Brood parasitism Flashcards
Define intraspecific brood parasites and give examples
→ lay eggs in clutches of conspecifics
E.g European starling, Burying beetle
= has to be cryptic
Define interspecific brood parasites + examples
→ lay eggs in clutches of one or more host species (different to own)
e.g Cuckoo catfish, waxbill, cichlid
What egg-related adaptations do cuckoos have to enable their brood parasitism?
- Lays more eggs per season
- Lays small eggs v quickly
- Lays eggs in afternoon
- Removes one host egg when she lays
- Mimetic eggs
- Eggs hatch quicker than hosts (bc incubated for longer)
Describe the findings of Davies & Brooke’s study on cuckoos evolved adaptations
- Q: Have cuckoos evolved in response to hosts?
- R: Yes e.g egg laying behaviours, mimetic eggs
- C: cuckoos have evolved in response to host defences, but host defences have also only evolved in response to parasitisation
How do Prinias use egg polymorphism in response to parasitisation?
(Spottiswoode & Stevens, 2012)
- Has more diverse egg polymorphism than any other birds
- They use this to reject foreign eggs
How can Prinia eggs be seen to be changing over time? and cuckoo eggs?
(Spottiswoode & Stevens, 2012)
- Prinia eggs are diversifiying in colour
- But, so are cuckoo eggs
Describe the expected evolutionary sequence of mimicry and defences
(4 points)
-
Before parasitism → no rejection
Unsuitable hosts / host in allopatry -
Parasitism → selection favours rejection
Depends on parasitism rate
High rate = evolution favours defences
Low rate = no selection for defensive behaviour e.g Dunnocks vs cuckoo -
Evolution of mimicry by parasite (to overcome host defences)
Specilasation = gentes -
Host defences ‘win’
No parasitim, so host defences weaken again, cycle repeats
What the the costs of host defence behaviours?
- Recognition errors (eject own eggs)
- Ejection costs (damage own eggs)
= Selection pressure against rejection
