IV. Life History Evolution
A. Trade-Offs
1.
Components of fitness?
- probability of survival
- number of offspring
- probability that offspring survive
IV. Life History Evolution
A. Trade-Offs
2. Relationships with Energy Budgets
GROWTH
METABOLISM
SURVIVAL
METABOLISM
REPRODUCTION
REPRODUCTION
IV. Life History Evolution
A. Trade-Offs
3. Trade-offs Between Survival and Reproduction
Maximize probability of survival
Maximize reproduction
GROWTH
GROWTH
METABOLISM
REPRODUCTION
METABOLISM
REPRODUCTION
IV. Life History Evolution
A. Trade-Offs
3. Trade-offs Between Survival and Reproduction
European Kestrels
IV. Life History Evolution
A. Trade-Offs
3. Trade-offs Between Survival and Reproduction
Cox, R.M., and R. Calsbeek. 2010. Severe costs of reproduction persist in Anolis lizards
despite the evolution of a single-egg clutch. Evolution 64: 1321-1330.
IV. Life History Evolution
A. Trade-Offs
3. Trade-offs Between Survival and Reproduction
IV. Life History Evolution
A. 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
Selection favors high fecundity in “fish” living less than four years, but low fecundity
for fish living more than four years
IV. Life History Evolution
A. 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
IV. Life History Evolution
A. Trade-Offs
4. Trade-offs Between # offspring and offspring survival
REPRODUCTION
METABOLISM
REPRODUCTION
METABOLISM
Lots of small, low prob
of survival
A few large, high prob
of survival
IV. Life History Evolution
A. Trade-Offs
4. Trade-offs Between # offspring and offspring survival – Lack Hypothesis
Again, diminishing returns
IV. Life History Evolution
A. Trade-Offs
4. Trade-offs Between # offspring and offspring survival – Lack Hypothesis
Varies within a species under different environmental conditions:
Guppies
IV. Life History Evolution
A. Trade-Offs
B. Timing
1. First Age of Reproduction
As lifespan increases, selection favors a delayed first age or reproduction
IV. Life History Evolution
A. Trade-Offs
B. Timing
1. First Age of Reproduction
2. Parity: How Often to Reproduce
- Semelparous vs. iteroparous
Semelparity = once
Iteroparity = iterative… many
IV. Life History Evolution
A. Trade-Offs
B. Timing
1. First Age of Reproduction
2. Parity: How Often to Reproduce
- Semelparous vs. iteroparous
III. Life History Evolution
A. Trade-Offs
B. Timing
1. First Age of Reproduction
2. Parity: How Often to Reproduce
3. Senescence
Why do human have a long postreproductive period?
The ‘grandmother effect’
Lahdenpera et al., 2005. Nature.
III. Life History Evolution
A. Trade-Offs
B. Timing
C. Life History Strategies
III. Sex and Selection
A. Costs and Benefits
1. Asexual
- major benefit of asexual: maximizes transfer of genes to next generation, and
maximizes survivorship in a constant environment
- major costs of asexual: “all or none” survivorship in changing environment, and
“Muller’s Ratchet”
2. Sexual:
- major cost: only ½ genes to each offspring
- major benefit: extraordinary production of variation; sexual lineages are more likely to
survive over time in changing environments.
III. Sex and Selection
A. Costs and Benefits
B. Sexual Selection
1. Mating Systems:
- should you have many mates
or one mate?
The polygamy threshold:
If resources are limiting and
patchy, a resident on a high
quality territory may provide
more resources to TWO mates
than a resident on a low quality
territory could provide to ONE
mate.
Selection may favor polygamy
(unless both parents are needed
to raise offspring).
III. Sex and Selection
A. Costs and Benefits (notes)
B. Sexual Selection
- selective pressures may differ between the sexes, resulting in selection for
different physiologies, morphologies, and behaviors.
1. Mating Systems:
- Polygyny or polyandry? Which sex has multiple mates?
The sex that invests more energy
in reproduction should be
choosey (monogamous)
NEWTS
# offspring
male
Jones (2002)
female
# mates
III. Sex and Selection
A. Costs and Benefits (notes)
B. Sexual Selection
- selective pressures may differ between the sexes, resulting in selection for
different physiologies, morphologies, and behaviors.
1. Mating Systems:
- Polygyny or polyandry? Which sex has multiple mates?
PIPEFISH
# offspring
female
Jones (2002)
male
# mates
III. Sex and Selection
A. Costs and Benefits (notes)
B. Sexual Selection
- selective pressures may differ between the sexes, resulting in selection for
different physiologies, morphologies, and behaviors.
1. Mating Systems:
2. Intrasexual Selection – where competition within a sex occurs
Sexual Selection
2. INTRAsexual Competition
- competition for harems, territories
Sexual Selection
2. INTRAsexual Competition
- competition for harems, territories
- sperm competition
Sexual Selection
2. INTRAsexual Competition
- competition for harems, territories
- sperm competition
- infanticide
Sexual Selection
2. INTRAsexual Competition
- competition for harems, territories
- sperm competition
- infanticide
- female mimicry in male subadults and "stealth matings"
"sneaker males"
FEMALE
"Sneaker" male
Sexual Selection
3. INTERsexual Selection (Mate Preference)
- A behavior or morphology that is only performed during the
reproductive season, which increases risk and must then be offset by mating
Sexual Selection
3. INTERsexual Selection (Mate Preference)
- A behavior or morphology that is only performed during the
reproductive season, which increases risk and must then be offset by mating
showy breeding plumage
calling displays
3. INTERsexual Selection (Mate Preference)
- WHY is it ADAPTIVE for the FEMALE to choose a given male??
1. Direct Benefit
- parental care
3. INTERsexual Selection (Mate Preference)
- WHY is it ADAPTIVE for the FEMALE to choose a given male??
1. Direct Benefit
- nuptual gifts (energy for egg making)
3. INTERsexual Selection (Mate Preference)
- WHY is it ADAPTIVE for the FEMALE to choose a given male??
1. Direct Benefit
2. Indirect Benefit: Good Genes
- ‘Handicap Theory’
3. INTERsexual Selection (Mate Preference)
- WHY is it ADAPTIVE for the FEMALE to choose a given male??
1. Direct Benefit
2. Indirect Benefit: Good Genes
- ‘Parasite Load Theory’
3. INTERsexual Selection (Mate Preference)
- WHY is it ADAPTIVE for the FEMALE to choose a given male??
1. Direct Benefit
2. Indirect Benefit: Good Genes
- ‘Symmetry Theory’
Hmmm....
3. INTERsexual Selection (Mate Preference)
- WHY is it ADAPTIVE for the FEMALE to choose a given male??
1. Direct Benefit
2. Indirect Benefit: Good Genes
- ‘Symmetry theory’
Hmmm....
3. INTERsexual Selection (Mate Preference)
- WHY is it ADAPTIVE for the FEMALE to choose a given male??
1. Direct Benefit
2. Indirect Benefit: Good Genes
- ‘Symmetry Theory’
Hmmm....
Hey, It Works!!
3. INTERsexual Selection (Mate Preference)
- WHY is it ADAPTIVE for the FEMALE to choose a given male??
1. Direct Benefit
2. Indirect Benefit: Good Genes
3. Runaway Selection