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Chapter 5 Life History Strategies. 生活史策略. © 2002 by Prentice Hall, Inc. Upper Saddle River, NJ 07458. Outline. Reproductive strategies Species that reproduce throughout their lifetimes (iteroparous 反覆 生殖 ) Species that reproduce just once (semelparous 單次生殖 ). Outline. Age structure

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chapter 5 life history strategies

Chapter 5Life History Strategies

生活史策略

© 2002 by Prentice Hall, Inc.

Upper Saddle River, NJ 07458

outline
Chapt. 05Outline
  • Reproductive strategies
    • Species that reproduce throughout their lifetimes (iteroparous反覆生殖)
    • Species that reproduce just once (semelparous單次生殖)
outline3
Chapt. 05Outline
  • Age structure
    • Growing populations
    • Declining populations
  • Classification of mating systems
outline4
Chapt. 05Outline
  • Continuum of life history strategies
    • r-selected
    • K-selected
    • Carrying capacity承載量
life history strategies fundamental aspects
Chapt. 05Life history strategiesFundamental aspects:

1.   Size體型:

2.   Metamorphosis變態;

3.   Diapause滯育;

4.   Senescence衰老;5.   Reproductive patterns繁殖模式;

life history strategies fundamental aspects6
Chapt. 05Life history strategiesFundamental aspects:

1.   Size體型:The mass and dimensions typical of adult individuals of a species.

2.   Metamorphosis變態;

3.   Diapause滯育;

4.   Senescence衰老;5.   Reproductive patterns繁殖模式;

the effects of body size
The effects of body size.

Chapt. 05

體型

體表面積

附肢

比例

食物、代謝、

運動能力

life history strategies fundamental aspects8
Chapt. 05Life history strategiesFundamental aspects:

1.   Size體型:

2.   Metamorphosis變態;The presence of a major developmental change in shape of form from the juvenile to the adult.

3.   Diapause滯育;

4.   Senescence衰老;5.   Reproductive patterns繁殖模式;

life history strategies fundamental aspects9
Chapt. 05Life history strategiesFundamental aspects:

1.   Size體型:

2.   Metamorphosis變態;

3.   Diapause滯育;The present of a resting stage in the life history.

4.   Senescence衰老;5.   Reproductive patterns繁殖模式;

life history strategies fundamental aspects10
Chapt. 05Life history strategiesFundamental aspects:

1.   Size體型:

2.   Metamorphosis變態;

3.   Diapause滯育;

4.   Senescence衰老;The process and timing of aging, degeneration, and death.5.   Reproductive patterns繁殖模式;

life history strategies fundamental aspects12
Chapt. 05Life history strategiesFundamental aspects:

1.   Size體型:

2.   Metamorphosis變態;

3.   Diapause滯育;

4.   Senescence衰老;5.   Reproductive patterns繁殖模式;The magnitude and timing of reproductive events (clutch size, age at reproductive maturity, size of young, number of reproductive events in a life time, amount of parental investment and care, and the like).

reproductive power is limited by two processes
Reproductive power is limited by two processes:

Chapt. 05

1. The acquisition of energy, which increases with mass raised to the 0.75power.

2. The rate of conversion of energy to offspring, which changes as a function of mass to the –0.25 power.

reproductive strategies
Chapt. 05Reproductive Strategies
  • Semelparity
    • Organisms that produce all of their offspring in a single reproductive event.
    • May live several years before reproducing or lifespan is one year (ex. Annual plants)
reproductive strategies15
Chapt. 05Reproductive Strategies
  • Semelparity (cont.).
    • Ex. Figure 5.1.
reproductive strategies16
Chapt. 05Reproductive Strategies
  • Iteroparity
    • Organisms that reproduce in successive years or breeding seasons
    • Variation in the number of clutches and number of offspring per clutch.
reproductive strategies17
Chapt. 05Reproductive Strategies
  • Iteroparity (cont.).
    • Some species have distinct breeding seasons
      • Ex. Temperate birds and temperate forest trees
      • Lead to distinct generations
reproductive strategies18
Chapt. 05Reproductive Strategies
  • Iteroparity (cont.).
    • Some species reproduce repeatedly and at any time during the year (continuous iteroparity)
      • Ex. Some tropical species, many parasites, and humans
reproductive strategies19
Chapt. 05Reproductive Strategies
  • Environmental Uncertainty
    • Favors iteroparity
    • Survival of juveniles is poor and unpredictable
    • Selection favors
      • Repeated reproduction
      • Long reproductive life
reproductive strategies20
Chapt. 05Reproductive Strategies
  • Environmental Uncertainty
      • Spread the risk over a longer period (“bet hedging”)
  • Environmental Stable
    • Favors semelparity
reproductive strategies21
Chapt. 05Reproductive Strategies
  • Environmental Stable (cont).
    • More energy can be devoted to seed production rather than maintenance
    • Annuals rely on seed storage during environmentally unstable years
slide22
洄游性鮭魚的產卵策略

