Social Behavior I (social living) Flashcards
define social behavior
interactions among members of the same species
pros of social living
- division of labor
- protection/self-defense
- parental care
- foraging
- access to mates
- information - learning things from each other
cons of social living
- visibility to predators
- sharing resources
- spreading diseases
- mate and food competition
when should an individual join a group
- when benefits outweigh costs
- its not a constant choice, its selection acting
- needs VIST
4 kinds of social interactions
- mutually beneficial
- selfish
- altruism
- spite
4 kinds of social interactions - mutually beneficial
both actor and recipient benefits
4 kinds of social interactions: mutually beneficial- example
- many birds exhibit cooperative (communal) breeding
- group members are unrelated and all contribute to the eggs in the nest
- they have hair fitness than pairs and all individuals gain equal reproductive success
4 kinds of social interactions - selfish
- actor benefits
- recipient is harmed
4 kinds of social interactions: selfish - example
- cane toad tadpoles cannibalizing eggs
- Tadpole get nutrients and increases fitness
- Recipient (eggs) gets harmed
4 kinds of social interactions - altruism
- actor is harmed and recipient benefits
- Spending your own (energy, food, space, time, etc.) for the sake of somebody else’s fitness
4 kinds of social interactions: altruism - example
- Ground squirrels give an alarm call when they see a predator.
- It draws attention to them and allows the other squirrels in the colony to run and hide.
- They may die.
4 kinds of social interactions: altruism - when does it evolve
- evolves when there are benefits to both the donor and the recipient
- but its not always so obvious how it benefits both
4 kinds of social behavior - spite
both parties are harmed
4 kinds of social behavior: spite - example
- E. coli produce proteins that are lethal to other members of the same species
- But it can harm them
Hypotheses to explain apparent altruism
- Delayed competition (selfish teamwork)
- Stolen aid
- Social contract models
- Kin selection
- Multilevel selection
altruism hypothesis - delayed competition (selfish competition)
- Individuals work together
- If they don’t, they will not be able to
- Temporary – not true altruism
altruism hypothesis - stolen aid
- It’s not the choice of the individual
- Frequent in hierarchical societies
- Dominant individual will use violence to force a subordinate individual to cooperate
altruism hypothesis - Social Contract Models
- Tit for Tat: I’ll help you now and you’ll help me next time
- Theoretical model w very little evidence to support
- Reciprocal altruism – if it happens over time
altruism hypothesis: Social Contract Models - Generally, what was thought to be reciprocal altruism was…
- Kin selection
- Immediate reciprocation where no long term memory is involved
altruism hypothesis - kin selection
- Inclusive fitness: an animal’s reproductive output plus any reproduction added due to helping others
- Inclusive fitness = Direct fitness + Indirect fitness
altruism hypothesis: kin selection - relatedness
- mother-offspring: 1/2 of your genes
- sister-brother: 1/2 of your genes
- uncle-nephew: 1/4 of genes
- cousin-cousin: 1/8 of genes
altruism hypothesis: kin selection - hamilton’s rule
- We can predict when altruism should evolve by taking into account cost to donor (c), benefit to recipient (b), and relatedness (r) to recipient
- b*r – c > 0
- If r = 1/2, b needs to be more than half the cost (c)
Studying Hamilton’s rule in nature - prairie dogs sentry behavior
- found that both male and female are more likely to do call if they have relatives (genes) within the group
- also found that this isn’t due to parental care: still had same results regardless of stage of life (parent or child)
Studying Hamilton’s rule in nature: prairie dogs sentry behavior - male alarm call based on life stages
- alarm call is based on how close they are to relatives
- when living with a new group – no alarm call
- but once they start breeding – calling starts again
Studying Hamilton’s rule in nature - squirrel adopting behavior
- If no relatives are in the area, orphans were not adopted
- They only adopt related orphans
Studying Hamilton’s rule in nature: squirrel adopting behavior - when did they adopt (costs/benefits view)
Costs were less than indirect benefits (based on relatedness of babies they could adopt) – female did adopt
Costs were more than benefits – female did not adopt
altruism hypothesis: kin selection - Do individuals need to be able to recognize kin for kin selection to occur?
yes, need kin recognition mechanisms
altruism hypothesis: kin selection - what is kin recognition
- Generally based on “phenotype matching” (Smells like me, Makes a call like me)
- Or… Smells like my family and Makes a call like my family
altruism hypothesis: kin selection - what is the difference between kin recognition and individual recognition
- kin recognition involves recognizing genetic relatedness
- individual recognition is a general term for recognizing individuals or categories of conspecifics
what is the concept behind Greenbeard
- Null model where there is no kin selection
- gene that codes for a trait that is coupled with the ability to recognize that trait and individuals with those traits have to be altruistic
altruism hypothesis: kin selection - when is the cost of working to gain indirect fitness low?
- If you do not have much direct fitness potential
- but if you can’t make babies, your fitness cost for helping your family make babies is zero.
- You cannot reduce your direct fitness by spending energy on relatives if your direct fitness is zero anyway
altruism hypothesis: kin selection - when does it count as indirect fitness
- your aid must allow for the survival and reproduction of related young that would not have happened without your help.
- have to contribute to the relatives survival
how can kin selection explain spite?
- The enemy of my enemy is my friend
- Harm non-relatives to help relatives
If kin selection explains spiteful behavior, what would you expect about the relatedness between actors and recipients?
- actors should harm non-relatives
- actors may have low direct fitness
altruism hypothesis - multilevel selection
- Group selection
- Explains altruism as an unequal mutual benefit, e.g. morality
- Selection on group may outweigh selection on individual
altruism hypothesis: multilevel selection - Simpson’s Paradox
- Selfish individuals have higher fitness
- but groups with fewer selfish individuals and more cooperators will also have higher fitness
altruism hypothesis: multilevel selection - selection can be between…
- genes within an individual
- individuals within a group
- groups within populations
altruism hypothesis: multilevel selection - Bacteria (Pseudomonas fluorescens) example
- they consume oxygen in medium so only thin layer at the top is habitable
- A mutation causes cells to secrete a polymer that forms a mat and helps them stay at the water surface
- but the polymer is metabolically expensive (has a cost)
multilevel selection: Bacteria (Pseudomonas fluorescens) example - what individuals have the highest fitness?
- Cheaters
- they get the benefit of the mat without contributing to its upkeep
- BUT if the proportion of cheaters grows too high, the mat disintegrates, and the entire group sinks
altruism hypothesis: multilevel selection - Bacteria that produces toxic chemicals example
- Only get evolution of altruism when there is a lot of variation in selfish vs cooperative individuals (small population sizes)
- Groups w most cooperators outcompete group with fewer cooperators
altruism hypothesis: multilevel selection - Plant example example
- researchers are trying to understand how selection on groups and individuals work together
- they selected for groups (of all plants) and for individual (at the same time)
- selection on group – works, group gets bigger leaf area
- but when there is no individual selection – reduces effect of group selection
