bees are in trouble - mary myerscough
DESCRIPTION
Talk presented at Mathematics of Planet Earth Biosecurity meeting (A Planet at Risk) - Mary Myerscough Abstract. Honey bees are vital to the production of many foods which need to be pollinated by insects. Yet in many parts of the world honey bee colonies are in decline. A crucial contributor to hive well-being is the health, productivity and longevity of its foragers. When forager numbers are depleted due to stressors in the colony (such as disease or malnutrition) or in the environment (such as pesticides) there is a significant effect, not only on the amount of food (nectar and pollen) that can be collected but also on the colony's capacity to raise brood (eggs, larvae and pupae) to produce new adult bees to replace lost or aged bees. We use a set of differential equation models to explore the effect on the hive of high forager death rates. In particular we examine what happens when bees become foragers at a comparatively young age and how brood rearing, food collection and colony survival is impacted by forager loss.TRANSCRIPT
Photo: Ben Oldroyd
“Bees are in trouble”
“Bees are in trouble”
Why?
Colony loss
Colony loss
R. Upshaw vimeo.ocm
Winter losses
Colony loss
R. Upshaw vimeo.ocm
Winter losses bees get too cold due to lack of food
or colony becomes too small to keep warm
Colony loss
Colony collapse events
no or few adult bees, no dead bees
Colony loss
Colony collapse events
capped brood (pupae) and food remain
no or few adult bees, no dead bees
Colony loss
Colony collapse events
950
1905
~1909
1975
1999
But why should we care?
But why should we care?
Honey?
But why should we care?
Honey? POLLINATION!
But why should we care?
Honey? POLLINATION!
But why should we care?
Honey? POLLINATION!
But why should we care?
Honey? POLLINATION!
But why should we care?
Honey? POLLINATION!
But why should we care?
Honey? POLLINATION!
But why should we care?
Honey? POLLINATION!
But why should we care?
Honey? POLLINATION!
Alternatives?
Alternatives?
Alternatives?
Alternatives?
Alternatives?
Alternatives?
Alternatives?
Varroa mite
Nosema
Causes of colony loss?
Varroa mite
Nosema
Causes of colony loss?
but not in Australia! (yet)
Viral diseases
Nosema
Causes of colony loss?
Varroa
Nosema
Causes of colony loss?
Causes of colony loss?
Climate change
Causes of colony loss?
Causes of colony loss?
Causes of colony loss?
Causes of colony loss?
Causes of colony loss?
Causes of colony loss?
Causes of colony loss?
What is the mechanism of hive loss?
Hypothesis: forager loss
drives hive loss
Honeybee demographics Age
eclosion
death Age-based polyethism
Social inhibition: Many foragers Hive bees stay in the hive Few foragers Hive bees become foragers
recruitment
Honeybee demographics Age
eclosion
death Age-based polyethism
Social inhibition: Many foragers Hive bees stay in the hive Few foragers Hive bees become foragers
recruitment
Honeybee demographics Age
death Age-based polyethism
Social inhibition: Many foragers Hive bees stay in the hive Few foragers Hive bees become foragers
brood
Honeybee demographics Age
eclosion
death Age-based polyethism
Social inhibition: Many foragers Hive bees stay in the hive Few foragers Hive bees become foragers
brood hive bee
Honeybee demographics Age
eclosion
death Age-based polyethism
Social inhibition: Many foragers Hive bees stay in the hive Few foragers Hive bees become foragers
recruitment
brood hive bee
forager
Honeybee demographics Age
eclosion
death Age-based polyethism
Social inhibition: Many foragers Hive bees stay in the hive Few foragers Hive bees become foragers
recruitment
brood hive bee
forager
Honeybee demographics Age
eclosion
death Age-based polyethism
Social inhibition: Many foragers Hive bees stay in the hive Few foragers Hive bees become foragers
recruitment
brood hive bee
forager
Honeybee demographics Age
eclosion
death Age-based polyethism
Social inhibition: Many foragers Hive bees stay in the hive Few foragers Hive bees become foragers
recruitment
brood hive bee
forager
Honeybee demographics Age
eclosion
death Age-based polyethism
Social inhibition: Many foragers Hive bees stay in the hive Few foragers Hive bees become foragers
recruitment
brood hive bee
forager
Honeybee demographics Age
eclosion
death Age-based polyethism
Social inhibition: Many foragers Hive bees stay in the hive Few foragers Hive bees become foragers
recruitment
brood hive bee
forager
Honeybee demographics
eclosion
death Age-based polyethism
Social inhibition: Many foragers Hive bees stay in the hive Few foragers Hive bees become foragers
