Download - Ecological Mechanisms of Adaptation in Red Squirrels Andrew McAdam Michigan State University
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Ecological Mechanisms of Adaptation in Red Squirrels
Andrew McAdamMichigan State University
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Ecological and Evolutionary Functional Genomics (EEFG)
Genes Genotype Phenotype Phenotype’
Evolution
Q. Gen
etics
Genom
ics
Develo
pmen
t
Selecti
on
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Integrating Evolutionary Approaches
Genes Genotype Phenotype
Q. Gen
etics
/
Genom
ics
Develo
pmen
t
Selecti
onGenotype Phenotype Phenotype’
Evolution
Tradit
ional
Q. Gen
etics
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"What we understand best about evolution is mostly genetic, and what we understand least is mostly ecological."
- E.O. Wilson
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Integrating Evolutionary Approaches
Genes Genotype Phenotype
Q. Gen
etics
/
Genom
ics
Develo
pmen
t
Selecti
onGenotype Phenotype Phenotype’
Evolution
Tradit
ional
Q. Gen
etics
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Kluane Red Squirrels
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Feeding Observations
Cones
Buds
Needles
Mushrooms
'Animal Matter'
Other
n = 15,309
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3m
~450 trees distributed systematically
Monitored since 1988
Spruce Cone Counts
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Variation in Spruce Cone Abundance
0
1
2
3
4
5
6
1988 1990 1992 1994 1996 1998 2000 2002 2004
ln (
co
un
t +
1)
Year: F15, 4337 = 312.3, P <0.001dbh: F1, 452 = 90.0, P <0.001
457 trees counted in multiple yearsChecked for changes in tree id and dbh
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0
20, 000
40, 000
60, 000
80, 000
100, 000
120, 000
140, 000
160, 000
1988
1990
1992
1994
1996
1998
2000
2002
2004
Con
es p
er s
quirr
el
1 year RMR
ln(cones/tree) = 1.185 x ln (cone count); Jalene15 trees in 5m radius = 1401 trees/ha; midden conditionTerritory size = 0.2ha; Jalene
80 seeds/cone2.2 mg/seed6.62 kcal/g4.2 kJ/kcal=4.89 kJ/cone
1 year 4x RMR
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Winter
Summer
Reproduction
Cone Production
All squirrels conceive prior to the arrival of current year cones
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Food abundance influences…
Population density Sullivan 1990
Reproductive rate Sullivan 1990?
Juvenile growth rate Boutin & Larsen & 1993
McAdam & Boutin 2003a,b
Parturition date Réale et al., 2003
Bequeathal behaviour Berteaux & Boutin 2000
Juvenile survival Klenner & Krebs 1991
Humphries & Boutin 2000
McAdam & Boutin 2003a
Costs of reproduction Humphries & Boutin 2000
Ignore what you read in Larsen et al., 1997
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Food abundance also influences…
Variation in growth McAdam & Boutin 2003b
Selection on growth McAdam & Boutin 2003a
Selection on
parturition date?? Réale et al., 2003
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Hypothesis:The abundance of spruce cones is an ecological mechanism of adaptation in red squirrels.
Selection on red squirrel life history traits (e.g. parturition date, growth rates) is controlled by the abundance of food.
Annual variation in the abundance of spruce cones results in fluctuations in natural selection that minimize sustained evolutionary responses to selection.
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Conceptual Model
Conest-1
Conest
SelectionPopulationParameters(competition)
Food Abundance
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Food abundance affects territory vacancies
Vacancies estimated from changes in population density in core areasOver-winter (OW) vacancies = fall (t-1) - spring (t)New vacancies = fall (t) - fall (t-1)
OW New
r2 = 0.30, n = 16, P = 0.03 r2 = 0.49, n = 16, P = 0.002
2000
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Food affects offspring production
• Age at first reproduction - Boutin et al., unpub.
• Reproductive rate - Boutin et al., unpub.
• Litter size
All influenced by future and not previous year’s cones
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Food affects litter size
1081 litters16 years
Factor est. se df t P
Conest 0.13 0.04 13 3.2 0.007
Conest-1 0.03 0.04 13 0.7 0.51
Age 0.24 0.07 1063 3.5 < 0.001
Age2 - 0.03 0.01 1063 - 3.3 < 0.001
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Conceptual model
Conest-1
Conest
OW vacancies
- 0.11New
Territories
# Competitors
+*
-*
+**
+*
+*
=> Selection?
