Chap.13 Adaptation of Life Histories

1. Chap.13 Adaptation of Life Histories 鄭先祐 靜宜大學 生態學系 教授

2. Adaptation of Life Histories • 13.1 Introduction • 13.2 Concepts in life-history theory • 13.3 Growth and maturation • 13.4 Scaling of time and energy • 13.5 Parental effort and investment • 13.6 Seasonal timing • 13.7 Offspring size and numbers • 13.8 Population heterogeneity in life histories Adaptation of life histories

3. 13.1 Introduction • Life history is the distribution of major events over the lifetime of individuals. • Life history studies concern the timing and the intensity of reproduction, as well as the processes generating this temporal distribution. • They analyze life span, age and size at maturity, the trade-offs between somatic growth, maintenance and repair versus reproduction, the decisions on number and size of the offspring, the investment in current offspring and in future reproductive attempts. Adaptation of life histories

4. 13.2 Concepts in life-history theory • 13.2.1 Traits • A trait is any quantitative property of a living organism. • Life history concentrates on traits such as age of first reproduction, clutch size and sex ratio of the offspring. • 13.2.2 Fitness • (p.312) Adaptation of life histories

5. 13.2.3 Trade-offs • Since fitness is a complex measure, based on multiple components, a change in strategy may have negative consequences for one component, and positive effects on another. • Such consequences determine a trade-off, e.g. between current and future reproduction, or between the number of offspring and their reproductive value. Adaptation of life histories

6. 13.2.4 Optimization • By identifying trade-offs, we may hope to define models predicting optimal values for particular life-history traits; optimal at least under particular conditions. • These values are those which maximize fitness. Adaptation of life histories

7. 13.2.5 Decision rules and reaction norms • A reaction norm describes the variation in trait values as a function of environment and/or condition. • Decision rules refer to the mechanism of response to these conditions. • In essence the two concepts are the same. • Reaction norms or decision rules are optimal if they maximize fitness for each environmental condition. Adaptation of life histories

8. 13.2.6 Constraints • We use the word constraints in the sense of the boundaries of the option set or parameter space. Fig 13.1 The dashed line is the optimal reaction norm connecting the optima for different environments. Adaptation of life histories

9. 13.3 Growth and maturation • The first major life-history problem an animal faces is when to start reproduction? LRS (體積) Fig. 13.2 Optimization of age and size at maturity in Kozlowski’s model. The switch from growth to reproduction at age a2 yields a higher lifetime reproduction success (LRS). fecundity 存活率 Age at maturity Adaptation of life histories

10. Fig13.3 Body mass as a function of age in female Arctic Charr in Labrador. Adaptation of life histories

11. 13.4 Scaling of time and energy • Body mass 的大小限制時間與空間的使用。 • Fig. 13.4 Allometry of the rate of living. Adaptation of life histories

12. A = assimilation = awb • R = respiration = rwb • w = body mass • P = production = (a-r)wb • C= a- r • m = mortality = dP/dw Adaptation of life histories

13. Fig. 13.5 Production (a) plotted against body mass for 50 species in a resource allocation model Squares = c constant, m varying Dots = c varying, m constant Circles = c varying, m varying Adaptation of life histories

14. Fig. 13.5 age of maturity plotted against body mass for 50 species in a resource allocation model. Squares = c constant, m varying Dots = c varying, m constant Circles = c varying, m varying Adaptation of life histories

15. Fig. 13.6 Production (a) plotted against body mass for 50 species in a resource allocation model Open circles m=0.0002 c=0.015 Dots m=0.0002 c=0.030 Trangles m=0.0004 c=0.015 Adaptation of life histories