FUCKING FINAL Flashcards
How does sociality evolve?
Sociality only evolves if it results in an individual in a group obtaining higher fitness than it would living alone
AKA Net Benefits > Net Costs
What re the Benefits of Sociality
1) Increased diet breadth for predators
2) Increased ability to find resources
3) Decreased search time to find food or mates
4) Decreased predation
5) Decreased physiological costs of movement in air or water
6) Decreased physiological costs of thermoregulation via huddling
7) Division of labor: individuals can specialize on different tasks (food acquisition, nest defense, etc.)
8) Communal care of young: enhanced feeding and defense of offspring
Costs of Sociality
1) Increased competition for resources
2) Increased opportunity for aggressive behavior
3) Increased likelihood of pathogen transmission
Minnow Foraging Study
As schoal size increases, the average foraging time decreases
This study demonstrates how it is often harder for lone animals to find food, thus sociality provides foraging benefits
Insects/Bees Foraging Study
Bees share up-to-date information about floral resources in the local environment
Demonstrating foraging benefits of sociality
Coyote Experiment
Coyotes living in larger groups have a greater volume of larger prey items in their scat, and a decrease in smaller prey
Foraging benefits of sociality: increased capture
Aerodynamic Benefit: Reduced cost of movement in pelicans
Research Question: Why do large birds fly in a V-formation?
Hypothesis: This formation reduces the cost of flying
Prediction: Birds in formation will have a lower wingbeat frequency and heart rate than solitary birds
Methods:
1) Placed heart rate monitors on trained white pelicans
2) Videotaped flight formations, collected data on wingbeat frequency and location of each bird in formation
Results: Birds in formation behind the leader had a slower wingbeat frequency and lower heart rate; still not as low as gliding though
Conclusion: Birds can thus reduce flight costs by flying in V-formation
The cost of sociality: Competition
Therefore competition for resources can limit group size, in which:
1) Low-resource environments will have smaller group sizes than high-resource environments
2) Positive relationship between resources in a Habitat and Group Size
Group Size and Competition in Primates – red colobus monkeys and red-railed guenons
Research Question: Does competition affect the size of social groups?
Hypothesis: Competition for food limits group size
Prediction: Low-resource environments should have smaller group sizes than high-resource environments
Methods:
Monkeys were fed a variety of fruits and vegetation
Group size ranged from <10 to >36
Each month, recorded the density of food trees on transects and the average group size of each species i four different sites
Results:
Average group size was positively correlated with the density of food trees
Conclusion: Competition for food appears to be associated with group size
The Cost of Sociality: Disease Transmission
Parasites and pathogens can reduce an animal’s fitness;
Transmitted by close contact;
Disease transmission rates should increase with group size;
Positive correlation between group size and proportion of infected individuals
Sociality and disease transmission in guppies
Research Question: How does sociality affect disease transmission?
Hypothesis: Tighter spacing between individuals enhances disease transmission
Prediction: Disease transmission rates will be higher in tighter social groups
- Guppies live in shoals (schools)
- Frequently infected with worms
- Females are more social – provides an opportunity to test how sociality/group spacing affects disease transmission
Methods:
- Removed all external parasites
- Created single-sex groups of sex
- Recorded average nearest neighbor distance in each school
- On 3rd day, infected a single fish in each school with 100 parasitic worms
- Recorded the spread of parasitic worms to other school members after three days
Results:
1) Females spent more time shoaling than males, and nearest neighbor distance was smaller in females than male groups
2) A higher proportion of females became infected than males
Conclusion: Disease transmission is affected by degree of sociality; this is a cost of group living/sociality
Do costs affect all members of a group equally?
NOOOOOOOOOOO
In the case of aggression, the better competitor wins an interaction, with boy parties receiving differing levels of risk of injury
How is aggression reduced in a group?
Dominance Hierarchy: An organized social system with dominant and subordinate members
How aggressive interactions affect stress, and how it is affected by the dominance hierarchy
Adrenal glands secrete glucocorticoids in response to help utilize fat stores to deal with that stress;
chronic glucocorticoids secretion can negatively affect health and reproduction = COST OF AGGRESSION
If dominance hierarchies help reduce aggression, it should also reduce stress;
Conversely, disruption in hierarchy could increase stress
Stable Dominance Hierarchies and Stress in Baboons
Research Question: How do do dominance hierarchies affect stress levels?
