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The Evolution of Cooperation
The Evolution of Cooperation
I. Issue
- How can cooperation evolve, especially if by cooperating, an entity
reduces its own immediate fitness in sacrifice to that of another?
The Evolution of Cooperation
I. Issue
- How can cooperation evolve, especially if by cooperating, an entity
reduces its own immediate fitness in sacrifice to that of another?
- However, cooperation is OBSERVED and necessary:
The Evolution of Cooperation
I. Issue
- How can cooperation evolve, especially if by cooperating, an entity
reduces its own immediate fitness in sacrifice to that of another?
- However, cooperation is OBSERVED and necessary:
among genes in a genome
The Evolution of Cooperation
I. Issue
- How can cooperation evolve, especially if by cooperating, an entity
reduces its own immediate fitness in sacrifice to that of another?
- However, cooperation is OBSERVED and necessary:
among genes in a genome
among organelles in a cell
The Evolution of Cooperation
I. Issue
- How can cooperation evolve, especially if by cooperating, an entity
reduces its own immediate fitness in sacrifice to that of another?
- However, cooperation is OBSERVED and necessary:
among genes in a genome
among organelles in a cell
among cells in a multicellular organism
The Evolution of Cooperation
I. Issue
- How can cooperation evolve, especially if by cooperating, an entity
reduces its own immediate fitness in sacrifice to that of another?
- However, cooperation is OBSERVED and necessary:
among genes in a genome
among organelles in a cell
among cells in a multicellular organism
among organisms in a social group
The Evolution of Cooperation
I. Issue
- How can cooperation evolve, especially if by cooperating, an entity
reduces its own immediate fitness in sacrifice to that of another?
- However, cooperation is OBSERVED and necessary:
among genes in a genome
among organelles in a cell
among cells in a multicellular organism
among organisms in a social group
between species in symbiotic relationships
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
A. Kin Selection (W. D. Hamilton)
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
A. Kin Selection (W. D. Hamilton)
- r > c/b
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
A. Kin Selection (W. D. Hamilton)
- r > c/b
- Coefficient of relatedness must exceed the cost/benefit ratio of the act.
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
A. Kin Selection (W. D. Hamilton)
- r > c/b
- Coefficient of relatedness must exceed the cost/benefit ratio of the act.
- So, dieing while saving three sibs (c/b = 1/3) is adaptive because the
coefficient between sibs is 1/2 (> 1/3).
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
A. Kin Selection (W. D. Hamilton)
B. Direct Reciprocity (Trivers 1971)
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
A. Kin Selection (W. D. Hamilton)
B. Direct Reciprocity (Trivers 1971)
- prisoners dilemma
B Stays Silent
B Betrays
A Stays Silent
both get 6 months A gets 10 years;
B goes free
A Betrays
B gets 10 years; A both get 2 years
goes free
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
A. Kin Selection (W. D. Hamilton)
B. Direct Reciprocity (Trivers 1971)
- prisoners dilemma So, cooperation pays...but blind sacrifice does not!
B Stays Silent
B Betrays
A Stays Silent
both get 6 months A gets 10 years;
B goes free
A Betrays
B gets 10 years; A both get 2 years
goes free
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
A. Kin Selection (W. D. Hamilton)
B. Direct Reciprocity (Trivers 1971)
- in the "repeated prisoner's dilemma":
B Stays Silent
B Betrays
A Stays Silent
both get 6 months A gets 10 years;
B goes free
A Betrays
B gets 10 years; A both get 2 years
goes free
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
A. Kin Selection (W. D. Hamilton)
B. Direct Reciprocity (Trivers 1971)
- in the "repeated prisoner's dilemma":
- it's adaptive to cooperate if there are repeated interactions with the same partner
B Stays Silent
B Betrays
A Stays Silent
both get 6 months A gets 10 years;
B goes free
A Betrays
B gets 10 years; A both get 2 years
goes free
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
A. Kin Selection (W. D. Hamilton)
B. Direct Reciprocity (Trivers 1971)
- in the "repeated prisoner's dilemma":
- it's adaptive to cooperate if there are repeated interactions with the same partner
- it works by 'tit for tat' or 'hold if it pays' (if you start on cooperate)
B Stays Silent
B Betrays
A Stays Silent
both get 6 months A gets 10 years;
B goes free
A Betrays
B gets 10 years; A both get 2 years
goes free
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
A. Kin Selection (W. D. Hamilton)
B. Direct Reciprocity (Trivers 1971)
- in the "repeated prisoner's dilemma":
- it's adaptive to cooperate if there are repeated interactions with the same partner
- it works by 'tit for tat' or 'hold if it pays' (if you start on cooperate)
B Stays Silent
B Betrays
A Stays Silent
both get 6 months A gets 10 years;
B goes free
A Betrays
B gets 10 years; A both get 2 years
goes free
- cooperation can evolve only if w > c/b .... if the frequency of encounter
exceeds the cost/benefit ratio of the altruistic act. If this is the case, you may
profit in the future if the act is reciprocated (and if w is high, then there is
good chance it will be)
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
A. Kin Selection (W. D. Hamilton)
B. Direct Reciprocity (Trivers 1971)
- Mutualisms: both partners have increased fitness, relative to other
members of their species, by interacting with another species.
