollen quantity

Pollen quality

Pollinator abundance -specialists -generalists

Pollinator behaviour -specialists -generalists

Su

pp

lem

en

tal fr

uit

set

Open fruitset

Regional variation indicates other factors

mean for each population (68 fields)

St. Stephen 2009 St. Stephen 2010 Neguac 2010 Neguac 2011

p<0.00001

Su

pp

lem

en

tal fr

uit

set

Open fruitset

mean for each population (68 fields)

St. Stephen 2009 St. Stephen 2010 Neguac 2010 Neguac 2011

p<0.00001

Regional variation indicates other factors

Disease Resource availability Native pollinator regimes Genetics - pollen viability, plant vigour

Significance of research

Adding generalist pollinators :

weak or no effect (on FS and PL)

Adding specialist pollinators:

no obvious effect (on FS and PL)

Native pollinators having important

contribution?

Likely significant role of selfing in

reducing fruitset

Duncan MacGillivray

Bumblebees

Leafcutters

Honeybees

Robyn Shortt

Thank You