Lecture 21: evolution of coop breeding

Question 1

Cooperative breeding: Birds =

Answer 1

4-9% of species

Question 2

Cooperative breeding: Fish

Answer 2

20+ species

Question 3

Cooperative breeding: Mammals

Answer 3

3% of species

Question 4

Ecological constraints hypothesis

Answer 4

Emlen 1982

-coop breeding evolves through 2 steps

• -independent breeding is constrained –> habitat saturation/ecological constraints)
• -grown offspring delay dispersal and “stay at home”
• -grown offspring help to rear later broods
• exp evidence, red constraints = red help
• –sociable weaver Covas et al 2004

Question 5

Ecological constraints hypothesis explain cooperative breeding ____ species

Answer 5

WITHIN

— but y don’t non-breeders help in all species?

Question 6

phylogeny & cooperative breeding

Answer 6

there is a strong phylogenetic component to cooperative breeding

• evolved in some lineages but not others
• -strong phylogenetic tree for birds, hence y its useful

Question 7

hypothesis 1: Ecology constrains breeding birds

Answer 7

• African Starlings (45 spp.)
• some coop, some not
• classify habitat (savannah/non savannah)
• found coop associated w particular habitat, all in savannah hab (non coop mostly non savannah)
• sav habitats less predictable (rainfall)

& a global example (temp variation and rainfall years of environments across globe), coop associated w variation in rainfall

Question 8

hypothesis 1: Ecology constrains breeding mammals

Answer 8

Lukas & Glutton-Brock 2017

- Global study rainfall and temp, coop seen highest in areas of variation

Question 9

cooperative breeding evolves in unpredictable environments?

Answer 9

Evidence not conclusive, OR does cooperative breeding allow colonisation of harsh environments

Question 10

hypothesis 2: benefits of philopatry (staying at home) select for delayed dispersal

Answer 10

• Dickinson & McGowan
• Western Bluebirds
• sons usually spend the winter on their natural territory, & may help in following year
• mistletoe is key resource (disrupt this how much)
• more sons stayed when mistletoe removed

Question 11

constraint on dispersal =

Answer 11

benefit of staying

• • different sides of the sam coin
• equal each other
• the ecological constraints hypothesis & benefits of philopatry hypothesis differ only in the emphasis places on the process and cons of staying/leaving

Question 12

hypothesis 3: Life history hypothesis

Answer 12

• life history traits predispose some lineages to cooperate
• • slow life histories reduce rate at which breed gin vacancies arise
• • more likely for offspring to delay dispersal and stay at home
• -> looked at longevity, clutch size and migratory etc
• -SPECIES W SLOW LIFE HISTORIES = COOPERATIVE UNDER CERTAIN ECOLOGICAL CONDITIONS, short-lived large clutches never cooperate whatever the conditions
• HORNBILLS

Question 13

slow life histories

Answer 13

(life long time breed quite a bit, small clutch sizes) invest a lot in breeding

Question 14

life history traits: slow vs short and tropical vs temperate

Answer 14

slow = tropical
short = temperate
—-> so is it not just a correlate?

Question 15

hypothesis 4: cooperative breeding is associated with brood parasitism

Answer 15

• superb fairy wren is parasitised by Horsfields bronze cuckoo
• cuckoo makes sense y pick cooperative species (more food) (chicks heavier more likely to fledge)
• superb fairy wren pick coop as better defence to parasitism (less parasitism found in larger groups)
• global distributions of brood parasitism and coop match, direction of association is uncertain tho (who picked who)

Question 16

why is predicting sociality (cooperation) so difficult?

Answer 16

• diverse social systems
• diverse constraints (food,rainfall,tempted)
• phylogeny, biogeography and life history traits covary (can’t pin point one thing your changing exactly)

Question 17

the debate over what factors drive social evolution

Answer 17

continues

Question 18

4 hypothesis to what drives social evolution (cooperation) :

Answer 18

1) cooperative breeding is associated with brood parasitism
2) Life history hypothesis
3) Ecology constrains breeding birds
4) benefits of philopatry (staying at home) select for delayed dispersal