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 3. Trade-offs Between Survival and Reproduction Add 2 chicks. Fledge an additional 0.75 chicks, at a cost of 10% decrease in survivorship European Kestrels

IV. Life History Evolution 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 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 5th offspring is the same as the cost of the second.

IV. Life History Evolution 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 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 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 4. Trade-offs Between # offspring and offspring survival Decrease size, decrease probability of survival

IV. Life History Evolution Trade-Offs 4. Trade-offs Between # offspring and offspring survival – Lack Hypothesis Decrease size through decreased parental care, decrease survival Again, diminishing returns, then net cost Laid Fledged Diff. 5 2.25 6 3 0.75 7 3.5 0.50 8 -1.25

IV. Life History Evolution 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 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. Why do human have a long post-reproductive period? The ‘grandmother effect’ Lahdenpera et al., 2005. Nature. Finland, 1702–1823, (6,002 grandchildren born). Canada, 1850 to 1879 ,(100,074 grandchildren born)

III. Life History Evolution Trade-Offs Timing Life History Strategies 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

III. Life History Evolution Trade-Offs Timing Life History Strategies

III. Life History Evolution Trade-Offs Timing Life History Strategies Effects of Humans Tree swallows breed 9 days earlier in North America; salamanders in Britain bred 7 weeks earlier! Correlates with mean temperature.

III. Life History Evolution Trade-Offs Timing Life History Strategies Effects of Humans Flowerin gof 42 plants in Concord, MA, is an average of 7 days earlier than when recorded by Thoreau in 1852, and mean temp is 2.4oC higher (~ 4oF).

III. Life History Evolution Trade-Offs Timing Life History Strategies Effects of Humans

Selection for earlier age of maturity, too.