Chap.13 Adaptation of Life Histories 鄭先祐 (Ayo) 國立台南大學 環境生態研究所

Adaptation of life histories 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 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 Concepts in life-history theory 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 Fitness –(p.312)

Adaptation of life histories 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 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 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 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 Growth and maturation The first major life-history problem an animal faces is when to start reproduction? 存活率 fecundity Age at maturity LRS ( 體積 ) Fig 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).

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

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

Adaptation of life histories 12 A = assimilation = aw b R = respiration = rw b w = body mass P = production = (a-r)w b C= a- r m = mortality = dP/dw

Adaptation of life histories 13 Fig 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 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 Production (a) plotted against body mass for 50 species in a resource allocation model Open circles m= c=0.015 Dots m= c=0.030 Trangles m= c=0.015

Adaptation of life histories 16 問題與討論