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
A. Kin Selection (W. D. Hamilton)
B. Direct Reciprocity (Trivers 1971)
- Mutualisms: both partners have increased fitness, relative to other
members of their species, by interacting with another species.
- Positive feedback can enhance the dependancy between partners
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
A. Kin Selection (W. D. Hamilton)
B. Direct Reciprocity (Trivers 1971)
- Mutualisms: both partners have increased fitness, relative to other
members of their species, by interacting with another species.
- Positive feedback can enhance the dependancy between partners
Atta cephalotes, the "leaf cutter"
ants, farm and eat a species of
fungus that lives nowhere else now.
Acacia and Acacia ants
Corals and zooxanthellae
Frugivory
Aphid farming by ants
Gleaners
Pollination
Protozoans in Termites
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
A. Kin Selection (W. D. Hamilton)
B. Direct Reciprocity (Trivers 1971)
C. Indirect Reciprocity (Nowak 1998)
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
A. Kin Selection (W. D. Hamilton)
B. Direct Reciprocity (Trivers 1971)
C. Indirect Reciprocity (Nowak 1998)
- In large populations (humans), the frequency of encounter may be low, and the
relationship is asymmetric (one person CAN help, the other may never be able to).
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
A. Kin Selection (W. D. Hamilton)
B. Direct Reciprocity (Trivers 1971)
C. Indirect Reciprocity (Nowak 1998)
- In large populations (humans), the frequency of encounter may be low, and the
relationship is asymmetric (one person CAN help, the other may never be able to).
- Helping establishes a good reputation; and increases the chance that others (not
the direct beneficiaries) will help us if we need it.
http://www.youtube.com/watch?v=frpp6DjCaJU
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
A. Kin Selection (W. D. Hamilton)
B. Direct Reciprocity (Trivers 1971)
C. Indirect Reciprocity (Nowak 1998)
- In large populations (humans), the frequency of encounter may be low, and the
relationship is asymmetric (one person CAN help, the other may never be able to).
- Helping establishes a good reputation; and increases the chance that others (not
the direct beneficiaries) will help us if we need it.
- People who are observed to be more helpful are more likely to be helped.
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
A. Kin Selection (W. D. Hamilton)
B. Direct Reciprocity (Trivers 1971)
C. Indirect Reciprocity (Nowak 1998)
- But in large populations (humans), the frequency of encounter may be low, and
the relationship is asymmetric (one person CAN help, the other may never be able
to).
- Helping establishes a good reputation; and increases the chance that others (not
the direct beneficiaries) will help us if we need it.
- People who are observed to be more helpful are more likely to be helped.
- Even in other species... Bshry 2006 - Cleaner Wrasse
- Even in other species... Bshry 2006 - Cleaner Wrasse
- wrasse eat parasites off "client" fish... but they can cheat and eat
mucous, which is bad for the client fish.
- Even in other species... Bshry 2006 - Cleaner Wrasse
- wrasse eat parasites off "client" fish... but they can cheat and eat
mucous, which is bad for the client fish.
- Client fish observe wrasses, and prefer the wrasses that don't cheat
- Even in other species... Bshry 2006 - Cleaner Wrasse
- wrasse eat parasites off "client" fish... but they can cheat and eat
mucous, which is bad for the client fish.
- Client fish observe wrasses, and prefer the wrasses that don't cheat
- AND, when WATCHED, wrasses cheat less and cooperate more...
- Even in other species... Bshry 2006 - Cleaner Wrasse
- wrasse eat parasites off "client" fish... but they can cheat and eat
mucous, which is bad for the client fish.
- Client fish observe wrasses, and prefer the wrasses that don't cheat
- AND, when WATCHED, wrasses cheat less and cooperate more...
- so wrasses cooperate with current clients to gain favor (reputation) with
others that are observing.
- Even in other species... Bshry 2006 - Cleaner Wrasse
- wrasse eat parasites off "client" fish... but they can cheat and eat
mucous, which is bad for the client fish.
