Life History Strategy ?????

1
Life History Strategy?????

• Strategy 1. skill managing any affair
• 2. the art of planning
  operations
• in war
• Life history An individuals pattern of
  allocation, throughout life, of time and energy
  to various fundamental activities, such as
  growth, repair of cell and tissue damage, and
  reproduction

2
What is life history????

• The life history is the schedule of an organisms
  life and key to survival tactis, including

3
What influences life histories?????????

• Life histories are influenced by
• body plan and life style of the organism
• evolutionary responses to many factors,
  including
• physical conditions????
• food supply??
• predators??
• other biotic factors, such as competition????

4
Study of the Evolution of Life Histories

• The first is concerned with individual life
  history traits.
• The second is concerned with links between life
  history traits.
• The third is concerned with links between life
  histories and habitats
• search for pattern and for explanations for those
  patterns

5
C
A
B



X
X




A ??? 2/4 3/4 0 B ??? 4/2
2/3 0 ???AB2/44/21
3/42/30.5 0
Fitness
6
Fitness(???) Life History

• Fitness is ultimately dependent on producing
  successful offspring, so many life history
  attributes relate to reproduction
• maturity (age at first reproduction)??
• parity (number of reproductive episodes)????
• fecundity (number of offspring per reproductive
  episode)???
• aging (total length of life)??
• Reproductive values

7
Energy Costs and Benefits

• Zach determined that the optimal flight height in
  foraging behavior
• Correlated with a fewer number of drops,
  indicating a trade-off between energy gained
  (food) and energy expended

8
Energy allocation Trade-Offs

• Organisms face a problem of allocation of scarce
  resources (time, energy, materials)
• the trade-off resources used for one function
  cannot be used for another function

9

• If patchy habitat, those individuals that live on
  a poorer patch may need a larger area to obtain
  all necessary resourcesreach ideal free
  distributiontrade-off between poor habitat
  quality and reduced competition in marginal
  habitat

10
??????????
Fitness
a
c
b
11
Life histories balance trade offs.

• Principle of Allocation If organisms use energy
  for one function such as growth, the amount of
  energy available for other functions is reduced.
• Issues concerning life histories may be phrased
  in terms of three questions
• how many offspring should an individual produce
  in each breeding episode?
• when should an individual begin to produce
  offspring?
• how often should an individual breed?

12
Offspring Number Versus Size??????

• Leads to trade-offs between functions such as
  number and size of offspring.

13
(No Transcript)
14
Egg Size and Number in Fish

• Fish show more variation in life-history than any
  other group of animals.
• Turner and Trexter found darter populations that
  produce many small eggs showed less difference in
  allelic frequencies than populations producing
  fewer, larger eggs.
• Proposed larvae from larger eggs hatch earlier,
  feed earlier, do not drift as far, and thus do
  not disperse great distances.
• Greater isolation leads to rapid gene
  differentiation.

15
Seed Size and Number in Plants

• Many families produce small number of larger
  seeds.
• Dispersal mode might influence seed size.

16
Seed Size and Number in Plants

• Westoby et.al. recognized six seed dispersal
  strategies
• Unassisted No specialized structures.
• Adhesion Hooks, spines, or barbs.
• Wind Wings, hair, (resistance structures).
• Ant Oil surface coating (elaisome).
• Vertebrate Fleshy coating (aril).
• Scatter hoarded Gathered,stored in caches.

17
Seed Size and Number in Plants

• Small plants producing large number of small
  seeds appear to have an advantage in areas of
  high disturbance.
• Plants producing large seeds are constrained to
  producing fewer seedlings more capable of
  surviving environmental hazards.

18
Seed Size and Number in Plants

• Jakobsson and Eriksson found seed size variation
  explained many differences in recruitment
  success.
• Larger seeds produce larger seedlings and were
  associated with increased recruitment.

19
Life History Variation

• Shine and Charnov pointed out vertebrate energy
  budgets are different before and after sexual
  maturity.
• Before - maintenance or growth.
• After - maintenance, growth, or reproduction.
• Individuals delaying reproduction will grow
  faster and reach a larger size.
• Increased reproduction rate.

