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

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

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

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

IV. Life History Evolution Trade-Offs 5. Examples

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

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

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

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

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

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...

- 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. 1 2 3 4 Annual 10 100 10,000 1,000,000 Perennial 1,000,001 each year

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

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.

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).

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

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

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.

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

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

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

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

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.

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.

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.

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