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IV. Life History Evolution Trade-Offs Components of fitness? - probability of survival

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.

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IV. Life History Evolution Trade-Offs Components of fitness? - probability of survival

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

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

  3. 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

  4. 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

  5. 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.

  6. 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.

  7. 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

  8. 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

  9. 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

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

  11. 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

  12. 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

  13. 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

  14. 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.

  15. 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)

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

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

  18. 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.

  19. 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).

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

  21. Selection for earlier age of maturity, too.

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