Chap.13 Adaptation of Life Histories

Chap.13 Adaptation of Life Chap.13 Adaptation of Life HistoriesHistories

鄭先祐鄭先祐靜宜大學生態學系教授靜宜大學生態學系教授

Adaptation of life historiesAdaptation of life histories 22

Adaptation of Life HistoriesAdaptation of Life Histories

13.1 Introduction13.1 Introduction

13.2 Concepts in life-history theory13.2 Concepts in life-history theory

13.3 Growth and maturation13.3 Growth and maturation

13.4 Scaling of time and energy13.4 Scaling of time and energy

13.5 Parental effort and investment13.5 Parental effort and investment

13.6 Seasonal timing13.6 Seasonal timing

13.7 Offspring size and numbers13.7 Offspring size and numbers

13.8 Population heterogeneity in life histories13.8 Population heterogeneity in life histories


13.1 Introduction13.1 Introduction

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


13.2 Concepts in life-history theory13.2 Concepts in life-history theory

13.2.1 Traits13.2.1 Traits– A trait is any quantitative property of a living A trait is any quantitative property of a living

organism. organism. – Life history concentrates on traits such as age Life history concentrates on traits such as age

of first reproduction, clutch size and sex ratio of first reproduction, clutch size and sex ratio of the offspring.of the offspring.

13.2.2 Fitness 13.2.2 Fitness – (p.312)(p.312)


13.2.3 Trade-offs13.2.3 Trade-offs– Since fitness is a complex measure, based on Since fitness is a complex measure, based on

multiple components, a change in strategy multiple components, a change in strategy may have negative consequences for one may have negative consequences for one component, and positive effects on another.component, and positive effects on another.

– Such consequences determine a trade-off, Such consequences determine a trade-off, e.g. between current and future reproduction, e.g. between current and future reproduction, or between the number of offspring and their or between the number of offspring and their reproductive value.reproductive value.


13.2.4 Optimization13.2.4 Optimization– By identifying trade-offs, we may hope to By identifying trade-offs, we may hope to

define models predicting optimal values for define models predicting optimal values for particular life-history traits; optimal at least particular life-history traits; optimal at least under particular conditions.under particular conditions.

– These values are those which maximize These values are those which maximize fitness.fitness.


13.2.5 Decision rules and reaction norms13.2.5 Decision rules and reaction norms– A reaction norm describes the variation in trait A reaction norm describes the variation in trait

values as a function of environment and/or values as a function of environment and/or condition.condition.

– Decision rules refer to the mechanism of Decision rules refer to the mechanism of response to these conditions.response to these conditions.

– In essence the two concepts are the same.In essence the two concepts are the same.– Reaction norms or decision rules are optimal Reaction norms or decision rules are optimal

if they maximize fitness for each if they maximize fitness for each environmental condition.environmental condition.


13.2.6 Constraints13.2.6 Constraints– We use the word constraints in the sense of the We use the word constraints in the sense of the

boundaries of the option set or parameter space.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.


13.3 Growth and maturation13.3 Growth and maturationThe first major life-history problem an animal The first major life-history problem an animal faces is when to start reproduction?faces is when to start reproduction?

存活率

fecundity

Age at maturity

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).


Fig13.3 Body mass as a function of age in female Arctic ChFig13.3 Body mass as a function of age in female Arctic Charr in Labrador.arr in Labrador.


13.4 Scaling of time and energy13.4 Scaling of time and energy

Body mass Body mass 的大小限制的大小限制時間與空間的使用。時間與空間的使用。Fig. 13.4 Allometry of thFig. 13.4 Allometry of the rate of living.e rate of living.


A = assimilation = awA = assimilation = awbb

R = respiration = rwR = respiration = rwbb

w = body massw = body mass

P = production = (a-r)wP = production = (a-r)wbb

C= a- rC= a- r

m = mortality = dP/dwm = mortality = dP/dw


Fig. 13.5 Production (a) plotted against body mass Fig. 13.5 Production (a) plotted against body mass for 50 species in a resource allocation modelfor 50 species in a resource allocation model

Squares = c constant, m varying

Dots = c varying, m constant

Circles = c varying, m varying


Fig. 13.5 age of maturity plotted against body mass for 50 Fig. 13.5 age of maturity plotted against body mass for 50 species in a resource allocation model.species in a resource allocation model.

Squares = c constant, m varying

Dots = c varying, m constant

Circles = c varying, m varying


Fig. 13.6 Production (a) plotted against body mass Fig. 13.6 Production (a) plotted against body mass for 50 species in a resource allocation modelfor 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

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Chap.13 Adaptation of Life Histories