Evolution of cooperative breeding in birds and mammals

1. Evolution of cooperative breeding in birds and mammals 報告者: 廖昱銓 呂翊維

2. Introduction • Cooperative breeding : adult individuals in addition to the genetic parents regularly aid in the rearing of young.

3. Introduction The two main questions in this chapter: • Why don’t helpers breed on their own? • Why do such individuals become helpers?

4. Diversity of cooperative breeding systems

5. Do helpers really help? Does helping have important fitness consequences for recipient breeders? Three majoy ways: • Increasing the success of breeding attempts. • Increasing the number of breedings per seasons. • Enhancing breeder survivorship.

6. Increasing the success of breeding attempts Univariate analyses -

7. Increasing the success of breeding attempts • White-fronted bee-eaters : covariate analyses The action of helpers really increasing fledging success. • Red-cockaded woodpeckers: multivariate analyses  The trend of increasing helpers number seen disappeared when including variance of age. other study  No influence of helpers was detected.

8. Increasing the success of breeding attempts • Experimental removal of helpers

9. Increasing the number of breedings per season • Grey-crowned babblers: Groups with many helpers renested more rapidly and reared more broods per season than did groups with fewer helpers.

10. Enhancing breeder survivorship • Breeder survival was higher with helpers. ex: Florida scrub jay, pied kingfisher, acorn woodpecker…..etc. • Longevity is proving lifetime fitness in birds and mammals, and increasing annual survivorship can have influence on lifetime productivity.

11. Why don’t helpers become independent breeders? • Routes to sociality

12. Why don’t helpers become independent breeders? The habitat saturation hypothesis for delayed dispersal: • shortage of breeding territoryauxiliaries aid breedersHelpers have possibility to become breeders in future. • Waitingis best done for helpers. The benefits of philopatry hypothesis for delayed dispersal: • unsaturated habitats  individuals still stay home and become helpers, because dispersal have more risk . • Benefits of stay home  1. inheritance 2. competition edge

13. Reconciling the difference

14. Reconciling the difference What might cause a steep gradient in the quality of breeding territories? 1. Limited by suitable breeding habitats. 2. Critical resource is distributed unevenly. 3. Occupants’ modification of habitats. 4. Labour force is critical for successful breeding.

15. A generalized constraints model of delayed dispersal • Shortage of mates • Prohibitive costs of independent reproduction

16. Tests of the constraints model Shortage of territory vacancies • Florida scrub jays Competition over territory vacancies • white-browed sparrow weavers • Power struggles?

17. Tests of the constraints model • Predicting the frequency of retention

18. Tests of the constraints model • Experimental tests 1. blue fairy wrens 2. Red-cockaded woodpecker • These experiments provide the strongest evidence to data of linked between delayed dispersal and constraint factor.

19. Why do helpers help? • Enhance its probability of survival. • Enhance its likelihood of becoming a breeder in the future. • Increase its fecundity when it does become a breeder. • Increase the production of non-descendent kin.

20. Enhance its probability of survival • Group size effects 1.Helping increases the number of young, which augments the size of helper’s group. 2.Vigilance or antipredator behaviour improves with increasing group size. • Resource effects 1.Helping is a payment to breeders to be allowed retain access to physical and social resources of the natal group.

21. Enhance its likelihood of becoming a breeder in the future • Shortage of suitable territories 1.Territorial inheritance 2. Coalition formation • Shortage of mates 1.Future mate acquisition

22. Territorial inheritance Through helping, the size of the group is enlarged ; the group then expands the size of its territory, which enables the helpers to bud off a portion of the natal area as its own breeding territory. • Coalition formation • 1.Larger coalitions have a competitive advantage over smaller one. 2.The act of helping is important to the formation of such coalition.

23. Future mate acquisition Helper demonstrates its parental abilities, thus enhancing the probability of being chosen as a mate by the original breeding female in a subsequent year.

24. Increase its fecundity when it does become a breeder • Gaining breeding experience Helping provides experience at parenting which translates into higher reproductive success when the helper becomes breeder. • Gaining future helpers Helping increases the likelihood that the helper will gain the services of the original recipients as it s own helper in the future.

25. Increase the production of non-descendent kin

26. Roles of mutualism, reciprocity and kin selection • Reciprocal altruism 1.One individual aids another 2.In anticipation that the recipient will return to the favor 3.Benefiting the actor at some time in the future

27. Importance of kinship • (WRA－WR)：the change of lifetime reproductive successof the recipient • (WAR－WA)：the change of lifetime reproductive successof the donor • rARy：therelatedness of A to R’s young • rAy： therelatedness of A to A’s young

28. Importance of kinship • Ik＞1 net cost to A’s personal reproduction. • Ik＜0 net cost to R’s personal reproduction. • 0 ＜ Ik ＜ 1 both direct and indirect benefits are occurring.

29. Thank you for your listening !!