Case study: Coop breeding in long-tailed tits Flashcards
their cooperative breeding system:
- non breeding season: live in flocks (6-20 birds) copied of kin and non-kin
- in march: all birds breed in pairs independently (1:1 sex ratio)
-female lays about 10 eggs - nests suffer high rate of predation 75% r destroyed
- when nest destroyed, birds can try again and breed, abandon breeding, become helpers (common males, 50% of broods have helpers [1-8])
HATCHWELL ET AL 2004 - depends on time of year of nest failure: failure after 10th may don’t try and breed again, before this they may try again
fitness benefits of helping for the long tailed tits: INDIRECT BENEFITS
- HELPING RELATIVES
- 77% help close kin, usually a sibling, often male (helping nieces/nephews at a brood)
- Is an ACTIVE choice shown by RUSSELL AND HATCHWELL 2001, failed breeder choose kin over non-kin
- 16/17 chose rel, no diff in distance from original nest
- Helpers also work harder for closer kin NAM ET AL 2010
- HATCHWELL ET AL 2014 surviving fledgling to become a breeder, those with helpers are more likely to survive
- original breeders also more successful in future yrs as well, males w helpers do less work
fitness benefits of helping for the long tailed tits: DIRECT
- Few f helpers, don’t lay eggs in other birds nests
- M gain no extra pair paternity
- FUTURE BENEFITS?
- enhance winter survival? gain breeding experience? future mates? future help?
- helpers in following year greater survival than non helpers? NO
–NOT WORTH HELPING NON KIN, no direct benefits
Hamilton’s Rule in helpers in long tailed tits:
HATCHWELL ET AL 2014
- COSTS: opportunity cost; helpers don’t lose anything by helping, SURVIVAL COST; helpers survival is less than that of non-helpers (–> so helping is altruistic)
- BENEFITS: productivity; help add to productivity of the pair, breeding male load lightened
- RELATEDNESS: pedigree/genotyping
- rB>C? BUT YES IT IS SATISFIED
Processes generating kin structure in long tailed tit populations
(so kin is available to go help other kin)
- limited dispersal for M&F majority under 800m
- coordinated dispersal of kin: when they do disperse, they disperse together (discovered by analysing migrants relations)
(SHARP ET AL 2008)
(-ESTONIA:
long tailed tits migrate a lot, in they travel with relatives)
-small effective population size: low nest success, high recruitment
effective population size
proportion of population that contribute genes to next generation
-humans as most reproduce so they have a large effective population size
infraspecific evidence: look at constraints driving cooperation:
- experiments
- or long term study you can compare cooperation across many years
long tailed tits: constraints driving cooperation: long term study comparing coop
HATCHWELL ET AL 2013
1) nest predation rate (40-80%)
- -does variation in predation rate affect helper numbers, YES (peaked graph nest predation rate vs proportion of pop that help)
2) Length of the breeding system: longer breeding season, less number of helpers, as they have opportunity to breed again for themselves
Emlen 1982 model in relation to long tailed tits
Limited opportunity for successful independent breeding is CONSTRAINED by nest predation and short breeding systems
–failed breeder living in close proximity to kin IS CONSTRAINED BY kin selected fitness gains —> failed breeder help to rear related broods
long tailed tit have a __ selected cooperative breeding system, with active __ discrimination
KIN
the indirect and direct components of inclusive fitness can be quantified and __ rule is satisfied
Hamiltons
population kin structure raises from
limited, coordinated dispersal and life history traits
what constrains independent breeding
nest predation and short seasons
