What is the adaptive value of parental care?

1. What is the adaptive value of parental care?

2. 6/12/08: Parental care Lecture objectives: • Be able to apply a cost-benefit approach to the evolution of parental behavior • Understand the factors that influence the evolution of adoption and brood parasitism • Be familiar with types of parental favoritism, and be able to predict when parent-offspring conflict might occur as well as its outcome

3. Parenthood, or taking care of offspring, is hard work Male Tamarins lose up to ____________ while carrying infants • Mother's love worth $117,000 per year, study says • Stay-at-home moms report working 94.4 hours per week

4. There are benefits and costs to parental care BenefitsImproved survival of offspringImproved quality of offspring Costs

5. Species vary in how much parental care is given Precocial: Altricial:

6. Variation in amount of parental care is explained by costs and benefits of care Hypothesis: birds adjust amount of parental care in relation to probability of survival Predictions: P1: N.A. more likely to care for offspring P2: S.A. more likely to care for self

7. Variation in amount of parental care is explained by costs and benefits of care Example: Nest defense by parent magpies

8. Species vary in which parent provides the majority of care Parental care in shorebirds

9. Parental care is generally provided by females… Why? Benefits greater for females Costs greater for males …but not always… Why? Waterbug Randall’s jawfish Stickleback

10. Paternal behavior might evolve when males can ensure paternity Hypothesis: Males are more likely to take care of young if they “think” they’re the dad

11. Paternal behavior might evolve when costs are lower for males than for females Do males pay a cost of parenting?Do females pay a cost of parenting?Which gender pays the larger cost?

12. To care for their young, parents must recognize their young Many colonial species are good at offspring recognition Mexican free-tailed bats Adoption in Emperor penguins

13. Juveniles sometimes seek adoption within their species Beg confidently Gulls So why do parents allow adoption? - Costs might be fairly low in some cases- Offspring recognition is imperfect:If you ignore the begging of a stranger, you might accidentally ignore your offspring

14. Parental deception: interspecific brood parasites Cowbird in eastern phoebe nest Common Cuckoo in reed warbler nest

15. Brood parasitism is common in cowbirds and cuckoos

16. Size (relative to host nestlings) influences a brood parasite’s success If hypothesis (above) is true, which chicks should have a higher survival?

17. Why accept a parasite’s egg?1. Cost-benefit approach Removing an egg might be ____________________ Costs of abandoning a nest might be _____ Hypothesis: Warblers will be more likely to incubate parasite eggs if there are few new nest sites available

18. Why accept a parasite’s egg?2. Mafia Hypothesis If a parasite finds that its offspring have been harmed, it will European great spotted cuckoo

19. Parental favoritism occurs when parents preferentially care for some offspring over others Hypothesis:Parent coots preferentially feed babies with more orange feathers

20. Some parents take favoritism to the extreme by allowing siblicide Great egret Brown boobie

21. Parent boobies can control siblicide to some extent Tendency to allow siblicide? Tendency to prevent siblicide? What do you predict if offspring are in control? If parents are in control? Masked booby(MB) Blue-footed booby(BFB)

22. Parent-offspring conflict occurs when the interests of parents and offspring are different Example: amount of food to feed offspring

23. Class discussion: parent-offspring conflict over siblicide (hypothetical example) 2 offspring, each will have 3 surviving babiesIf one bird commits siblicide, it will be able to have 5 surviving babies (but loses 3 nephews/nieces) r (parent – offspring) = 0.5r (uncle/aunt – niece/nephew) = 0.25r (parent – grandoffspring) = 0.25 • Is siblicide adaptive for the juvenile bird? (will siblicide increase its inclusive fitness?) • Is allowing siblicide adaptive for the parent bird?