- Client fish observe wrasses, and prefer the wrasses that don't cheat
- AND, when WATCHED, wrasses cheat less and cooperate more...
- so wrasses cooperate with current clients to gain favor (reputation) with
others that are observing.
- cooperation can only evolve IF q > c/b, where:
q = prob. of knowing someone's reputation
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
III. Conclusions
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
III. Conclusions
- cooperation can evolve as a result of selection; even among unrelated
entities (symbioses)
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
III. Conclusions
- cooperation can evolve as a result of selection; even among unrelated
entities (symbioses)
- when cooperation occurs at one level, it creates a new level of
organization... cells cooperate and ORGANISMS are produced... organisms
cooperate and SOCIAL UNITS are produced.
The Evolution of Cooperation
I. Issue
II. Mechanisms (Nowak, 2006, Science).
III. Conclusions
- cooperation can evolve as a result of selection; even among unrelated
entities (symbioses)
- when cooperation occurs at one level, it creates a new level of
organization... cells cooperate and ORGANISMS are produced... organisms
cooperate and SOCIAL UNITS are produced.
- Cooperation allows specialization, and creates diversity at several levels
Conflicts....
I. Among Relatives
Conflicts....
I. Among Relatives
A. Parent Conflicts
Conflicts....
I. Among Relatives
A. Parent Conflicts
- male parent (especially in multiply inseminated species) wants OWN
offspring to receive resources and grow large
Conflicts....
I. Among Relatives
A. Parent Conflicts
- male parent (especially in multiply inseminated species) wants OWN
offspring to receive resources and grow large
- female parent, nourishing many embryos, wants ALL her offspring to
survive and so does NOT want one to grow disproportionately.
Conflicts....
I. Among Relatives
A. Parent Conflicts
- male parent (especially in multiply inseminated species) wants OWN
offspring to receive resources and grow large
- female parent, nourishing many embryos, wants all offspring to survive
and so does NOT want one to grow disproportionately.
- Insulin-like Growth Factor II:
Conflicts....
I. Among Relatives
A. Parent Conflicts
- male parent (especially in multiply inseminated species) wants OWN
offspring to receive resources and grow large
- female parent, nourishing many embryos, wants all offspring to survive
and so does NOT want one to grow disproportionately.
- Insulin-like Growth Factor II:
- stimulates growth of embryo.
Conflicts....
I. Among Relatives
A. Parent Conflicts
- male parent (especially in multiply inseminated species) wants OWN
offspring to receive resources and grow large
- female parent, nourishing many embryos, wants all offspring to survive
and so does NOT want one to grow disproportionately.
- Insulin-like Growth Factor II and gene imprinting:
- stimulates growth of embryo.
- gene from male is ON; gene from female is OFF
Conflicts....
I. Among Relatives
A. Parent Conflicts
- male parent (especially in multiply inseminated species) wants OWN
offspring to receive resources and grow large
- female parent, nourishing many embryos, wants all offspring to survive
and so does NOT want one to grow disproportionately.
- Insulin-like Growth Factor II:
- stimulates growth of embryo.
- gene from male is ON; gene from female is OFF
- Also, there is an inhibitor to IGF-II
Conflicts....
I. Among Relatives
A. Parent Conflicts
- male parent (especially in multiply inseminated species) wants OWN
offspring to receive resources and grow large
- female parent, nourishing many embryos, wants all offspring to survive
and so does NOT want one to grow disproportionately.
- Insulin-like Growth Factor II:
- stimulates growth of embryo.
- gene from male is ON; gene from female is OFF
- Also, there is an inhibitor to IGF-II
- gene from male is OFF, gene from female is ON.
Conflicts....
I. Among Relatives
A. Parent Conflicts
- male parent (especially in multiply inseminated species) wants OWN
offspring to receive resources and grow large
- female parent, nourishing many embryos, wants all offspring to survive
and so does NOT want one to grow disproportionately.
- Insulin-like Growth Factor II:
- stimulates growth of embryo.
- gene from male is ON; gene from female is OFF
- Also, there is an inhibitor to IGF-II
- gene from male is OFF, gene from female is ON.
- Infanticide by adoptive parents ... male lions kill cubs and bring female into estrus
Conflicts....
I. Among Relatives
A. Parent Conflicts
- Red Deer
- In poor years, small doe's selectively abort male embryos at a higher
frequency than female embryos. (In a harem forming species, males are unlikely to
mate; especially if they are small).
Conflicts....
I. Among Relatives
A. Parent Conflicts
- Red Deer
- In poor years, small doe's selectively abort male embryos at a higher
frequency than female embryos. (In a harem forming species, males are unlikely to
mate; especially if they are small).
