Example
– Physiological trade-offs
– Evolutionary trade-offs
8.5
6000
8
5000
7.5
4000
fecundity
• Links between traits limiting simultaneous
evolution of both traits.
• May be:
egg diameter
Trade-offs
7
6.5
2000
6
• Can be measured by
– Selecting on one traint and observing the response in
another traits (between generations)
– Manipulating the phenotype of an individual and
observe the consequences (within individual)
3000
1000
400
500
600
Length
700
800
400
500
600
Length
700
800
Coho salmon Oncorhynchus kisutch
Vøllestad et al. Unpubl.
Example
Example
Brown trout Salmo trutta
1200
1000
Life span
(degree-days)
Residuals egg diameter
1
0
800
600
400
200
0
.01
.02
.03
.04
Growth rate (mm/degree-day)
-1
-2000
-1000
0
1000
Residuals fecundity
2000
Vøllestad and Lillehammer 2001
1
Example
Rohmer 1967
Type of trade-offs
• Physiological trade-off
Growth
R = -0.54
– Allocation rules: prosesses that compete for resourses
within individuals.
• Microevolutionary trade-offs
– Within the population; includes physiological trade-offs
Seed yield
• Macroevolutionary trade-offs
– Between populations, species, genera, families: the
same as ”line-specific” effects.
Reproduction vs growth
Beech Fagus sylvatica
Physiological trade-offs
A simplified model
Growth
u
Intake
Faeces
Digested
Excretion
Metabolised
Heath
COSTS
Surplus
power
Fitness
1-u
Reproduction
Net assimilated
Standard metabolism
Surplus”
Activity metabolism
GROWTH
Investment REPRODUCTION
For every u there
is one estimate of
fitness
Fitness
u*
u, allocation
to growth
2
A somewhat more difficult model
Fitness-isoclines
Micro-evolutionary trade-offs
Unlimited optimum
•
•
Growth
1.
2.
3.
4.
5.
Limited optimum
•
Reproduction
Trade-off with slope -1
Growth = 1 - Reproduction
Trade-off within individual - or between
generations (parent - progeny conflict)
A(energy acquired) = R(reproduction) + S(survival)
Ri = Bi Ai
• Traits are fixed because of evolutionary
history
• Income vs. capital breeders
• Use and distribution of energy
• Genotype x Environment interactions
Reproduction vs. survival
Reproduction vs. future reproduction
Reproduction vs. growth
Reproduction vs. condition
Number vs. size of progeny
Acquisition and use of energy
”Wrong” trade-off function is
often observed!
– No trade-off will be observed between
reproductive investment and growth in income
breeders (we are measuring wrong costs)
Can include physiological trade-offs (but need
not)
Some often tested trade-offs:
Among-individual variation
in allocation
B2
S
B1
R
A=1 A=2
Among-individual
variation in acquisition
Si = (1 - Bi)Ai
Van Noordwijk and de Jong 1986
3
Reproductive investment
Genotype x Environment interaction:
More examples
Environment A
rg < 0
Meadow grass/Tunrapp Poa annua
Law et al. 1979
no genetic correlation
rg > 0
Drosophila males
Partridge and Farquhar 1981
Total environmental variation
Environment B
Adult survival
Notiophilus biguttatus (Carabidae)
How does a trade-off function
look like?
•
•
•
•
Linear
Concave
Convex
More complicated?
Ernsting and Isaaks 2000
4
Three main questions to be
asked:
– Is the slope positive or negative?
– What kind of shape?
– Interactions?
• Environmental variables
• Other traits?
– Very often so
– May even mask trade-offs
5