20
Age at First Reproduction?????????

• At each age, the organism chooses between
  breeding and not breeding.
• The choice to breed carries benefits
• increase in fecundity at that age
• The choice to breed carries costs
• reduced survival
• reduced fecundity at later ages

21
?????? ????
Species with higher mortality show higher
relative reproductive rate.
22
Figure 10.14
23
Adult Survival Rate

• Findings supported theory that when adult
  survival is lower relative to juvenile survival,
  natural selection will favor allocating greater
  resources to reproduction.

24
Figure 10.12
????????
25
Reproductive Effort

• Semelparous organisms?????
• Often produce groups of same-aged young cohorts
• Cohorts grow at similar rates
• Iteroparous organisms?????
• Many young at different ages

26

• Consider the following remarkable differences in
  life history between two species of similar size
• thrushes
• reproduce when 1 year old
• produce several broods of 3-4 young per year
• rarely live beyond 3 or 4 years
• petrels
• do not reproduce until they are 4 to 5 years old
• produce at most a single young per year
• may live to be 30 to 40 years old

27
(No Transcript)
28
(No Transcript)
29
For a Individual?
30
(No Transcript)
31
(No Transcript)
32
Energy Budgets, Beans Free of and under Beetle
Attack

• Life history strategies evolve under different
  environmental demands. This can be
  diagrammatically re presented with alternative
  energy budget allocations. The size of the arrow
  represents the size of th e energy investment.
  (a)Free of beetle attack, beans allocate more to
  Toxins and Growth than to Reproduction. (b)Under
  beetle attack, beans evolved a strategy of
  increased Reproduction, overwhelming beetles with
  a large output of seeds, but at the expense of
  Toxin production and vegetative Growth.

33
Mating Systems

• Monogamy ????
• Exclusive mating
• Common among birds (90) of species(before1980)
• Polygamy????
• Individuals mate with multiple partners
• Polygyny????
• One male mates with multiple females
• Females mate with one male
• Females must care for the young
• Mammals tend to be polygynous
• Polyandry????
• One female mates with multiple males
• Males mate with one female

34
Types of Polygyny

• 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
• 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

35
?????? ??????
36
(No Transcript)
37
????????????
38
?????????

• Rejected by DNA fingerprinting
• Few species, How evolved?
• Good wife hypothesis of monogamy
• Danger hypo.
• Mutually Assured Destruction hypo.

39
????
40
Senescence is a decline in function with age??

• Senescence is an inevitable decline in
  physiological function with age.
• Many functions deteriorate
• most physiological indicators (e.g., nerve
  conduction, kidney function)
• immune system and other repair mechanisms
• Other processes lead to greater mortality
• incidence of tumors and cardiovascular disease

41
Figure 10.18
42

• Not all organisms senescence at the same rate,
  suggesting that aging may be subject to natural
  selection
• organisms with inherently shorter life spans may
  experience weaker selection for mechanisms that
  prolong life
• repair and maintenance are costly investment in
  these processes reduces investment in current
  fecundity

??????
43
??????????

• ?????
• ?????
• ?????
• ????????
• ????
• ????
• ???Jared Diamond Why is sex fun?
• (???????? ???? 1998)

44
Life History Variation Intraspecific Level
45
Figure 10.6
46
Lizards
47
An Experiment with Tadpoles

• Tadpoles fed different diets illustrate the
  complex relationship between size and age at
  metamorphosis
• individuals with limited food tend to
  metamorphose at a smaller size and later age than
  those with adequate food (compromise solution)
• ????????????

48
Figure 10.11
49
(No Transcript)
50
Male guppies, friends and foes

• Guppies (Poecilia reticulata) occupy pools
  separated by waterfalls. In pools where
  predators, such as the pike cichlid (Crenicichla
  altra), are present, males are drab. Where
  predators are absent, male guppies are brightly
  colored and attract females.
• ???????

51
(No Transcript)
52
Guppies
53
Rock Pipit
54
Dilemma of Prisoners

• Game theory evaluates alternative behavioral
  strategies in situations
• Where the outcome depends on each individuals
  strategy and the strategy of other individuals

55
(No Transcript)
56
What influences life histories and Can predict
them?