- But males with high
breeding success (probability of
mating, fertility, and proportion of
normal sperm) can influence sex
ratios also; they produce more sons.
(Gomendio et al., Science. 2006.)
Conflicts....
I. Among Relatives
A. Parent Conflicts
- Red Deer
- In poor years, small doe's selectively abort male embryos at a higher
frequency than female embryos. (In a harem forming species, males are unlikely to
mate; especially if they are small).
- But males with high
breeding success (probability of
mating, fertility, and proportion of
normal sperm) can influence sex
ratios also; they produce more sons.
(Gomendio et al., Science. 2006.)
- So, in this system,
females often maximize production
of daughters, while males maximize
production of sons.
Conflicts....
I. Among Relatives
A. Parent Conflicts
B. Parent-Offspring Conflicts
Conflicts....
I. Among Relatives
A. Parent Conflicts
B. Parent-Offspring Conflicts
- Parents are concerned with their cumulative fitness; including
potential future fitness... not the survival of each and every offspring.
Conflicts....
I. Among Relatives
A. Parent Conflicts
B. Parent-Offspring Conflicts
- Parents are concerned with their cumulative fitness; including potential
future fitness... not the survival of each and every offspring.
- Obviously, each offspring is concerned with THEIR OWN survival
Conflicts....
I. Among Relatives
A. Parent Conflicts
B. Parent-Offspring Conflicts
- Parents are concerned with their cumulative fitness; including potential
future fitness... not the survival of each and every offspring.
- Obviously, each offspring is concerned with THEIR OWN survival
- Birds often lay more eggs than they can care for, on average. If it is a
good year, they can take advantage and raise more chicks. If it is a poor or average
year, the last chick to hatch will die.
Conflicts....
I. Among Relatives
A. Parent Conflicts
B. Parent-Offspring Conflicts
- Parents are concerned with their cumulative fitness; including potential
future fitness... not the survival of each and every offspring.
- Obviously, each offspring is concerned with THEIR OWN survival
- Birds often lay more eggs than they can care for, on average. If it is a
good year, they can take advantage. If it is a poor or average year, the last chick to
hatch ends up dieing.
- Red Deer: in poor years, small doe's selectively abort male embryos at
a higher frequency than female embryos. (In a harem forming species, males are
unlikely to mate; especially if they are small).
Conflicts....
I. Among Relatives
A. Parent Conflicts
B. Parent-Offspring Conflicts
C. Sibling Conflicts
Conflicts....
I. Among Relatives
A. Parent Conflicts
B. Parent-Offspring Conflicts
C. Sibling Conflicts
- siblicide occurs where resources are
limiting, or social dominance is a priority.
Conflicts....
I. Among Relatives
A. Parent Conflicts
B. Parent-Offspring Conflicts
C. Sibling Conflicts
- siblicide occurs where resources are
limiting, or social dominance is a priority.
- Cattle Egrets ...lay three eggs; first two
have high androgens. If food is limiting, they will
kill the third chick
Conflicts....
I. Among Relatives
A. Parent Conflicts
B. Parent-Offspring Conflicts
C. Sibling Conflicts
- siblicide occurs where resources are
limiting, or social dominance is a priority.
- Cattle Egrets ...lay three eggs; first two
have high androgens. If food is limiting, they will
kill the third chick
- Hyenas... same sex siblicide more
common than female-male; matriarchal society
Conflicts....
I. Among Relatives
II. Among Non-Relatives
A. Interspecific Competition
Conflicts....
I. Among Relatives
II. Among Non-Relatives
A. Interspecific Competition
- within both populations, those
that are competing within AND between
species are at an energetic and
reproductive disadvantage.
Conflicts....
I. Among Relatives
II. Among Non-Relatives
A. Interspecific Competition
- within both populations, those
that are competing within AND between
species are at an energetic and
reproductive disadvantage.
- competititive exclusion
Conflicts....
I. Among Relatives
II. Among Non-Relatives
A. Interspecific Competition
- within both populations, those
that are competing within AND between
species are at an energetic and
reproductive disadvantage.
- competititive exclusion
- niche partitioning
Conflicts....
I. Among Relatives
II. Among Non-Relatives
A. Interspecific Competition
- within both populations, those
that are competing within AND between
species are at an energetic and
reproductive disadvantage.
- competititive exclusion
- niche partitioning
Conflicts....
I. Among Relatives
II. Among Non-Relatives
A. Interspecific Competition
- within both populations, those
that are competing within AND between
species are at an energetic and
reproductive disadvantage.
- competititive exclusion
- niche partitioning;
character displacement
Both species benefit by reducing the
interaction; once it is reduced, there
is no benefit to reestablish the
interaction.
