Process of social evolution - part 2

Question 1

how can there be a -r ( r < 0 )

Answer 1

when an individual is recently dispersed into population

Question 2

Hamilton’s rule - variables in c < rb

Answer 2

• c is the offspring cost to the actor.
• b is the offspring gain by the recipient.
• r is relatedness of actor and recipient.

Question 3

How do interactions in nature impact the terms of Hamilton’s Rule, to tip the balance towards the evolution of altruistic acts and sociality?

Answer 3

• c and b are influenced by ecology and synergistic benefits of sociality
• The expected destabilizing effects of r can be manipulated

Question 4

explain how c and b are influenced by ecology

Answer 4

costs and benefits will depend on the context of the ecological conditions the individuals are in

Question 5

explain how c and b are influenced by synergetic benefits of sociality

Answer 5

societies can do things that individuals cannot do.

Question 6

how can the expected destabilizing effects of r be manipulated

Answer 6

it can be manipulated by the social context to achieve conflict resolution and make sociality more stable

Question 7

Any ecological factor that ____________________ of an altruistic act for the actor and ________________________ to the recipient will promote sociality.

Answer 7

• decreases the cost (↓c )
• increases the benefit (↑b)

Question 8

Main categories of ecological factors promoting sociality

Answer 8

1. Environmental stress.
2. Food supply.
3. Nest-site limitation.
4. Temporal facilitation.
5. Parasitism.
6. Predation.

Question 9

Many good examples of ecological factors promoting sociality come from animals that facultatively participate in ________________

Answer 9

cooperative breeding

Question 10

define cooperative breeding

Answer 10

temporary/juvenile helpers at a nest of related or unrelated individuals

Question 11

Greater environmental stress or unpredictability means that social acts will likely _____ and _____.

Answer 11

• ↓c
• ↑b

Question 12

environmental stress - social group acts like an _______________________.

Answer 12

environmental buffer

Question 13

environmental stress - without the social buffer

Answer 13

• the environmental harshness is likely to result in high adult and offspring mortality
• reproductive output of solitary life is low to none, so the cost of an altruistic act for the actor is very low

Question 14

environmental stress - with the social buffer

Answer 14

the reproductive output of those that do get to reproduce (b) is boosted by many individuals harvesting scarce resources

Question 15

environmental stress - example

Answer 15

• mole rat group size increases with greater variability in rainfall
• they experience greater stress from water shortage

Question 16

mole rats experience _______________ of reproductively capable individuals when environmental ___________

Answer 16

• more dispersal
• stress is low

Question 17

mole rats - selection favors ___________________ (more altruism) when
____________________________.

Answer 17

• larger groups sizes
• environmental stress is high

Question 18

_______________________________________ across different potential nesting sites promotes non-dispersal of offspring.

Answer 18

Variability and unpredictability of food

Question 19

food supply - costs

Answer 19

The dangers of starvation following dispersal make the cost of staying low (↓c).

Question 20

food supply benefits

Answer 20

↑b for reproductive individuals from the additional helpers finding scarce food

Question 21

food supply - example

Answer 21

Seychelles Warbler (type of bird) offspring stay as helpers at their natal nest if territory of group has high quality food resources, and if alternative equal-quality territories are not available

Question 22

____________ of suitable nesting sites results in ___________________________ and establishes a ____________________________________

Answer 22

• Scarcity
• non-dispersal by offspring
• social group around the natal nest.

Question 23

nest-site limitation - cost

Answer 23

• c associated with the social act of staying to help rear subsequent generations is lowered
• alternative is effectively homelessness (high risk) and no opportunity to reproduce.

Question 24

nest-site limitation - benefit

Answer 24

• b is boosted by economies of social foraging and offspring rearing
• boost in offspring rearing may be more substantial than just additive/ non-linear.

Question 25

nest-site limitation - example

Answer 25

In a species of Mexican paper wasp (Mischocyttarus mexicanus), reproductive females form social nests only when protected nesting sites are limited

Question 26

Length of __________________ can dictate the _________________, and therefore the opportunity for individuals to ________________, and potentially secure direct reproductive opportunities.

Answer 26

• breading season
• number of broods
• stay at the natal nest

Question 27

what does a longer breeding season indicate

Answer 27

more time for social groups to form and yield associated benefits

Question 28

Nesting opportunities may also become increasingly scarce as the season progresses, further favoring staying at the natal nest — ___________________________________________________

Answer 28

potential interactions of nest-site limitation and temporal facilitation

Question 29

temporal facilitation - example

Answer 29

Some species of facultatively social halictid bees are solitary in more northern populations, and social in more southern populations.

Question 30

Social parasites ________________________ of other species for their own gain, often in the form of ______________________ of social species.

Answer 30

• exploit the social actions
• exploiting brood rearing

Question 31

Infiltration of a social parasite is achieved by __________________________ of the social species.

Answer 31

circumventing the guarding behavior

Question 32

Threat of parasitism may make offspring and/or nest _____________________________.

Answer 32

guarding critical for offspring survival

Question 33

parasitism - how does this impact costs and benefits

Answer 33

• inability for solitary individual to guard when foraging ↓c for individual that acts as a guard in a social group
• ↑b for reproductives in the social group

Question 34

Similar to the threat of parasitism, ____________________ pressure ___________________________ for better protection of offspring

Answer 34

• increased predation
• favors group formation

Question 35

_____________ pressure, and therefore high mortality of offspring reared by solitary parents, __________________ that help within a social group and ___________________.

Answer 35

• High predation
• ↓c for individuals
• adding defense to ↑b

Question 36

predation - example

Answer 36

• The cooperatively breeding cichlid fish (Neolamprologus pulcher).
• Experimental addition of predators reduces dispersal by helpers, increasing likelihood of social group formation.

Question 37

define synergistic social actions

Answer 37

When members of a group work together to complete actions that each acting alone simply could not complete

Question 38

Categories of synergistic benefits of sociality

Answer 38

• Assured fitness returns
• Access to novel resources that require social actions
• Division of labor, defined as a form of behavioral specialization within a social group

Question 39

Categories of synergistic benefits of sociality - assured fitness returns

Answer 39

even if you die, group membership provides some fitness gains (potentially direct and indirect)

Question 40

In all but clonal societies, ____________________ to potential offspring creates _____________

Answer 40

• differences in relatedness
• inherent conflict

Question 41

Ecological and synergistic benefits can tip the balance towards sociality, but ____________________________________.

Answer 41

conflict may remain as a destabilizing force

Question 42

what can further increase b and stabilize the social structure?

Answer 42

The evolution of reproductive traits and social tactics that increase conflict resolution

Question 43

define conflict resolution

Answer 43

• Reduction of group resources dedicated to conflict within the society
• OR the increase in group resources dedicated to cooperative offspring production.

Question 44

Conflict resolution traits and tactics generally _______________________________ for individuals to act on conflict.

Answer 44

reduce the information and opportunity