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tarantula hawk red shouldered hawk emperor penguin Parental care Very costly behavior - time - energy - vulnerable to predation earwig

Sibling conflict Sibling aggression and siblicide Occurs when resources are variable or in short supply? Offspring compete for resources (they only share 50% of genes)

Galapagos masked booby have two eggs, first hatched chick always kills second chick blue-footed booby have two eggs, often raise two young

Parent offspring conflict (Trivers) Selection may act on parents and offspring differently. Some actions that increase fitness of offspring may reduce fitness of parents.

Parental favoritism Likely occurs when resources are variable and adults have more young than they can raise (bet hedging) Females can invest in eggs differently (even choose sex in some species). Young can be fed preferentially. Seychelles warbler

Parental favoritism Honest signals of quality in offspring? barn swallows

Asynchrony in hatching (birth order) can promote or reduce sibling conflict and parental favoritism great egret

Can parents control sex of offspring? Seychelles Warbler

Can parents control sex of offspring? Haplo / diploid organisms (like ants, bees and wasps) fertilized egg = female ; un-fertilized egg = male Temperature Dependant Sex Determination (TSD) many reptiles

Helpers at the nest In some animals, juveniles stay to help second nesting effort. More often female juveniles. Both direct and indirect benefits. Direct (learning about maternal care) Indirect (inclusive fitness by helping rear related offspring magpie jays voles

Helpers at the nest Leads to overlapping generations Key step in the evolution of sociality?

Genetics basis for mating systems / parental care. prairie voles Monogamous, male parental care meadow voles polygynous, no male parental care

In male prairie voles, vasopressin and dopamine in the forebrain regulate affiliation between mates (bond formation). Vasopressin receptor is expressed at higher levels in monogamous species than polygynous species. Lim and colleagues, used a viral vector to transfer the vasopressin receptor gene from the monogamous species into the polygynous species. With this change in a single gene, the polygynous species essentially became monogamous.