recruitment
brood hive bee
forager
Bigger colonies raise more brood
Colony collapse demographic model
Hive bees:
Foragers:
eclosion recruitment
€
dFdt
= R(H,F) −mFrecruitment death
E(H+F) increasing, saturating function; R(H,F) =
€
α −σF
F + Hfastest maturation
social inhibition
€
dHdt
= E(H + F) −HR(H,F)
Khoury et al, 2011, PLoS ONE 6: e18491
Colony collapse demographic model
Hive bees:
Foragers: €
dHdt
= E(H + F) −HR(H,F)
eclosion
€
dFdt
= R(H,F) −mFrecruitment death
E(H+F) increasing, saturating function; R(H,F) =
€
α −σF
F + Hfastest maturation
social inhibition
Khoury et al, 2011, PLoS ONE 6: e18491
Colony collapse demographic model
Hive bees:
Foragers:
eclosion recruitment
€
dFdt
= R(H,F) −mFrecruitment death
E(H+F) increasing, saturating function; R(H,F) =
€
α −σF
F + Hfastest maturation
social inhibition
€
dHdt
= E(H + F) −HR(H,F)
Khoury et al, 2011, PLoS ONE 6: e18491
Colony collapse demographic model
Hive bees:
Foragers:
eclosion recruitment
€
dFdt
= HR(H,F) −mFrecruitment death
E(H+F) increasing, saturating function; R(H,F) =
€
α −σF
F + Hfastest maturation
social inhibition
€
dHdt
= E(H + F) −HR(H,F)
Khoury et al, 2011, PLoS ONE 6: e18491
Colony collapse demographic model
Hive bees:
Foragers:
eclosion recruitment
recruitment death
E(H+F) increasing, saturating function; R(H,F) =
€
α −σF
F + H
social inhibition
€
dHdt
= E(H + F) −HR(H,F)
€
dFdt
= HR(H,F) −mF
Khoury et al, 2011, PLoS ONE 6: e18491
€
E(H + F) = E(N) =LNN + w
maximum laying rate of queen
controls saturation rate
Khoury et al, 2011, PLoS ONE 6: e18491
Colony collapse demographic model
Hive bees:
Foragers:
eclosion recruitment
recruitment death
E(H+F) increasing, saturating function; R(H,F) =
€
α −σF
F + H
€
dHdt
= E(H + F) −HR(H,F)
€
dFdt
= HR(H,F) −mF
Khoury et al, 2011, PLoS ONE 6: e18491
Colony collapse demographic model
Hive bees:
Foragers:
eclosion recruitment
recruitment death
E(H+F) increasing, saturating function; R(H,F) =
€
α −σF
F + Hfastest maturation
€
dHdt
= E(H + F) −HR(H,F)
€
dFdt
= HR(H,F) −mF
Khoury et al, 2011, PLoS ONE 6: e18491
Colony collapse demographic model
Hive bees:
Foragers:
eclosion recruitment
recruitment death
E(H+F) increasing, saturating function; R(H,F) =
€
α −σF
F + Hfastest maturation
social inhibition
€
dHdt
= E(H + F) −HR(H,F)
€
dFdt
= HR(H,F) −mF
Khoury et al, 2011, PLoS ONE 6: e18491
Colony collapse demographic model
Hive bees:
Foragers:
eclosion recruitment
recruitment death
E(H+F) increasing, saturating function; R(H,F) =
€
α −σF
F + H
proportion of foragers in colony
€
dHdt
= E(H + F) −HR(H,F)
€
dFdt
= HR(H,F) −mF
Khoury et al, 2011, PLoS ONE 6: e18491
Colony collapse demographic model Phase plane: m = 0.1: steady state solution
Khoury et al, 2011, PLoS ONE 6: e18491
Colony collapse demographic model Phase plane: m = 0.3: colony death
Khoury et al, 2011, PLoS ONE 6: e18491
Colony collapse demographic model Time course: m = 0.35: colony collapse
Colony collapse demographic model Bifurcation diagram
death rate m
fora
ger p
opul
atio
n at
stea
dy st
ate
Khoury et al, 2011, PLoS ONE 6: e18491
eclosion
death
recruitment
Colony collapse demographic model
* Forager death rate drives population size
High death rate low social inhibition loss of hive bees loss of brood
* Colony collapse disorder may have many causes
more adult bees raise more brood
eclosion
death
recruitment
Colony collapse demographic model
* Forager death rate drives population size
High death rate low social inhibition loss of hive bees loss of brood
* Colony collapse disorder may have many causes
more adult bees raise more brood
eclosion
death
recruitment
Colony collapse demographic model
* Forager death rate drives population size
High death rate low social inhibition loss of hive bees loss of brood
* Colony collapse disorder may have many causes
more adult bees raise more brood
eclosion
death
recruitment
Colony collapse demographic model
* Forager death rate drives population size
High death rate low social inhibition loss of hive bees loss of brood
* Colony collapse disorder may have many causes
more adult bees raise more brood
eclosion
death
recruitment
Colony collapse demographic model
* Forager death rate drives population size
High death rate low social inhibition loss of hive bees loss of brood
* Colony collapse disorder may have many causes
more adult bees raise more brood
eclosion
death
recruitment
Colony collapse demographic model
* Forager death rate drives population size
High death rate low social inhibition loss of hive bees loss of brood
* BUT it gets worse…..
