Titfor tat is an ESS when:

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Tit-for -tat is an ESS when
(?-?) ?
c b
gt
Reciprocal altruism
Cooperation is an ESS when
Kin selection
r gt c/b
where r coefficient of relatedness
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Genetic contribution
Relatedness
r 1.0 0.5 0.25 0.125
identical twin full-sib, parent half-sib,
niece/nephew, grandparent cousin
Less likely to cooperate
The true value of Hamiltons Rule is the concept
of inclusive fitness (IF) IF measure of fitness
of the bearer plus the effect it has on genetic
relatives
Sacrificial behavior that is difficult to explain
solely from the bearers perspective now makes
sense in terms of the genes
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Naked mole rat and eusociality
Eusociality - communal care of young -
over-lapping generations - division of labor
A single Queen and 1-3 males with breeding
rights for the colony
Shorter-living non-reproductive show a variety of
cooperative behaviors - tunnel digging -
debris sweeping - grooming - defense
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WHY?
Genetic relatedness
r 0.81
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Hymenoptera Ants, bees, wasps
Make up the majority of the eusocial insects
(also Termites and an aphid)
Haplodiploidy genetic system
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Haplodiploidy genetic system
Males develop from unfertilized eggs and are
haploid therefore all of a males sperm are
identical and the probability of sharing genes
via the father is 1.0
Females develop from fertilized eggs and are
diploid therefore the probability of sharing
genes via the mother is 0.5
Sister-sister relatedness Via mother 0.5 ?
0.5 0.25 Via Father 0.5 ? 1.0 0.5
Total 0.75
Sisters are more closely related to one another
than they are to their own offspring !!
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Honey bees (polyandrous)
Who would you prefer to be the mother of the
hives males?
Herself Queen Random worker
r 0.5 own son r 0.25 Queens son r lt 0.25
workers son
60,000 individuals easily
Why does the hive cooperate and workers dont
try to produce sons?
Its self-policing and workers kill each others
sons any egg not marked with Queens pheromones
gets eaten
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Bumble bees (monogamous)
The prior logic holds
Who would you prefer to be the mother of the
hives males?
Herself Random worker Queen
r 0.5 own son r 0.25 Queens son r lt 0.375
workers son
150 workers
When its time to produce males workers raise
workers sons not Royal sons
This disharmony explains smaller bumble bee
colonies and why they break-up at the end of each
season
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COOPERATIVE BREEDING
Communal breeding in the Azure-winged Magpie
A rare reproductive strategy found in lt 3
birds (200 spp) and 120 spp of mammals. Why
should individuals forego their own reproduction
to assist in helping others???
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Basic Terminology
Cooperative Breeding the presence of
non-breeding individuals, in a stable social
unit, which assist breeding adults in the care of
young birds Helpers Non-breeding individuals
that assist in raising the young, defending a
territory or other important resources.
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Helping can be viewed as beneficial for the
helper in 1 of 2 ways (1) Helpers gain
indirect, genetic benefits, i.e., inclusive
fitness by promoting the welfare and
reproductive success of kin (kin selection)
(2) Direct - Helpers gain (now or delayed) direct
benefits by directly gaining something important
to their own future success helpers need not
increase Rep. Success of the adults may be
unrelated
Both probably occur to differing degrees in most
cases
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As predicted by Kin Selection WF bee-eaters
more frequently help more closely related kin
How they recognize close kin remains an open
question
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Do Helpers really help? -- critical if indirect
benefits are occurring

• examine young/nest with and w/o helpers or
  correlate nest productivity
• with helpers and if there is an increase we
  can surmise that helpers help

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Example II
FL scrub Jay Breeding pairs have an average of
1.8 helpers, typically 1-2 yr-olds related to the
adults
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Why did helping help?
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Conclusion is... HELPERS really do HELP
But not enough.. so why is there cooperative
breeding???
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Why dont helpers breed on their own? (why delay
dispersal)
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FL Scrub Jay Woolfenden and Fitzpatrick studies
showed male scrub jays inherit a part of their
fathers territory budding
A 1st generation B, C sons of A D son of B
(grandson of A)
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What about unrelated helpers?
Helpers can also be a threat - In Reyers
studies of the Pied Kingfisher, 7 of 17 helpers
surviving to breed, bred with the female they
helped (these are secondary, unrelated
helpers) 3 of which displaced the older male
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If there are costs to keeping offspring around,
or in cases where helpers are unrelated,
helping may be extorted for use of a territory.
...if the adults will have you paying Extortion
Fees
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In some cases, the helper may get the upper hand
and one bird may have to pay a cost of
appeasement in the form of mating opportunities
to keep the helper, e.g., Acorns
Woodpeckers
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Acorn woodpeckers in fact have a complex society
consisting of multiple breeders of both sexes and
non-breeding helping -- Communal breeding with
Helpers. In this species the strong social
bonds are required to defend territories and
acorn granaries where they are critical
resources not NM, Central and South Am.
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The discussion about extortion and
appeasement might suggest that social and
cooperative systems are filled with conflicts
and this is certainly true. Acorn Woodpecker
males are known for their reproductive skew
most offspring comes from a dominant male
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Summary

• Cooperative breeding is one example of
  group-living behavior
• Both parties benefit through a combination of
  direct and indirect
• benefits and immediate or potential future
  benefits
• (3) But it is also ripe with plenty of selfish
  behavior (extortion, appeasement)

• benefit is high, but not that high
• cost is low small chance of reproducing
  yourself
• higher degree of relatedness

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Black-backed Jackal (Canis mesomelas)
The Serengeti environment provides few
opportunities to breed, and many pairs
retain young from the previous 1-2 litters.
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Helpers assist in regurgitating food, lactating
(females), grooming, playing, defense of the
young
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