13: brood parasitism Flashcards
what do brood parasites parasitize?
the parental care of their hosts
what do intraspecific parasites often do?
lay eggs in clutches of conspecifics
list 5 examples of intraspecific brood parasites
- european starling
- burying beetle
- cliff swallow
- masked weaver
- american coot
give 3 points about the masked weaver bird as a brood parasite
- breed in large colonies
- 23-35% rate of parasitism
- egg divergence and recognition
lyon 2003 studied the american coot- give points about what was found (4)
- 41% pairs parasitised
- 43% hosts reject at least one parasitic egg
- colour ranked eggs in terms of markings
- will reject eggs that are different from their own
what do interspecific brood parasites often do?
lay eggs in clutches of one or more host species
list 3 interspecific brood parasites
- cuckoo catfish
- pin tailed whydah
- cuckoo
how does the cuckoo catfish parasitise?
parasitises cichlid
- will deposit eggs when the cichlid spawns
- once cuckoo catfish egg hatches it will eat the cichlid eggs
how many and what % of bird species are interspecific brood parasites?
100
1%
what is a coevolutionary arms race, such as the one between the cuckoo and its host?
host defences select for adaptations in the parasite resulting in counter adaptations from the host
in a coevolutionary arms race what may it reach or what may it remain?
reach evolutionary equilibrium
remain evolutionary dynamic
in the cuckoo
a) how many main host species in europe
b) how many eggs do females lay per season
c) what do females specialise on?
d) what is usually laid
a) 10
b) 15-20
c) one host species
d) mimetic egg
how is gene flow likely maintained in the cuckoo?
males show no specialisation
what are those that specialise on a particular host species referred to as?
gens/gentes
what does parasitism result in for the host?
zero reproductive success
what leads to host defences from brood parasitism and what leads to brood parasitism from host defences?
adaptation
counter adaptation
in a davies and brooke experiment involving placing model cuckoo eggs in reed warbler nests what was found for: when the eggs were often laid in relation to the host?
if laid before host lays its eggs 100% rejected but if laid after then 0% rejected
in a davies and brooke experiment involving placing model cuckoo eggs in reed warbler nests what was found for: what time of day the eggs were laid?
if egg placed in the morning then 50% rejected whereas in the afternoon 0% rejected
in a davies and brooke experiment involving placing model cuckoo eggs in reed warbler nests what was found for: the speed at which eggs are laid?
if stuffed cuckoo and egg placed then 45% rejected but if just the egg laid then 0% rejected
- so better to lay quickly
in a davies and brooke experiment involving placing model cuckoo eggs in reed warbler nests what was found for: the size of egg laid?
if a large egg of 10g placed then 40% rejected but if a small egg of 3.4g laid then 0% rejected
in a davies and brooke experiment involving placing model cuckoo eggs in reed warbler nests what was found for: why a mimetic egg is laid?
results for if each gen’s egg was placed in the nest:
- pied wagtail: 81% rejected
- redstart type: 70% rejected
- meadow pipit: 44%
- reed warbler: 0%
in a davies and brooke experiment was was the conclusion?
cuckoos have evolved mimetic eggs and egg laying behaviour in response to host defences
following on from davies and brookes experiment how did they answer the question: have hosts evolved in response to cuckoos?
- placed non mimetic model eggs in nests of 13 suitable hosts or 9 unsuitable hosts
- found that rejection has only evolved in the parasitised species
compare the rejection in the UK and iceland for the meadow pipit and pied wagtail and explain why
meadow pipit: UK= 56%, iceland= 17%
pied wagtail: UK= 71%, iceland= 20%
- in iceland there are hosts but no cuckoos so rejection is lower
in spain and sweden hosts have variable exposure to parasites- what % of non mimetic eggs were rejected in each case:
a) ancient sympatry
b) recent sympatry
c) allopatry
a) 94%
b) 67%
c) 0%
what has parasitism selected for?
egg rejection
what does the cuckoo finch parasitise and what % are parasitised?
tawny flanked prinia
20%
what did spottiswoode and stevens find for the evolution of parasite and host egg patterning and colouration 2012? (5)
- prinia has more diverse egg polymorphism than any other bird
- hosts use several aspects of parasitic egg appearance to reject foreign eggs
- over time both host and parasite eggs have become more diverse
- more of a shift to blue for the gg colour
- the parasites have tracked the host eggs
what are the 4 sequences of events for a snapshot of a continuing evolutionary arms race?
- before parasitism no rejection
- parasitism favours rejection
- evolution of mimicry by the parasite and specialisation results in gentes
- host defences win and if no parasitism then host defences weaken
as the number of generations needed for the rejection gene to spread decreases what happens to the % nests parasitised?
decreases
give 3 points about the brown headed cowbird
- generalist with 216 hosts
- no mimicry
- > 50% hosts parasitised
why may rejection not always occur? (6)
- costly
- recognition errors where own eggs are rejected
- ejection costs cause damage to own eggs
- northern oriole causes 0.26 damage to its own eggs when rejecting others
- nest defence
- common grackle is good at guarding
the outcome of the arms race is variable - what does it depend on
many factors including frequency of virulence of parasitism