Chapt. 05

陸封型鮭魚的產卵策略又如何?

age structure
Chapt. 05Age Structure
  • Semelparous organisms
    • Often produce groups of same-aged young – cohorts
    • Cohorts grow at similar rates
  • Iteroparous organisms
    • Many young at different ages
age structure24
Chapt. 05Age Structure
  • Increasing populations – large number of young
  • Decreasing populations – few young
    • Loss of age classes
      • Influence on population
age structure25
Chapt. 05Age Structure
  • Loss of age classes (cont.).
    • Ex. Overexploited fish populations – older age classes
      • Reproductive age classes removed
      • Reproductive failure
      • Results in population collapse
    • Ex. Younger age classes, deer removing young trees
      • Figure 5.2
slide26
Chapt. 05

60

(a) Age distribution in an

undisturbed forest

40

20

Percent of trees

(b) Age distribution skewed toward adults

where overgrazing has reduced the abundance

of young trees

60

40

20

10

20

30

40

50

60

70

Age (years)

mating systems
Chapt. 05Mating Systems
  • Sex ratio
    • Applied ecology
      • Hunters prefer deer populations dominated by males
      • Effects of too many males on population growth
    • Analysis of the ratio
mating systems28
Chapt. 05Mating Systems
  • Why is the sex ratio usually 1:1?
    • Aren’t males superfluous?
    • Answer: Selfish genes!
      • Populations – predominately female
      • Populations – predominately male
      • Over time, sex ratio would be kept at 1:1
  • Selection would favor sons
  • Selection would favor daughters
mating systems29
Chapt. 05Mating Systems
  • Exception to 1:1
    • One male dominates in breeding
    • Occurs in species with
      • Low powers of dispersal
      • Inbreeding is frequent
mating systems30
Chapt. 05Mating Systems
  • Ex. The parasitic Hymenoptera
    • Females mate once and store sperm
    • Females control sex ratio
      • Use sperm to create females
      • Without sperm to create males
    • Process termed haplodiploid
  • Ex. The mite Acarophenox (Figure 5.3)
mating systems31
Chapt. 05Mating Systems
  • Mating systems in animals
    • Monogamy
      • Exclusive mating
      • Common among birds (~90%) of species
mating systems32
Chapt. 05Mating Systems
  • Polygamy
    • Individuals mate with multiple partners
    • Polygyny
      • One male mates with multiple females
      • Females mate with one male
mating systems33
Chapt. 05Mating Systems
    • Polyandry
      • One female mates with multiple males
      • Males mate with one female
  • Polygyny
    • Females must care for the young
    • Mammals tend to be polygynous
      • Ex. Figure 5.4
mating systems34
Chapt. 05Mating Systems
  • Polygyny (cont.).
    • Influenced by spatial and temporal distribution of females
      • Monogamous relationships result from all females becoming sexually receptive at the same time
      • Female receptiveness spread over weeks or months – polygyny can result
mating systems35
Chapt. 05Mating Systems
  • Resource-based polygyny
    • Critical resource is patchily distributed or in short supply
    • Male can dominate resource and breed with more than one visiting female
    • Disadvantages for the female
      • Must share resources
      • More females means less success
      • Figure 5.5
slide36
Chapt. 05

5

1.25

4

1.0

3

Number of yearlings per male ( )

Number of yearlings per female ( )

0.75

2

0.5

1

1

2

3

4

5

6

Number of females per group

mating systems37
Chapt. 05Mating Systems
  • Non-resource based polygyny
    • Harem-based
      • Common in groups or herds
      • Protection from predators
      • Harem master does not remain for long
    • Communal courting areas – leks
      • Figure 5.6
mating systems38
Chapt. 05Mating Systems
  • Polyandry
    • Practiced by a few species of birds
    • Ex. Spotted sandpiper in the Arctic tundra
      • Reproductive success not limited by food
      • Limited by the number of males needed to incubate eggs.
    • Ex. American jacana (Figure 5.7)
life history strategies
Chapt. 05Life History Strategies
  • Success of populations
    • Reproductive strategies
    • Survival strategies
    • Habitat usage
    • Competition with other organisms
life history strategies40
Chapt. 05Life History Strategies
  • K-Selected
    • Populations increase slowly toward the carrying capacity
    • (K) of the environment
    • Low reproductive allocations
    • Iteroparous
    • High competitive abilities
life history strategies41
Chapt. 05Life History Strategies
  • Ex. Mature forest
    • Non-disturbed habitat
    • Grow slowly
    • Reach reproductive age late
    • Devote large amounts of energy to growth and maintenance
life history strategies42
Chapt. 05Life History Strategies
  • Ex. Mature forest (cont.).
    • Grow to large sizes and shade-out r-selected species
    • Long-lived and produce seeds repeatedly every year while mature
    • Seeds are bigger than r-selected species – provide food reserves to help them get started
life history strategies43
Chapt. 05Life History Strategies
  • Alternatives to the r and K continuum
    • Ruderals, competitors, and stress tolerators (Grime 1977 and 1979)
      • Ruderals (botanical term for weed)
        • Adapted to cope with habitat disturbances
life history strategies44
Chapt. 05Life History Strategies
  • Competitors
    • Adapted to live in highly competitive but benign environments (e.g., tropics)
  • Stress tolerators
    • Adapted to cope with severe environmental conditions (e.g., salt marsh plants)
life history strategies45
Chapt. 05Life History Strategies
  • Stress, disturbance and competition triangle
    • Figure 5.9
slide46
Chapt. 05