Hypothesis: The formation of a dominance hierarchy reduces aggression and stress in individuals
Prediction: Aggression level and stress hormones such as glucocorticoids will be lowest when stable hierarchies exist
Methods:
1) Observed chacma baboons; noted periods when stable dominance hierarchies existed and other periods when changes occurred
2) Collected fecal samples and characterized glucocorticoid levels of individuals
Results:
1) Aggression was lowest during stable periods
2) Fecal glucocorticoid levels were also lowest during stable periods
Conclusion: Aggression and stress levels are lowest during periods when dominance hierarchies are stable
Animal Altruism
A behavior that results in the increased fitness of another individual and involves a cost to the individual performing the behavior;
AKA Helping Behavior
Is often directed towards close kin
Inclusive Fitness
An individual’s genetic success (progeny produced) plus the genetic success of its relatives (which share a portion of the individual’s genes)
Helping a close kin increases inclusive fitness
Kin Selection
Natural selection for behavior by individuals that may decrease their own survival or reproductive success, but increases that of their kin (who share a portion of their genes);
Based off of inclusive fitness
Hamilton’s Rule and Kin Selection
States that altruism only evolves when B x r (relatedness) > C
B x r = the amount of altruist’s genes passed on through helping behavior
Degree of relatedness chart
Parent-offspring: 0.5 Sibling-Sibling: 0.5 Grandparent-grandchild: 0.25 Aunt/Uncle-Nephew/Niece: 0.25 First Cousins: 0.125 Friends: 0
Testing Hamilton’s Rule: Altruistic Turkeys
Male turkeys may form social coalitions (a pair of males) and display together to attract females;
BUT only the dominant male mates
Research Question: Why do subordinates in social coalitions help the dominant male?
Hypothesis: Kin selection explains the helping behvior
Prediction: For a subordinate male: B x r > C
Methods:
1) Captured and marked individual turkeys, collected blood
2) Determined degree of relatedness among coalition males
3) Determined reproductive success of males in coalitions vs. solo males
Results:
1) Coalition males were close relatives (r = 0.42)
2) Solo males sired on average 0.9 offspring per male = C
3) Dominant males sired 7 offspring = B (6.1 more than solo males)
Thus,
(B x r) > C
[(6.1 x 0.42) = 2.56 > 0.9]
Conclusion:
Kin selection and Hamilton’s rule explain helping behavior by subordinate male turkeys
Kin Discrimination Hypotheses: How individuals discriminate kin from non-kin
1) Direct Familiarization – Individuals learn to discriminate kin from non-kin via previous associations
2) Indirect Familiarization – Individuals learn a reference phenotypic cue from themselves or known close relative. They then assess the degree of similarity of the learned cue to the cue in others.
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Research Question: How do stickle-backs discriminate kin from non-kin?
Hypothesis: Sticklebacks discriminate kin from non-kin through association
Methods: Raised individuals with all kin or with both kin and non-kin
Experiment 1) Tested fish raised with all kin for preferences to associate with a group of familiar kin vs. (unfamiliar) non-kin
Experiment 2) Tested fish raised with kin and non-kin for preference to associate with familiar kin vs. unfamiliar non-kin
Results:
1) Individuals reared with only kin preferred to associate with familiar kin over unfamiliar non-kin
2) Individuals reared with both kin and non-kin did not display any preference between familiar kin and familiar non-kin
Conclusions: Stickleback learn kin via prior associations
ASK: Does this not count as direct familiarization?
Cooperative Breeding
A situation in social groups in which adults physiologically capable of reproducing forgo breeding and instead help others to raise offspring
- Helpers do not reproduce; they pay a cost of care and so are exhibiting altruistic behavior
Possible helper benefits of cooperative breeding
1) Increases inclusive fitness (if helpers are related)
2) Ecological constraints (get group benefits while waiting for better breeding conditions/opportunities in the future)
Cooperative reproduction in long-tailed tits
Observation: Long-tailed tits with predated nests often help feed another pair’s young
Research Question: Why do some adult long-tailed tits within a social group help other adults to raise their offspring?
Hypothesis: Kin selection explains the evolution of helpers at the nest
Prediction: Helpers are close relatives of the adult breeders
Methods:
- Performed observations on birds of known relatedness
- Noted instances of helping behavior and long-term survivorship of nestlings (recruitment into a social group the following year)
Results:
1) Helpers assisted pairs that contained at least one relative; in 90% of cases, they were close relatives
2) The probability of recruitment of a young the following year increased with the number of helpers at their nest
Conclusion: Kin Selection explains the helping behavior in these birds; helpers benefit by increasing their inclusive fitness
Cooperative reproduction and social queuing in clownfish
Clownfish exhibit sequential hermaphroditism (sex of individuals change as the develop)
- Schools form a hierarchy with a breeding, female fish at the top – and a breeding male below
- Other fish in the group are subordinate and do not breed, but help defend the territory
Hypothesis: Subordinates can move up the dominance over time, a process known as social queuing
Prediction: Subordinates will obtain future reproductive benefits by staying in their group
Methods: Observed 97 social groups of clownfish;
Noted recruitment of new fish, changes in breeding status;
Experimentally manipulated 16 groups by removing the breeding male and observed changes in social status
Results:
1) When breeding female is lost, the breeding male changed sex and became the breeding female
2) Removal of breeding male resulted in the next-highest-ranking non-breeder to become a reproductive male
3) Any new recruits always entered the group as the most subordinate member
Conclusion: Subordinate group members can eventually achieve dominant reproductive status via social queuing
Eusociality, criteria, and and it forms
Extreme altruism
Includes:
1) Overlapping generations
2) Cooperative brood care by non-parents
3) A reproductive division of labor; some adults reproduce while others do not (they are sterile) and care for the young of others
Forms castes: morphologically and behaviorally distinct individuals within eusocial groups
Hypotheses of how eusociality forms in Hymenoptera (bees, wasps and ants)
1) Haplodiploidy Hypothesis: Haplodiploid genetic systems
– Males develop from unfertilized eggs (Haploid)
– Females develop from fertilized eggs (Diploid)
In which sisters share 50% genes from father and either 50%/0% from mother – averaging 75% shared genes amongst sisters; kin selection and inclusive fitness is high, thus help queen produce more offspring
REFER TO PAPER
Haplodiploidy Hypothesis
The evolution of eusociality in Hymenoptera is based on their haplodiploid genetic system;
But can not explain evolution of sterile castes in many non-Hymenoptera species, such as termite;
Most likely due to a combination of kin selection and ecological constraints
Byproduct Mutualism
When an individual’s cooperative behavior enhances both its own fitness and the fitness of others;
Is often the explanation for unrelated altruism;
Evolves via direct reciprocal altruism (direct reciprocity)
Direct Reciprocity
A helps B in one encounter and then B helps A in a future encounter
- Both individuals eventually receive a benefit that exceeds the cost of helping
How does Direct Reciprocity Evolve?
