Lecture 13: Kin Selection Flashcards
Explaining behaviour on different levels
Proximate: Ontogeny, sensory development, triggers, learning
Ultimate: Phylogeny, fitness effects, coevolution -> Used by ecologists
Mechanisms and levels of selection
Natural selection
Sexual selection
Kin selection (Verwandtenselektion)
Kin selection in the origin of species by Darwin
-…selection may be applied to the family, as well as to the individual, and may thus gain the desired end. Breeders of cattle wish the flesh and fat to be well marbled together. An animal thus characterised has been slaughtered, but the breeder has gone with confidence to the same stock and has succeeded.“
-> nowadays it is known that “the family” and “stock” are genetically a kin group.
Natural selection on the individual level by Darwin
-Individual variation, partly heritable
-Limited Resources, competition
-Differential contribution of varieties to next generation
-Evolutionary change of a species
Consequence: Adaptation to an environment
Natural Selection on gene level by Richard Dawkins 1976
Variation: genes determine behaviour, in two or more alleles
Limited resources:
- competition among alleles
- co- operation among genes
Result: different numbers of offspring per allele
Consequence: Change in allele frequency in the population
Dawkins: „The Selfish Gene“ 1976
-Individuen nur als Vehikel der Genselektion
Got criticized for it
Co-operation:
-mutualism (both species benefit)
-altruism (a behaviour that benefits a recipient and has costs to the donor)
-nepotism (Vetternwirtschaft)
How can behaviours be explained, which are apparently detrimental to own fitness?
- siblicide (killing of siblings to increases own chances of survival)
- Infanticide (killing of offsprings (through parents))
Potential explanations for social behaviour
-kin selection
-group selection
-serves the survival of the species
-reciprocity
Inclusive fitness (Hamilton 1963, 1964 & Maynard Smith 1964)
Inclusive fitness (Gesamtfitness) = direct fitness + indirect fitness
-direct: offspring
-Indirect: Additional offspring of relatives, which are possible only through an investment of the focal individual
-Fitness value of the offspring depends on the relatedness (measured as index of relatedness (r))
Coefficient of relatedness
Hamiltons rule & Altruism
Altruism is favoured by natural selection when B/C > 1/r
Kin selection
Conditions for the increase of altruistic genes in a population:
Benefits (recipient) * r > Costs (donor)
r- Realtionship index
Cooperative breeding
Helpers postpone own reproduction or do not breed a second time
Cooperative breeding:
Long tailed tits by Russell & Hatchwell 2001
-Animals with failed broods help successful others to raise their broods
-Helpers are often relatives
Cooperative breeding:
Pied kingfisher (Reyer 1984) ??
three breeding tactics in he first year of life:
- delay breeding („delayers“) -> worst balance, no indirect fitness
-helping unrelated birds (secondary helpers) -> often (10/27) replace one of the parents they helped
- helping parents (primary helpers):
high effort: 3x more food than secondary
inclusivefitness is the highest
lower chance of survival to next year AND attract partner
Eusocial insects (Hymenoptera)
Darwin noticed this problem
Reproductive altruism:
- Potentially fertile workers abstain from producing their own offspring
-to help the queen (their mother) raising offspring (their sisters)
Haplodiploidy -> Females have higher kin (0.75 where human has 0.5)
workers remove eggs laid by other workers, because they are more related to the queen’s eggs than to the worker-laid eggs.
Other perspective: Superorganism -> extended phenotype from queen
Eusocial but diploid
-Termites
-Naked mole rats
-> to dangerous/environment is to harmful to just start new colony -> they increasing their fitness by helping sisters -> better to invest in indirect than in direct fitness because of ecological limits to direct fitness
related to mounds and burrows
Reciprocal altruism
- Blood sharing in vampire bats
- Hematophagic, forage at night, rest in communial roosts during day
- Share meals with animals that could not forage this night
**Conditions for reciprocity: ** - longevity, individual recognition, kin recognition
Test: share only with long known individuals (exchange experiments, Wilkinson 1984)… but theses are often related in nature
Reciprocal altruism: General conditions (Trivers 1972):
Long lived individuals
Stable groups
Individual recognistion
Exchange of donor and recipient role
Difference to mutualism: temporal delay
Arguments against Group selection
- Only genetic success counts: egoistic individuals (not regulating reproduction) have selective advantage over regulators
- Acting for the benefit of the group is not evolutionary stable
Examples:
-Proportion breeding, reproductive skew
-Density regulation by individuals
-Territoriality - Letting other benefit is only stable if
Reciprocity: long lived, kin recognition
Relatedness in the population: e.g. viscous populations with limited dispersal
ESS
Evolutionary stable strategies (Maynard-Smith u Price 1973)
ESS is a state of game dynamics where, in a very large population of competitors, another mutant strategy cannot successfully enter the population to disturb the existing dynamic (which itself depends on the population mix). Therefore, a successful strategy (with an ESS) must be both effective against competitors when it is rare – to enter the previous competing population, and successful when later in high proportion in the population – to defend itself. This in turn means that the strategy must be successful when it contends with others exactly like itself.
ESS- Hawk/Dove game
There will always be „hawks“ (that escalate fights and will gain a lot but may loose all) AND „doves“ (that are peaceful, win and loose very little) in a population, because both strategies have advantages. The proportion of hawks in a popualtion depends on the payoff matrix (quantifies costs ad benefits).
ESS- Sex ratio offspring
The ratio of males to female offspring ist 1:1 in most species. Why? – As soon as there are more of one sex it pays off to produce offspring of the other sex. It is evolutionary stable though to produce offspring of both sexes.
Group selection- Darwin 1871
(human) groups containing individual that behave social or altruistic have selective advantages in comparison to groups without such members
Group Selection- Wynne-Edwards 1962:
Animal societies controlling density…
-Mechanism: dominance, territoriality, aggressiveness…
Selection acts among societies with more or less good mechanisms to regulate reproduction