STRESS

TOLERATORS

COMPETITORS

RUDERALS

CHARACTERISTIC

Life form

Large herbs,

shrubs or trees

Lichens,

herbs,shrubs

Small herbs

Leaf size

  • Large
  • Small
  • Large
  • Short
  • Long

Life span

  • Long
  • Large

Seed production

  • Small
  • Small

Growth rate

  • Rapid
  • Rapid
  • Slow
  • Various
  • High
  • Low

Palatability

Vegetative spread

  • Yes
  • Yes
  • No

High

Low

Competitors

Leaf litter production

  • High
  • Low
  • Low

Disturbance

Competition

Intermediate

Life histories

Trees

Perennial

herbs

Annual

plants

Low

Lichens

High

Stress

tolerators

Ruderals

Bryophytes

High

Low

Stress

life history strategies47
Chapt. 05Life History Strategies
  • Demographic interpretation (Silverton et al. 1992, 1993)
    • Growth-survival and fecundity triangle
    • Figure 5.10
slide48
Chapt. 05

G

0.0

1.0

0.8

0.2

0.6

0.4

Survival

Growth

0.4

0.6

0.2

0.8

0.0

1.0

0.4

F

S

1.0

0.8

0.6

0.2

0.0

Fecundity

Semelparous herbs

Iteroparous herbs in open habitats

Iteroparous herbs in forests

Woody trees

applied ecology
Chapt. 05Applied Ecology
  • Life history and the risk of extinction
  • K-selected species
    • All attributes set them at risk to extinction
    • Tend to be bigger – need bigger habitat
applied ecology50
Chapt. 05Applied Ecology
  • K-selected species (cont.).
    • Fewer offspring – populations can not recover as fast from disturbance
    • Breed later in life – generation time is long
applied ecology51
Chapt. 05Applied Ecology
  • K-selected species (cont.).
    • Population size is small – high risk of inbreeding
    • Examples
      • Florida panthers
      • Giant sequoia tree
applied ecology52
Chapt. 05Applied Ecology
  • Examples (cont.).
    • Large terrestrial mammals (elephants, rhinoceros, and grizzlies)
    • Large marine mammals (blue and sperm whales)
summary
Chapt. 05 Summary
  • Life history concerns lifetime patterns in reproduction and growth patterns
    • Semelparous
    • Iteroparous
summary54
Chapt. 05 Summary
  • Reproductive strategy strongly affects age structure
    • Low ratio of young to adults – population in decline
    • High ratio of young to adults – population growing
summary55
Chapt. 05 Summary
  • Sex ratio
    • 1:1 ratio expected in most populations
    • Polygynous
      • Males mate with more than one female
summary56
Chapt. 05 Summary
  • Sex ratio
    • Polyandrous
      • Females mate with more than one male
      • Monogamous
        • Each individual has one mate
summary57
Chapt. 05 Summary
    • Polygamy is often based on limited resources
  • Categorizing life history strategies
    • r-K continuum
      • r-selected
        • Poor competitors
summary58
Chapt. 05 Summary
    • r-selected (cont.).
      • High per capita population growth rate
      • Disperse well
      • Colonize new habitats
    • K-Selected
      • Good competitors
      • Usually exist in mature habitats, close to the carrying capacity
  • Alternative life history strategies
summary59
Chapt. 05Summary
  • Alternative life history strategies
    • Ruderals, competitors, and stress tolerators classification
    • Growth-longevity-fecundity triangle
discussion question 1
Chapt. 05Discussion Question #1
  • What particular life history strategies are possessed by successful exotic invaders like kudzu in the southeast or zebra mussels in the Great Lakes? Can knowing their life histories help us in the war against exotics?
discussion question 2
Chapt. 05Discussion Question #2
  • How could you test the idea that there is a trade-off between life history strategies? What would happen if you plant salt marsh plants like Spartina grass or mangroves in a terrestrial habitat vs. a freshwater habitat?
discussion question 3
Chapt. 05Discussion Question #3
  • In some species, males are much bigger than females, a property called sexual dimorphism. Speculate about the types of animals in which sexual dimorphism would and would not occur.