more adult bees raise more brood
high death rate younger foragers
age at death
age at commencement of foraging
high death rate younger foragers
high death rate younger foragers
younger foragers are less competent
higher death rates
high death rate younger foragers
younger foragers are less competent
higher death rates
standard model
including young forager incompetence
But, but, but,……
But, but, but,……
What about food?
But, but, but,……
What about food?
and brood?
eclosion
death
recruitment
Colony collapse demographic model
* Forager death rate drives population size High death rate low social inhibition loss of hive bees loss of brood
* Colony collapse disorder may have many causes
eclosion
death
recruitment
Colony collapse demographic model
* Forager death rate drives population size High death rate low social inhibition loss of hive bees loss of brood
* Colony collapse disorder may have many causes
eclosion
recruitment
Colony collapse demographic model
* Forager death rate drives population size High death rate low social inhibition loss of hive bees loss of brood
* Colony collapse disorder may have many causes
brood hive bees foragers
eggs larvae pupae (capped brood)
3 days 6 days 12 days
eclosion
recruitment
Colony collapse demographic model
* Forager death rate drives population size High death rate low social inhibition loss of hive bees loss of brood
* Colony collapse disorder may have many causes
brood hive bees foragers
eggs larvae pupae (capped brood)
12 days
food important
eclosion
recruitment
Colony collapse demographic model
* Forager death rate drives population size High death rate low social inhibition loss of hive bees loss of brood
* Colony collapse disorder may have many causes
brood hive bees foragers
eggs larvae pupae (capped brood)
12 days
consumption and cannibalism
eclosion
recruitment
Colony collapse demographic model
* Forager death rate drives population size High death rate low social inhibition loss of hive bees loss of brood
* Colony collapse disorder may have many causes
brood hive bees foragers
eggs larvae pupae (capped brood)
12 days
consumption and cannibalism
cannibalism
stored food
uncapped brood
hive bees
foragers
Hive bees, foragers, food and brood
hive bees
foragers
collection Hive bees, foragers, food and brood
uncapped brood
stored food
hive bees
foragers
collection consumption
Hive bees, foragers, food and brood
uncapped brood
stored food
hive bees
foragers
Hive bees, foragers, food and brood
brood production depends on food uncapped
brood
stored food
hive bees
foragers
eclosion
Hive bees, foragers, food and brood
and on hive bees
brood production depends on food uncapped
brood
stored food
hive bees
foragers
Hive bees, foragers, food and brood
eclosion
pupation uncapped brood
stored food
hive bees
foragers
Hive bees, foragers, food and brood
eclosion
delay
uncapped brood
stored food
hive bees
foragers
Hive bees, foragers, food and brood
social inhibition depends on food
uncapped brood
stored food
hive bees
foragers
recruitment
Hive bees, foragers, food and brood
uncapped brood
stored food
hive bees
foragers
recruitment
Hive bees, foragers, food and brood
uncapped brood
stored food
hive bees
foragers
recruitment
Hive bees, foragers, food and brood
uncapped brood
stored food
hive bees
foragers
recruitment
Hive bees, foragers, food and brood
uncapped brood
stored food
hive bees
foragers forager death
Hive bees, foragers, food and brood
uncapped brood
stored food
Hive bees, foragers, food and brood
time in days
food foragers
hive bees
brood
m = 0.1
Hive bees, foragers, food and brood
time in days
food
foragers
hive bees
brood
m = 0.3
Hive bees, foragers, food and brood
time in days
foragers
hive bees
brood
food
m = 0.42
Hive bees, foragers, food and brood
time in days
foragers
food
m = 0.5
hive bees
brood
food
brood
hive bees
foragers
where
Hive bees, foragers, food and brood
food
brood
hive bees
foragers
where
Hive bees, foragers, food and brood
food
brood
hive bees
foragers
where
Hive bees, foragers, food and brood
food
brood
hive bees
foragers
where
Hive bees, foragers, food and brood
Steady state populations
brood
food
hive bees
foragers