Life History Evolution
I. Components of Fitness and Trade-Offs
A. Components
Life History Evolution
I. Components of Fitness and Trade-Offs
A. Components
1. probability of survival
Life History Evolution
I. Components of Fitness and Trade-Offs
A. Components
1. probability of survival
2. number of offspring
Life History Evolution
I. Components of Fitness and Trade-Offs
A. Components
1. probability of survival
2. number of offspring
3. quality of offspring (probability of their survival)
B. Trade-Offs
1. survival and growth vs. reproduction: 'r' vs. 'K' strategists
"K"OMPETITIVE
ABILITY
BASAL METABOLISM
GROWTH
"r"
REPRODUCTION
B. Trade-Offs
1. survival and growth vs. reproduction: 'r' vs. 'K' strategists
2. # vs. quality of offspring lots of little or a few big
B. Trade-Offs
1. survival and growth vs. reproduction: 'r' vs. 'K' strategists
2. # vs. quality of offspring lots of little or a few big
3. Timing: annual vs. perennial life history
B. Trade-Offs
1. survival and growth vs. reproduction: 'r' vs. 'K' strategists
2. # vs. quality of offspring lots of little or a few big
3. Timing: annual vs. perennial life history
- When all else is equal, reproducing early and often is adaptive;
even if it kills you. The faster you create copies that can copy themselves,
the more the "compounding interest" effect of exponential reproduction can
get working for you.
Aphid "stem mother" produces live offspring asexually...
- But if that's true, why are there perennials?
Because environment matters. Lots of small offspring means that they only
survive in a benign environment. But some environments are not benign...
so the only way to reproduce successfully is to produce larger offspring...
which may require longer survival to accumulate resources to make large
offspring.
- But if that's true, why are there perennials?
Because environment matters. Lots of small offspring means that they only
survive in a benign environment. But some environments are not benign...
so the only way to reproduce successfully is to produce larger offspring...
which may require longer survival to accumulate resources to make large
offspring.
- Or, as a consequence of storing energy, you may be able to
reproduce disproportionately more later and 'recoup' the losses of delaying
reproduction.
1
2
3
4
Annual
1
100
10,000
1,000,000
Perennial
(Redwood)
0
0
0
1,000,001
each year
B. Trade-Offs
1. survival and growth vs. reproduction: 'r' vs. 'K' strategists
2. # vs. quality of offspring lots of little or a few big
3. Timing: annual vs. perennial life history
C Evidence of Trade-Offs
1. Fruit flies - delay reproduction and extend their lifespan
B. Trade-Offs
1. survival and growth vs. reproduction: 'r' vs. 'K' strategists
2. # vs. quality of offspring lots of little or a few big
3. Timing: annual vs. perennial life history
C Evidence of Trade-Offs
1. Fruit flies - delay reproduction and extend their lifespan
2. Blue tits - more chicks, shorter lifespans
B. Trade-Offs
1. survival and growth vs. reproduction: 'r' vs. 'K' strategists
2. # vs. quality of offspring lots of little or a few big
3. Timing: annual vs. perennial life history
C Evidence of Trade-Offs
1. Fruit flies - delay reproduction and extend their lifespan
2. Blue tits (birds) - more chicks, shorter lifespans
3. Crickets - short-winged morphs (decreased survival and less
growth energy) have larger eggs; long-winged forms have smaller eggs
B. Trade-Offs
1. survival and growth vs. reproduction: 'r' vs. 'K' strategists
2. # vs. quality of offspring lots of little or a few big
3. Timing: annual vs. perennial life history
C Evidence of Trade-Offs
1. Fruit flies - delay reproduction and extend their lifespan
2. Blue tits (birds) - more chicks, shorter lifespans
3. Crickets - short-winged morphs (decreased survival) have larger
eggs; long-winged forms have smaller eggs
4. Trade-offs between offspring size and number within species
size
number
B. Trade-Offs
1. survival and growth vs. reproduction: 'r' vs. 'K' strategists
2. # vs. quality of offspring lots of little or a few big
3. Timing: annual vs. perennial life history
C Evidence of Trade-Offs
1. Fruit flies - delay reproduction and extend their lifespan
2. Blue tits (birds) - more chicks, shorter lifespans
3. Crickets - short-winged morphs (decreased survival) have larger
eggs; long-winged forms have smaller eggs
4. Trade-offs between offspring size and number within species
5. Is there an optimal offspring size?
- Probably a balance between selection on offspring survival (large
size) and parental fitness (increased number).
- Benign env... maximize number
- Harsh env... maximize size