Repeated interactions provide the opportunity for reciprocity
- “Tit-for-tat” strategy: a player always cooperates in the first interaction with a specific partner
- In later interactions, each matches the behavior of the other from the previous interaction
- When two players use this strategy (ESS), it can achieve a high payoff –> Altruism can evolve
Required conditions:
1) Individuals must have the opportunity to interact repeatedly
2) The fitness benefit received must exceed the cost of helping
3) Individuals must be able to recognize one another in order to reciprocate
Audience effect
Occurs when the presence of bystanders influence the behavior of a signaler
Dispersal
Short-distance, one-way movements to a new area;
Reduces inbreeding and competition for resources (Competition hypothesis and Inbreeding Avoidance Hypothesis)
Natal Dispersal: Movement away from an individual’s place of birth; one-time event
Breeding dispersal: Looks for best mating sites; Opposes site fidelity
Migration, and its cost/benefits
Long-distance, two-way movements
Costs and benefits of migrating:
- Benefits: Move to an area with more favorable conditions
- Costs: Loss of time and energy, risk of predation, injury, etc.
Costs and benefits of staying in one location:
- Benefits: Do not pay costs and incur risks of long distance movement
- Cost: must endure harsher conditions in current habitat
Three conditions required for evolution of behavior
1) Variability: variation in behavior among individuals
2) Heritability: some of these behavioral variants are in
Why migrate? What is the evolutionary premise?
Due to changes in the environment
If some individuals have higher fitness when migrating, then the population may exhibit partial migration
If all individuals have higher fitness, then the entire population will become migratory
Types of partial migration
Some are year-round residents (non-migrants)
Others exhibit seasonal migratory behavior
Fixed Polymorphism
When partial migration is displayed year after year
1) Migratory behavior could be a fixed, genetic trait of individual, and 2 genotypes are maintained by frequency-dependent selection
2) Migratory behavior could be dependent on individual condition: all individuals have the genetic disposition, but migratory behavior is only expressed in some; like the more unfit in pop
Orientation vs Navigation
Orientation is determining and maintaining a proper direction
Navigation is determining a particular location and moving toward it
Both useful for migration
Multimodal Orientation
Use of multiple compass systems at once to orient and navigate to a particular location
- Sun Compass
- Geomagnetic Compass
- Star Compass
Bicoordinate Navigation
The ability to identify a specific geographic location using two varying environmental gradients
Reciprocal Altruism in Vampire Bats
Explains food sharing in bats
Observed blood sharing interactions when the deprived bat was returned to the group
Food sharing occurred in unrelated bats, especially if prior food had been received from the recipient in the past
May have evolved as a form of direct reciprocity
Indirect reciprocity, and what is used to determine this
A helps B, because B helped C in the past
Individuals keep track of other individual’s reputation for helping = an image score
Cleaner Fish Reputations; Indirect Reciprocity
Cleaner fish feed on ectoparasites on client fish, but some will try to eat mucus
Client fish solicit cleaner fish
Client fish can observe interactions and form image scores of cleaner fish
Research Question: Is there any evidence that animals use their image scores to modify altruistic behavior?
Methods:
Observed interactions between cleaners and clients;
For each interaction, determined whether each cleaner cooperated or cheated;
Observed the behavior of the net client for that cleaner
Results:
When the next client arrived within six seconds, its behavior was affected by the previous interaction
Next clinet invited 100% of cooperative cleaner fish, and <25% of cheating cleaner fish
Conclusion:
Clients appear to form image scores of cleaners and assess their propensity to interact cooperatively
