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 REPRODUCTION METABOLISM SURVIVAL REPRODUCTION

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

IV. Life History Evolution A.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: Evolution

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 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 5 th offspring is the same as the cost of the second.

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

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

METABOLISM REPRODUCTION METABOLISM REPRODUCTION 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

IV. Life History Evolution A.Trade-Offs 4. Trade-offs Between # offspring and offspring survival – Lack Hypothesis Again, diminishing returns, then net cost LaidFledgedDiff

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

- 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... B. Timing 1. First Age of Reproduction

- 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.

- 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 Annual ,0001,000,000 Perennial0001,000,001 each year

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; IF quantity can be increased disproportionately

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 Variable environment; “all in” when favorable may not get another chance Benign environment; no need to sacrifice future reproduction.

III. Life History Evolution A.Trade-Offs B.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.

III. Life History Evolution A.Trade-Offs B.Timing C.Life History Strategies r Unstable environment, density independent K Stable environment, density dependent interactions small size of organismlarge size of organism energy used to make each individual is lowenergy used to make each individual is high many offspring are producedfew offspring are produced early maturity late maturity, often after a prolonged period of parental care short life expectancylong 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

III. Life History Evolution A.Trade-Offs B.Timing C.Life History Strategies