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
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

5. IV. Life History Evolution Trade-Offs
5. Examples

6. IV. Life History Evolution Trade-Offs
5. Examples
European Kestrels

7. IV. Life History Evolution Trade-Offs
5. Examples
- Suppose the probability of adult survival is low for other reasons?
Can wait
Can’t wait

8. IV. Life History Evolution Trade-Offs
5. Examples
- Suppose the probability of adult survival is low for other reasons? predation
High mortality selects for early, high reproduction

9. IV. Life History Evolution Trade-Offs
5. Examples
- Suppose the probability of adult survival is low for other reasons? predation
Populations of guppies in the presence of predators had:
- smaller male size
- More offspring
- smaller offspring size

10. IV. Life History Evolution Trade-Offs
5. Examples
- Suppose the probability of adult survival is low for other reasons? predation
11 years after a transplant experiment, those with predators had:
- smaller size
earlier reproduction
More offspring
Smaller offspring

11. B. Timing 1. First Age of Reproduction
- When all else is equal, reproducing early and often is adaptive; even if it kills you. The faster you create copies that can copy themselves, the more the "compounding interest" effect of exponential reproduction can get working for you.
Aphid "stem mother" produces live offspring asexually...

12. - But if that's true, why are there perennials?
Because environment matters. Lots of small offspring means that they only survive in a benign environment. But some environments are not benign... so the only way to reproduce successfully is to produce larger offspring... which may require longer survival to accumulate resources to make large offspring.

13. - But if that's true, why are there perennials?
Because environment matters. Lots of small offspring means that they only survive in a benign environment. But some environments are not benign... so the only way to reproduce successfully is to produce larger offspring... which may require longer survival to accumulate resources to make large offspring.
- Or, as a consequence of storing energy, you may be able to reproduce disproportionately more later and 'recoup' the losses of delaying reproduction. 1 2 3 4
Annual 10
100
10,000
1,000,000
Perennial
1,000,001 each year

14. 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

15. 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.

16. 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.
Back to opossums:
Mainland pop’s, with lower survivorship, had greater muscle deterioration (not benefit to repair).

17. III. Life History Evolution Trade-Offs Timing
Sex Determination and Sex Ratios
- Environmental
temperature

18. nutrients, energy availability
- environmental
temperature
nutrients, energy availability
Arisaema triphyllum
“Jack-in-the-Pulpit”
Small plants - male
Large plants - female

19. nutrients, energy availability social environment
- environmental
temperature
nutrients, energy availability
social environment
Sexually mature female
(Inhibits development of males)
Sexually mature male
Immature males
Wouldn’t the species do better if there were more females/group?
Yes, but selection favors individual reproductive success.

20. nutrients, energy availability social environment
- environmental
temperature
nutrients, energy availability
social environment
Sexually mature male
(Inhibits development of females)
Sexually mature female
Immature females

21. nutrients, energy availability social environment
- environmental
temperature
nutrients, energy availability
social environment
Midas cichlid
Brood

22. nutrients, energy availability social environment
- environmental
temperature
nutrients, energy availability
social environment
Midas cichlid
Add Larger juveniles
Brood
female

23. nutrients, energy availability social environment
- environmental
temperature
nutrients, energy availability
social environment
Midas cichlid
Add smaller juveniles
Brood
male

24. III. Life History Evolution Trade-Offs Timing
Sex Determination and Sex Ratios
1. Sex Determination
2. Adjusting Sex Ratio of Offspring
Small does and starving does selectively abort male embryos. Small daughters may still mate; small sons will not acquire a harem and will not mate. Selection has favored females who save their energy, abort male embryos when starving, and maybe live to reproduce next year.

25. IGFII gene – stimulates growth
C. Sex Determination and Sex Ratios
1. Sex Determination
2. Adjusting Sex Ratio of Offspring
3. Parent Conflicts
IGFII gene – stimulates growth
On in males, stimulating the growth of their own offspring; off in females, as she bears the cost of growing embryos and all are hers.

26. IGFII inhibitor gene – slows growth
C. Sex Determination and Sex Ratios
1. Sex Determination
2. Adjusting Sex Ratio of Offspring
3. Parent Conflicts
IGFII inhibitor gene – slows growth
Off in males, stimulating the growth of their own offspring; on in females, as she bears the cost of growing embryos and all are hers.

27. III. Life History Evolution Trade-Offs Timing
Sex Determination and Sex Ratios
D. Life History Strategies r
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