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Inclusive Fitness
Vivian Hubby
Game Theory
• How can alternative reproductive
strategies exist?
• Game theory evaluates alternative
strategies where the outcome depends not
only on each individual’s strategy, but
also on the strategies of other individuals.
Game Theory With Side-Blotched
Lizards
• Most aggressive
• Large territories with
many females
Game Theory with Side-Blotched
Lizards
•Also territorial
•Defend smaller
territories with fewer
females
Game Theory With Side-Blotched
Lizards
•Nonterritorial
•Mimic females and
use “sneaky” tactics
to obtain matings.
Game Theory With Side-Blotched
Lizards
• The relative mating success of each male
type is not fixed but changes with the
relative abundance of the other male types
in the populations.
Beats
Beats
Beats
Altruism
• Altruism, or selflessness, occurs when
animals behave in ways that reduce their
individual fitness but increase the fitness
of other individuals.
Why Altruism?
• When parents sacrifice their own personal wellbring to produce and aid offspring, they increase
their own fitness by maximizing their genetic
representation in the population.
• Inclusive fitness is the total effect an individual
has on proliferating its genes by producing its
own offspring and by providing aid that enables
other close relatives, who share many of those
genes, to produce offspring.
Hamilton’s Rule
• B = benefit to the recipient, or the average
number of extra offspring that the beneficiary of
an altruistic act produces
• C = cost to the altruist, or how many fewer
offspring the altruist produces
• r = coefficient of relatedness, or the probability
that if two individuals share a common parent or
ancestor, a particular gene present in one
individual will also be present in the second
individual
• rB > C
Applying Hamilton’s Rule
• B = 2.0 children
• C = 5% chance
of drowning x 2
children = 0.1
• r = 0.5
• (0.5)(2.0) > (0.1)
• 1 > 0.1
Kin Selection
• Natural selection that favors altruistic
behavior by enhancing reproductive
success of relatives is kin selection.
• These genes for altruism will be passed on
as well.
Kin Selection in Nature
• Female Belding’s
ground squirrels settle
near their site of birth.
• Almost all alarm calls
are given by females,
and if a female’s close
relatives are dead, she
rarely gives alarm calls.
Reciprocal Altruism
• Reciprocal altruism is behavior characterized by
an individual aiding a non-relative that will return
the favor in the future.
• How can this evolve if many individuals will
cheat?
• Tit-for-tat: Individuals are always altruistic on the
first encounter and will continue to be that way
until they are cheated on. They will then retaliate
but will return to altruistic behavior when the
other individual becomes cooperative.
Social Learning
• Social learning: learning through observing
others
• Culture: a system of information transfer
through social learning or teaching that
influences the behavior of individuals in a
population
Social Learning of Alarm Calls
• Vervet monkeys have
distinct alarm calls when
they see leopards, eagles,
and snakes.
• Infant vervets make many
mistakes in their calls.
• They improve their
accuracy with age. They
learn how to give the right
call by observing other
members of the group and
receiving social
confirmation.
Mate Choice Copying
• Mate choice copying is a behavior in
which individuals in a population mimic
the mate choice of others.
• Females usually choose the more
orange males.
• If they see another female choose a
less orange male, they will choose it
over the more orange male.
• A female that mates with males that are
attractive to other females may increase
the probability that her male offspring
will also be attractive and have high
reproductive success.