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~25 Days~25 Days
Nestling Growth Rate
(g/day)
1-2 Days1-2 Days
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Food affects offspring growth rates
Factor est. se df t P
Conest-1 0.13 0.023 14 5.7 < 0.001
Food Add 0.76 0.126 1400 6.1 < 0.001
Sex 0.04 0.011 1400 3.8 < 0.001
Conest-1 x Food Add - 0.29 0.039 1400 - 7.4 < 0.001
2167 offspring764 dams within years16 years
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Conceptual model - Growth
Conest-1
Conest
OW vacancies
Selection- 0.11
New Territories
# Competitors
+*
-*
+**
+*
+*
-**
-**
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Parturition Date
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Food affects timing of breeding
n = 16 years
Factor est. se df t P
Conest 1.99 1.14 13 1.7 0.10
Conest-1 -10.57 1.14 13 - 9.3 < 0.001
Age -11.40 1.24 1279 - 9.2 < 0.001
Age2 1.25 0.17 1279 7.3 < 0.001
1297 litters16 years
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Selection on Parturition Date
Factor est. se df t P
OW vac. 0.41 0.21 13 2.0 0.07
NEW vac. 0.28 0.15 13 1.9 0.08
…also positive effects of mean parturition date and year
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Conceptual model - Parturition date
Conest-1
Conest
OW vacancies
Selection- 0.11
New Territories
# Competitors
+*
-*
+**
+*
+*
+’
+’
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Goal:
To perform a replicated food supplementation experiment across multiple generations to test the hypothesis that food abundance controls life history adaptation in red squirrels
•Mimic ‘mast’ conditions for all individuals in each of 3 populations for the next 5 years
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Kluane Red Squirrel Experiment
0
20, 000
40, 000
60, 000
80, 000
100, 000
120, 000
140, 000
160, 000
1988
1990
1992
1994
1996
1998
2000
2002
2004
Con
es p
er s
quirr
el
2006
2008
2010
2012
2014
food addition
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Kluane Red Squirrel Experiment
0
20, 000
40, 000
60, 000
80, 000
100, 000
120, 000
140, 000
160, 000
1988
1990
1992
1994
1996
1998
2000
2002
2004
Con
es p
er s
quirr
el
2006
2008
2010
2012
2014
8 kgpeanut butter
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• One experimental population
• 49 females
• 100 middens supplemented
• 1kg peanut butter added to
each feeder in October 2004
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NSF Plan• Add 2 (or 3) new grids
– (SU, KL, AG, Food1, Food2, Control?)
• Supplement all individuals (~100) on each food grid
• Follow standard monitoring protocol– Add 2 (or 3) spring technicians– Add 2 or 3 grad students– Add 2 or 3 summer assistants
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Quantitative predictions based on correlations from the past 17 years of data.
Response Control (± se) ExperimentFood (ln count+1) 2.4 ± 0.4 4.0 ± 0.0
Fall density (sq./ha) 2.6 ± 0.2 3.0??
OW vac. (ha-1) 0.32 ± 0.11 0.15
New vac. (ha-1) - 0.02 ± 0.16 0.0
Litter size 3.0 ± 0.06 3.2?
Parturition date (Julian) 117.6 ± 4.1 101.1
Growth rate (g/day) 1.81 ± 0.05 2.0
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Conceptual Model
Conest-1
Conest
SelectionPopulationParameters(competition)
Food Abundance
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Quantitative Genetic Predictions - Growth
Scenario Conest Conest-1
Predicted
h2
Response
(g·day-1/gen)
1 0 4 0.62 0.57 0.18
2 4 4 0.22 0.57 0.06
3 - - 0.58 0.57 0.17
1994 0.69 4.18 0.37 0.57 0.10
Predicted response of 0.12 - 0.36 sd/gen
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Predicted changes in growth rates
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Quantitative Genetic Predictions - Parturition Date
Scenario Conest Conest-1
Predicted
h2
Response
(days/gen)
1 0 4 - 0.34 0.16* - 0.98
2 4 4 - 0.13 0.16* - 0.38
3 - - - 0.29 0.16* - 0.85
1994 0.69 4.18 - 0.73 0.16* - 2.13
Réale et al. 2003
- - - 0.24 0.16* - 0.70
* Effects of food addition are unknown
Predicted response of 0.02 - 0.05 sd/gen
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Predicted changes in parturition date
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Test Predictions
• Selection– Adults: lifetime selection – Juveniles: survival to breeding age– Adults: offspring surviving to spring
• Evolution– Phenotypic changes (corrected / common garden)– Changes in breeding values (animal model)
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Sub-projects
• Experimental and observational approaches to Genotype x Environment
• Local adaptation, gene flow and introgression• Inbreeding and outbreeding depression• Adaptation of energy acquisition and
expenditure