Cooperative Breeding Flashcards
(9 cards)
How diverse are cooperative systems?
4-9% of bird species
3% of mammals
Described in >10 fish species
Social insects
Give some examples of helpers at the nest
Florida Scrub Jays:
- Have a breeding pair and 1.8 helpers on average
- Helpers feed and protect young from predators
- Helpers usually related to breeding pair (previous offspring)
Silver-Backed Jackels:
- Breeding pair and 1-3 helpers
- Helpers regurgitate food to pups and lactating female
Naked Mole-Rat:
- Very similar to eusocial insects
- Have a reproductive division of labour
What are plural breeders?
Several males and females share a nest and raise a communal brood
Banded Mongoose:
- 4-40 in a group
- Several females reproduce
Acorn Woodpecker:
- 2-14 in a group
- Often brothers and sisters
- 1-4 breeding males or females
- Up to 8 non-breeding helpers
What is the ecological constraint hypothesis for evolution of cooperative breeding?
Independent breeding is constrained in some way
Grown offspring delay dispersal and stay at home
Grown offspring help to rear later broods
What is the ecological constraint hypothesis assumption?
There is a better fitness return from breeding than helping - but breeding is constrained
What are the conclusions for the experimental evidence for the ecological constraint hypothesis?
Helpers are capable of reproduction
Habitat is limiting
Mates are limiting
How do helpers benefit from helping in cooperative breeding?
Direct fitness - fitness gained from personal reproduction
Indirect fitness - fitness gained from increasing production of non-descendant kin via kin selection
Give some direct fitness benefits of cooperative breeding
Increased survival:
- benefits of group living
- producing extra offspring benefits the helpers by increasing group size
- circumstantial evidence seen in banded mongoose who kidnap young from other groups for their own and cichlid fish more likely to accept immigrants when predation risk is high
Increased probabiluty of future breeding:
- territory inheritance (48% of florida scrub jay helpers eventually acquire all or part of parental territory)
- mate acquisition (secondary helpers not kin or distant kin and 41% of these inherited female when breeding male died in pied kingfishers)
Increased probability of future breeding:
- increased experience (skill hypothesis)
- Seychelles warbler - 1st breeders who had helped parents had more hatching success than those that didnt (although did not test to see if any genetic defects)
Give some indirect fitness benefits of cooperative breeding
Increased reproductive success of relatives - reproductive success tends to increase with number of helpers
Increased survival of related breeders = load-lightning. one or both parents reduce their efforts when assisted by helpers although improved parental survival is hard to demonstrate