analytic numerical death rate m
Steady state populations
brood
food
hive bees
foragers
analytic numerical death rate m
Steady state populations
brood
food
hive bees
foragers
analytic numerical death rate m
increasing food
Steady state populations
brood
food
hive bees
foragers
analytic numerical death rate m
increasing food limited food
Steady state populations
brood
food
hive bees
foragers
analytic numerical death rate m
increasing food limited food hive dies
Steady state populations
brood
food
hive bees
foragers
analytic numerical death rate m
increasing food limited food hive dies
food remains
Steady state populations
brood
food
hive bees
foragers
analytic numerical death rate m
m = 0.1 m = 0.3 m = 0.42 m = 0.5
Steady state populations
brood
food
hive bees
foragers
analytic numerical
m = 0.1 m = 0.3 m = 0.42 m = 0.5
analytic numerical
Steady state populations
analytic numerical
food
foragers
brood hive bees
food collection rate c
Steady state populations
analytic numerical
food
foragers
brood hive bees
food collection rate c
Steady state populations
analytic numerical
food
foragers
brood hive bees
food collection rate c
hive dies
Steady state populations
analytic numerical
food
foragers
brood hive bees
food collection rate c
hive dies
limited by food
Steady state populations
analytic numerical
food
foragers
brood hive bees
food collection rate c
hive dies
limited by food
limited by brood
survival
Agreement with data
Adult bees
Khoury et al 2013 PLOS ONE
Agreement with data
Adult bees
Khoury et al 2013 PLOS ONE input
Agreement with data
Adult bees
Khoury et al 2013 PLOS ONE
Agreement with data
Brood cells
Khoury et al 2013 PLOS ONE
Agreement with data
Food
Khoury et al 2013 PLOS ONE
Agreement with data
Khoury et al 2013 PLOS ONE
Food
Agreement with data
Khoury et al 2013 PLOS ONE
Food
small colonies do worse than predicted
Population changes with increased forager death ratew
food
brood
hive bees
foragers
m = 0.1 m = 0.42
strong hive
Population changes with increased forager death ratew
food
brood
hive bees
foragers
m = 0.1 m = 0.42
perceptible change in food storage pattern and adult bee numbers
strong hive
Population changes with increased forager death ratew
food
brood
hive bees
foragers
m = 0.1 m = 0.42
perceptible change in food storage pattern and adult bee numbers
no perceptible change in brood numbers
strong hive
Population changes with increased forager death ratew
m = 0.3 m = 0.42
no perceptible changes
food
hive bees
brood
foragers
weak but
viable hive
but hive is doomed
So, does forager loss drive hive loss?
So, does forager loss drive hive loss?
Yes. It can
What else does this model suggest?
What else does this model suggest?
*Food supplies can remain even after hive loss through forager death
What else does this model suggest?
*Brood is relatively unaffected by forager loss
*Food supplies can remain even after hive loss through forager death
What else does this model suggest?
*Brood is relatively unaffected by forager loss
*Food supplies can remain even after hive loss through forager death
*Number of adult bees may be the best indicator of colony well-being
How can we protect honey bees? (and sustain our food supply)
How can we protect honey bees? (and sustain our food supply)
How can we protect honey bees? (and sustain our food supply)
* Pay attention to general hive health. It is crucial!
* Pay attention to general hive health. It is crucial!
* Take care with insecticide use
How can we protect honey bees? (and sustain our food supply)
* Pay attention to general hive health. It is crucial!
* Take care with insecticide use
* Monitor adult bee populations in hives
How can we protect honey bees? (and sustain our food supply)
* Pay attention to general hive health. It is crucial!
* Take care with insecticide use
* Maintain quarantine against varroa
* Monitor adult bee populations in hives
How can we protect honey bees? (and sustain our food supply)
Lela Dowling, Bee Culture Magazine
Lela Dowling, Bee Culture Magazine
Lela Dowling, Bee Culture Magazine
Lela Dowling, Bee Culture Magazine
Lela Dowling, Bee Culture Magazine
Lela Dowling, Bee Culture Magazine
Lela Dowling, Bee Culture Magazine