KIN SELECTION, PARENTAL CARE AND ALTRUISM The evolution of social behaviour in animals

1. KIN SELECTION, PARENTAL CARE AND ALTRUISM The evolution of social behaviour in animals

2. SELFISH BEHAVIOUR, ALTRUISM, KIN SELECTION 1. Selfishness increases a gene's fitness at the expense of another. Altruism increases another gene's fitness at the expense of its own. 2. Helping a related individual is kin-altruism - a gene helps copies of its own genes in other individuals and so improves its own fitness. Inclusive Fitness is the relative reproductive success of a gene in an individual PLUS all the close relatives. Kin Selection is the process selecting for adaptations that benefit close relatives.

3. HAMILTON’S RULE 3. Hamilton’s rule Kin altruism evolves when the benefit (b) from helping a relative, reduced by the degree of relatedness (r), is greater than the cost (c) to the helper. b * r > c The classic example is Parental care

4. PARENTAL CARE 4. Parental Care evolves by Kin Selection. More common than Sibling Care because the degree of certainty of genetic relatedness is greater between parent-offspring than between siblings. 5. Conflict of the sexes: In Parental Care the sexes invest different amounts in their offspring and there is a conflict of interest.

5. PARENTAL CARE BENEFITS – Conflict of the generations 6. Trivers (1972) defines Parental Investment as "any investment by the parent in an individual offspring that increases the offspring's chances of surviving (and hence reproductive success) at the cost of the parents' ability to invest in other offspring". 7. There is a period of conflict of interest between mother and offspring, when it benefits the mother to stop care but benefits the offspring to continue.

6. EUSOCIAL BEHAVIOUR 8. Eusocial behavior is the cooperation of individuals in a group to raise young. Its features are: i) reproductive division of labour, ii) overlap of generations, iii) cooperative care of young. Examples are 1. Eusocial hymenoptera – ants, some bees & wasps with sibling care 2. Cooperative breeding in birds 3. Human grandmothers

7. SIBLING CARE 9. Hymenoptera show sibling care. Evolved because sisters are more closely related than mother-offspring.

8. COOPERATIVE BREEDING • 10. Co-operative breeding - evolves if a) resources are scarce • and b) remain so for long periods. e.g. in tropics. • Then require several helpers to raise young. • Examples are seen in birds. Sibling helper birds obtain • two advantages: • learn parental care while helping, • b) promote their own genes in their younger siblings • (kin altruism).