1. Life Histories (Ch. 12)

2. Life history trade-offs
Principle of Allocation: Energy used for one function unavailable for others
Leads to trade-offs (such as number vs. size offspring)
Exs……

3. Seed Size vs. Number in Plants
Plant life history variation
Ex, seed size vs. seed number

4. Seed Size vs. Number
Scatterhoarded larger (seed reward for dispersal), wind smaller (lightweight goes farther)
Dispersal mode influences seed size

5. Seed Size vs. Number Does plant growth form influence seed size?
Growth form: life history feature--body structure
Graminoids: Grass & grass-like plants.
grass
sedge
rush

6. Seed Size vs. Number
Forbs: Herbaceous (not woody), non-graminoids.

7. Seed Size vs. Number
Woody Plants: Woody thickening of tissues.

8. Seed Size vs. Number
Climbers: Climbing plants & vines.

9. Seed Size vs. Number
Woody plants + climbers produce larger seeds

10. Life history trade-offs
Principle of Allocation: Energy used for one function unavailable for others
Leads to trade-offs (such as number vs. size offspring)
Exs……

11. Life History Trade-offs
Vertebrates….

12. Life History Tradeoffs
Energy allocated to reproduction: reproductive effort
Energy budgets & sexual maturity.
Before maturity - maintenance or growth.
After maturity - maintenance, growth, or reproduction.
Trade-off:
Delay reproduction: grow faster & reach larger size
But reproducing early guarantees offspring…..

13. Life History Tradeoffs
Survival rate correlates positively with age at maturity

14. Life History: Vertebrate Species
Fish: adult mortality correlates negatively with age maturity

15. Life History: Vertebrate Species
Also, mortality correlates (+) with reproductive effort
(measured by GSI: ovary weight divided by body weight)

16. Life History Classification
Principle of Allocation: Energy used for one function unavailable for others
Leads to trade-offs (such as number vs. size offspring)
Classification systems:
1) r and K
2) CSR (plants)
3) Opportunistic, equilibrium, periodic (animals)
4) Life history cube (animals)

17. r and K system MacArthur and Wilson r and K ends of continuum
r selection (r: per capita rate of increase)
High population growth rate.
K selection (K: carrying capacity)
Efficient resource use.
r and K ends of continuum
E.O. Wilson

18. r and K system
Intrinsic Rate of Increase (rmax): Highest r selected species
Competitive Ability: Highest K selected species.
Reproduction:
r: Numerous individuals rapidly produced.
K: Fewer larger individuals slowly produced.
Know this Table!

19. r and K system semelparity: 1 reproductive event
iteroparity: repeated reproductive events
r selection: Unpredictable environments.
K selection: Predictable environments.

20. Plant Life Histories (CSR system)

21. Plant Life Histories Grime--2 important variables:
Intensity disturbance: Destroys biomass.
Intensity stress: Limits biomass production (drought, temperature, salt stress, etc).
Hurricane impact forest

22. Plant Life Histories 4 Environmental Extremes:
Low Disturb. : Low Stress
Low Disturb. : High Stress
High Disturb. : Low Stress
High Disturb. : High Stress
3 strategies

23. 3 Strategies Ruderals (high disturb. - low stress)
Grow rapidly, seed fast
Stress-Tolerant (low disturb. - high stress)
Grow slowly - conserve resources.
Competitive (low disturb. - low stress)
Compete for resources.
Last environmental category: high disturb. - high stress?

24. Plant Life Histories

25. Life History Classification
Principle of Allocation: Energy used for one function unavailable for others
Leads to trade-offs (such as number vs. size offspring)
Classification systems:
1) r and K
2) CSR (plants)
3) Opportunistic, equilibrium, periodic (animals)
4) Life history cube (animals)

26. Opportunistic, Equilibrium, and Periodic Life Histories
Winemiller and Rose--classification based on:
1) age of reproductive maturity ()
2) juvenile survivorship (lx)
3) fecundity (mx)
Strategies:
Opportunistic: low lx - low mx - early 
Equilibrium: high lx - low mx - late 
Periodic: low lx - high mx - late 

27. Opportunistic, Equilibrium, and Periodic Life Histories
Opportunistic: low lx - low mx - early 
Equilibrium: high lx - low mx - late 
Periodic: low lx - high mx - late 

28. Opportunistic, Equilibrium, and Periodic Life Histories
Same axes: fish most, mammals least variety

29. Reproductive Effort, Offspring Size, and Benefit-Cost Ratios
Charnov (life history cube)
Convert life history features to dimensionless numbers.
Remove influences time & size: reveals similarities/differences

30. Reproductive Effort, Offspring Size, and Benefit-Cost Ratios
1) Reproductive effort per unit of adult mortality (proportion body mass allocated to reproduction per unit time, divided by adult mortality rate)
scales reproductive effort to mortality cost

31. Reproductive Effort, Offspring Size, and Benefit-Cost Ratios
2) Relative reproductive lifespan (length reproductive life divided by time to maturity)

32. Reproductive Effort, Offspring Size, and Benefit-Cost Ratios
3) Relative offspring size (mass of offspring at independence, divided by adult mass)

33. Reproductive Effort, Offspring Size, and Benefit-Cost Ratios
Place organisms in “life history cube”
Fish, mammals, altricial birds (provide care for young) separate well