Lecture 21: evolution of coop breeding Flashcards Preview

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Flashcards in Lecture 21: evolution of coop breeding Deck (18)
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1
Q

Cooperative breeding: Birds =

A

4-9% of species

2
Q

Cooperative breeding: Fish

A

20+ species

3
Q

Cooperative breeding: Mammals

A

3% of species

4
Q

Ecological constraints hypothesis

A

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
5
Q

Ecological constraints hypothesis explain cooperative breeding ____ species

A

WITHIN

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

6
Q

phylogeny & cooperative breeding

A

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
7
Q

hypothesis 1: Ecology constrains breeding birds

A
  • 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

8
Q

hypothesis 1: Ecology constrains breeding mammals

A

Lukas & Glutton-Brock 2017

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

9
Q

cooperative breeding evolves in unpredictable environments?

A

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

10
Q

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

A
  • 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
11
Q

constraint on dispersal =

A

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
12
Q

hypothesis 3: Life history hypothesis

A
  • 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
13
Q

slow life histories

A

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

14
Q

life history traits: slow vs short and tropical vs temperate

A

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

15
Q

hypothesis 4: cooperative breeding is associated with brood parasitism

A
  • 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)
16
Q

why is predicting sociality (cooperation) so difficult?

A
  • diverse social systems
  • diverse constraints (food,rainfall,tempted)
  • phylogeny, biogeography and life history traits covary (can’t pin point one thing your changing exactly)
17
Q

the debate over what factors drive social evolution

A

continues

18
Q

4 hypothesis to what drives social evolution (cooperation) :

A

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