conflict within social groups: Flashcards
what is social behaviour -
Group living -> social groups
- Parental behaviour in families
- Helping behaviour in extended families
- Cooperation in flocks / herds / social groups
Benefits of living in groups -
- Greater protection from predators (dilution effect + increased vigilance)
- Enhances obtaining, locating or maintaining resources.
- Creates mating opportunities
- Reduces probability of infanticide (mammals)
Costs of living in groups -
- Increased competition
for mates, resources (e.g. nest sites) - Increased conspicuousness to predators
- Increased chance of disease transmission
kin selection -
helping individuals that share your genes
Parental care is altruistic – caring for young is costly
Parents almost always care for their own young.
Kin Selection / Inclusive Fitness - Hamilton’s rule…
Relatedness x Benefit > Cost
altruism (benefits others at cost to itself) will evolve if the benefit of the behavior received by the recipient multiplied by the relatedness of the recipient to the donor is greater than the cost of the behavior to the donor
Conflict with families -
- conflict between male an female parents over who should invest
- Parent-offspring conflict (supply and demand of investment)
- Sibling conflict (sibling rivalry)
- Conflict in social insect societies (still a family)
interbrood conflict -
current offspring vs. future offspring
leads to faculatative siblicide
e. g. in sea lions when offspring have no older siblings they are more likely to survive = older siblings take all resources from mother and can kill their competitor
e. g. blue footed boobies lay two eggs 4 days apart, the older sibling begs more efficiently so if food is scarce the older sibling takes the food and the younger starves
faculatative siblicide =
siblings end up being killed dependent on environmental conditions
Obligate siblicide =
- in some birds of prey, pelicans and boobies - the older sibling always kills the younger sibling.
- Second egg is as insurance
- Experimental removal of second egg decreases reproductive success.
Sibling rivalry is determined by…
by benefit/cost ratio, but also by relatedness
e.g Begging behaviour in passerine birds – loudness increases as relatedness in the nest declines
Types of conflict within social insect societies:
- Male parentage (who produces males: queens or workers?)
- Sex ratio (investment into females and males – queens and males)
- Reproductive skew - the sharing of reproduction between queens
- Caste fate – whether a female becomes a queen or a worker
in social insect nests with one singly mated queen…
- the queen can lay haploid eggs which become male (0.5 relatedness to queen)
- the queen can also mate with one male and keep sperm in her body to produce diploid eggs which become workers or queens (0.5 relatedness to queen and 0.75 relatedness to each other due to having the same father)
- the queens haploid eggs are related by 0.25 to the queen’s diploid eggs
- workers can also lay haploid eggs which will develop into males (0.5 relatedness to mother and 0.375 relatedness to aunts)
- workers are more closely related to the male sons of their sister workers (0.375) than to their brothers (0.25)
in social insect nests with one multiply mated queen…
- this only reduces the relatedness between workers as they have different fathers
- workers more closely related to their brothers (0.25) than to the sons of their sister workers
Conflict over male Parentage in social insect - Nests with one singly mated queen…
- worker sons = 0.5 relatedness to queen
- worker nephews (sons of sister workers) = 0.375 relatedness to aunt
- worker brothers (haploid sons of the queen) = 0.25 relatedness to sister workers
= workers have a preference to care for their own sons, then their nephew and then their brothers
= workers produce males
Conflict over male Parentage in social insect - Nests with one multiply mated queen…
- worker sons = 0.5 relatedness to queen
- workers more closely related to their brothers (0.25) than to the sons of their sister workers
= workers have a preference to care for their own sons, then their brothers and then their nephews
= worker policing behavior (workers prevent each other from laying eggs, e.g. honey bee workers eat other workers eggs)
= queen produces males
