reciprocal altruism is the

evolution of altruism among non kin

most altruistic acts serve to

benfit the individual's close relatives, or kin

group selection

to explain the existence of altruism

Natural selection produces beneficial outcomes for whole group/species

If group selfish, they would die out quickly due to overexploitation, but altruist fitness would increase

individual selection

Group under attack via George Williams

Evolution works with individual selection not group, traits chosen for benefit of individual not group

three arguments against group selection to prevent group selection

-mutation

-immigration

-lack of an ability to predict future source availability

mutation

limited resources, mutated individuals use said mutation to advantage/offspring advantage (two eggs to three eggs given sufficient resources)

immigration

more eggs produced, could move away

Lack of an ability to predict future source availability

group selection assumes that individuals can predict food availability within population

Infanticide

Pop. size controlled via competition (individuals want control as much resource as possible), results in infanticide (male bears killing cubs/lions killing cubs to take over pride)

Coefficient of Relatedness

Important to evolution of altruism, vested interest in protect related individuals (siblings, offspring)

Hamilton’s Rule (THIS WILL BE ON FINAL)

rB>C

altruistic gene will be favored by natural selection

benefits received and given is greater than cost

Inclusive Fitness (important)

total # of gene copies passed on to relatives + reproductive output

Kin Fitness

behavior that lowers fitness of individual, but enhances fitness of relative

Eusociality

organisms that have reproductive division of labor, overlapping generations, and cooperative care of young

[ex.] Bees have female workers, male drones, only queen reproduces, males die shortly after

[ex.] Naked mole rats also exhibit similar behavior to bees (however both parents are diploid)

Males -> haploid, females -> diploid (haplodiploidy), females more related to

sisters than own offspring

coefficient of relatedness (r) of sisters is

0.50 (from father) + 0.25 (from mother) = 0.75

More advantageous for females to stay and care for sisters

Eusociality due to

lifestyle NOT genetics

Certain conditions for eusociality

• Individuals are confined to burrows or nests and escape is difficult.
• A dominant individual (i.e., queen) can prevent other individuals from reproducing.
• Food is abundant enough to support high concentrations of individuals.
• These conditions are also met in colonies of naked mole rats, which are diploid mammals.
• Females do not reproduce and only the queen (shown resting on workers) has offspring

Reciprocal Altruism

cost for altruism offset by likelihood of return benefit

[ex.] Female vampire bat will regurgitate some food to feed other females, high likelihood that behavior will be returned later

Prisoner’s Dilemma (can’t get the chart on here, but just look at the slide)

Games in nature, tit-for-tat strategy usually most stable (do what was done unto them)

players do unto others exactly as has been done unto them

Evolutionary Stable Strategy (ESS)

if adopted by population, cannot be invaded by alternative (rare) strategy

Group Living

Benefits usually outweigh costs

Benefits: Group defense (increased vigilance (many eyes hypothesis) and protection through numbers)

Scan Frequency vs. Scan Duration

Frequency decrease as group size increases

Not as supported: duration decreases as size increases

Group Living and Food

• Take down predators of bigger size
• Can exploit discoveries of other individuals in group
• Orca Example: More than enough food for 3, stable enough with 5, not enough food for 6

Selfish Herd

• William Hamilton (1971)
• Individuals in group will choose position in center for greatest protection (like sardines), bunch together when under attack

Foraging Behavior

To remain at food or seek out new source? - Analysis via optimality modeling (Animal should behave in way that maximizes behavior minus costs)

Optimizing foraging behavior

difference between energetic benefits of food consumption and the energetic costs of food gathering is maximized

Optimal Foraging Theory

• maximize benefits and minimize costs of food gathering -
• More net energy, greater reproductive success

[ex.] Northwestern crow example: only large whelks (fewest drops required to break open)

[ex.] Leafcutter ant example: larger ants only forage at night due to parasitic flies active during day, small ants forage during the day

NAO (North Atlantic Oscillation) and Effects

Basically causes more snow in north

Heavier snowfall -> bigger wolf packs -> decrease in moose pop. -> more trees due to reduced moose pop.

Territory

fixed area where individual excludes other members of own species via marking or aggression

Provides exclusive access to resource

Larger territory = more resource, but more to defend (Usually big groups only defend mating/nesting areas instead of entire territory)

Game Theory= refer to document in modules (WILL BE ON FINAL)

Conclusions made:

• Fighting strategy is frequency dependent.
• The ESS is often a mixture of different strategy types like Hawk, Dove, and Bourgeois.
• The ESS is dependent on the values of rewards.
• The frequency of Hawk behavior increases as the payoff increases. (frequency of duck increases as risk of injury increases)

Fisher’s principle

1:1 sex ration is ESS as fitness of one gender reduced when overproduction of that gender

Polygyny

one male with many females (elk, elephant seals)

Polyandry

one female with many males, usually bigger than males (black widows)

Promiscuous

both males and females mate with multiple females and males, respectively (bonobos, mollusks)

The more similar in appearance males and females are, the more of a

chance they are monogamous animals (golden eagles, swans, one species of mouse, etc.)

Monogamy

two hypotheses for monogamy

Mate-guarding hypothesis

males stay with females to prevent other males from being fertilized by other males (some types of beetles and dunnocks)

Male assistance hypothesis

males remain to help rear offspring (70% of bird species are monogamous)

Female enforced monogamy

females stop male partners from being polygamous (burying beetles)

Purple Martin EPC

• Older martins claim top levels of martin house
• Sing song to attract others
• Older martins then mate with females of less experienced males

Species in stable environments with uniform food distribution

territorial and monogamous are

Species in areas that occasional have overabundance of food (Also, birds that produce nidifugous young (eyes open with feathers on body) more likely to be polygynous)

polygynous [males bigger than females)

Resource-based polygyny

good nest sites in male territory (male lark buntings hold territories in shade -> females need shade for chicks to live)

Harem mating structures

common when females congregate in groups/herds (elephant seal harems)

Communal courting

leks, prairie chickens and mannikins

Polyandry

Honeybees, sandpipers (females defend territories, limited only by number of males to incubate eggs), hyenas (females usually bigger than males)

Intersexual selection

females choose males based on particular trait

Intrasexual selection

males fight each other over mates