1. IV. Life History Evolution Trade-Offs
Components of fitness?
- probability of survival
- number of offspring
- probability that offspring survive

2. IV. Life History Evolution Trade-Offs
2. Relationships with Energy Budgets
METABOLISM
GROWTH
SURVIVAL
METABOLISM
REPRODUCTION
REPRODUCTION

3. IV. Life History Evolution Trade-Offs
3. Trade-offs Between Survival and Reproduction
Maximize probability of survival
Maximize reproduction
GROWTH
METABOLISM
GROWTH
REPRODUCTION
METABOLISM
REPRODUCTION

4. IV. Life History Evolution Trade-Offs
3. Trade-offs Between Survival and Reproduction
Add 2 chicks. Fledge an additional 0.75 chicks, at a cost of 10% decrease in survivorship
European Kestrels

5. IV. Life History Evolution Trade-Offs
3. Trade-offs Between Survival and Reproduction
Cox, R.M., and R. Calsbeek Severe costs of reproduction persist in Anolis lizards despite the evolution of a single-egg clutch. Evolution 64:

6. IV. Life History Evolution Trade-Offs
3. Trade-offs Between Survival and Reproduction
Having a second offspring increases reproductive success by 100%. Moving from 4 offspring to 5 only increases fitness by 25%, but the cost of that 5th offspring is the same as the cost of the second.

7. IV. Life History Evolution Trade-Offs
3. Trade-offs Between Survival and Reproduction
- Suppose the probability of adult survival is low for other reasons?
Can wait
Can’t wait

8. IV. Life History Evolution Trade-Offs
3. Trade-offs Between Survival and Reproduction
- Suppose the probability of adult survival is low for other reasons?
Can vary within a species in different environments: Guppies

9. IV. Life History Evolution Trade-Offs
4. Trade-offs Between # offspring and offspring survival
METABOLISM
REPRODUCTION
REPRODUCTION
METABOLISM
A few large, high prob of survival
Lots of small, low prob of survival

10. IV. Life History Evolution Trade-Offs
4. Trade-offs Between # offspring and offspring survival
Decrease size, decrease probability of survival

11. IV. Life History Evolution Trade-Offs
4. Trade-offs Between # offspring and offspring survival – Lack Hypothesis
Decrease size through decreased parental care, decrease survival
Again, diminishing returns, then net cost
Laid
Fledged
Diff. 5
2.25 6 3
0.75 7
3.5
0.50 8
-1.25

12. IV. Life History Evolution Trade-Offs
4. Trade-offs Between # offspring and offspring survival – Lack Hypothesis
Varies within a species under different environmental conditions: Guppies

13. IV. Life History Evolution Trade-Offs Timing
1. First Age of Reproduction
2. Parity: How Often to Reproduce
- Semelparous vs. iteroparous
Semelparity = once
Iteroparity = iterative… many

14. IV. Life History Evolution Trade-Offs Timing
1. First Age of Reproduction
2. Parity: How Often to Reproduce
- Semelparous vs. iteroparous
Variable environment; “all in” when favorable may not get another chance
Benign environment; no need to sacrifice future reproduction.

15. III. Life History Evolution Trade-Offs Timing
1. First Age of Reproduction
2. Parity: How Often to Reproduce
3. Senescence
- Why age?
- Accumulation of mutations
- Cost of DNA repair late in life vs. expending
that energy in reproduction earlier in life.
Why do human have a long post-reproductive period?
The ‘grandmother effect’
Lahdenpera et al., Nature.
Finland, 1702–1823, (6,002 grandchildren born). Canada, 1850 to 1879 ,(100,074 grandchildren born)

16. III. Life History Evolution Trade-Offs Timing Life History Strategies
Unstable environment, density independent K
Stable environment, density dependent interactions
small size of organism
large size of organism
energy used to make each individual is low
energy used to make each individual is high
many offspring are produced
few offspring are produced
early maturity
late maturity, often after a prolonged period of parental care
short life expectancy
long life expectancy
each individual reproduces only once
individuals can reproduce more than once in their lifetime
type III survivorship pattern in which most of the individuals die within a short time but a few live much longer
type I or II survivorship pattern in which most individuals live to near the maximum life

17. III. Life History Evolution
Trade-Offs
Timing
Life History Strategies

18. III. Life History Evolution Trade-Offs Timing Life History Strategies
Effects of Humans
Tree swallows breed 9 days earlier in North America; salamanders in Britain bred 7 weeks earlier! Correlates with mean temperature.

19. III. Life History Evolution Trade-Offs Timing Life History Strategies
Effects of Humans
Flowerin gof 42 plants in Concord, MA, is an average of 7 days earlier than when recorded by Thoreau in 1852, and mean temp is 2.4oC higher (~ 4oF).

20. III. Life History Evolution
Trade-Offs
Timing
Life History Strategies
Effects of Humans

21. Selection for earlier age of maturity, too.