• Life histories are influenced by
• body plan and life style of the organism
• size determines lifestyle
• Shape reveals function
• Examples
• Teeth
• Stomach
• Successive adaptations over long periods of time

57
(No Transcript)
58
(No Transcript)
59
Form Follows Function
60
Locomotion and Shape

• Swimmer Adaptations
• Streamlined shape
• Tail broad and flat
• Undulate through water
• Examples seals, fish, snakes

61
Flying Adaptations

• Powerful wings
• Light skeleton
• Hollow bones
• Reduced jaws and legs
• Reproductive structures that shrink
• Streamlined digestive tracts

62
Running Adaptations

• Increased stride length
• Increased stride rate
• Long legs
• Specialized shoulders
• Flexible spine

63
(No Transcript)
64
(No Transcript)
65
Temp. gt20C Humidity gt 75
66
Size and Metabolic Rate

• Size influences metabolic rate
• Small warm-blooded animals have greater metabolic
  rates
• Small animals use more calories per gram of body
  weight
• Small animals use more oxygen per gram of body
  weight

67
(No Transcript)
68
Weight-specific BMR as a function of body weight
in various species
69
Weight-specific metabolic rate as a function of
body weight in four groups of vertebrates
70
Expanding Surface Areas

• Some body parts expand their surface areas
• Webbed feet
• Intestines
• Circulatory system
• Large ears

71
(No Transcript)
72
(No Transcript)
73
????
74
(No Transcript)
75
Intrinsic Rates of Increase?????

• On average, small organisms have higher rates of
  per capita increase and more variable populations
  than large organisms.

76
(No Transcript)
77
(No Transcript)
78
The Slow-Fast Continuum???????

• Life histories vary widely among different
  species and among populations of the same
  species.
• Several generalizations emerge
• life history traits often vary consistently with
  respect to habitat or environmental conditions
• variation in one life history trait is often
  correlated with variation in another

79
The Slow-Fast Continuum

• Life history traits are generally organized along
  a continuum of values
• at the slow end of the continuum are organisms
  (such as elephants, giant tortoises, and oak
  trees) with
• long life
• slow development
• delayed maturity
• high parental investment
• low reproductive rates
• at the fast end of the continuum are organisms
  with the opposite traits (mice, fruit flies,
  weedy plants)

80
Life History Classification

• MacArthur and Wilson
• r selection (per capita rate of increase)
• Characteristic high population growth rate.
• K selection (carrying capacity)
• Characteristic efficient resource use.
• Pianka r and K are ends of a continuum, while
  most organisms are in-between.
• r selection Unpredictable environments.
• K selection Predictable environments.

81
(No Transcript)
82
r and K Fundamental Contrasts

• Intrinsic Rate of Increase
• Highest in r selected species.
• Competitive Ability
• Highest in K selected species.
• Reproduction
• r Numerous individuals rapidly produced.
• K Fewer larger individuals slowly produced.

83
Plant Life Histories

• Grime proposed two most important variables
  exerting selective pressures in plants
• Intensity of disturbance
• Any process limiting plants by destroying
  biomass.
• Intensity of stress
• External constraints limiting rate of dry matter
  production.

84
Plant Life Histories

• Four Environmental Extremes
• Low Disturbance Low Stress
• Low Disturbance High Stress
• High Disturbance Low Stress
• High Disturbance High Stress

85
Plant Life Histories

• Ruderals (highly disturbed habitats)
• Grow rapidly and produce seeds quickly.
• Stress-Tolerant (high stress - no disturbance)
• Grow slowly - conserve resources.
• Competitive (low disturbance low stress)
• Grow well, but eventually compete with others for
  resources.

86
Plant Life Histories
87
Opportunistic, Equilibrium,and Periodic Life
Histories

• Winemiller and Rose proposed new classification
  scheme based on age of reproductive maturity (?),
  juvenile survivorship (lx) and fecundity (mx).
• Opportunistic low lx - low mx - early ?
• Equilibrium high lx - low mx - late ?
• Periodic low lx - high mx - late ?

88
Opportunistic, Equilibrium,and Periodic Life
Histories
89
Reproductive Effort, Offspring Size, and
Benefit-Cost Ratios

• Charnov developed a new approach to life history
  classification.
• Took a few key life history features and
  converted them to dimensionless numbers.
• By removing the influences of time and size,
  similarities and differences between groups are
  easier to identify.

90
Reproductive Effort, Offspring Size, and
Benefit-Cost Ratios