13: brood parasitism

Question 1

what do brood parasites parasitize?

Answer 1

the parental care of their hosts

Question 2

what do intraspecific parasites often do?

Answer 2

lay eggs in clutches of conspecifics

Question 3

list 5 examples of intraspecific brood parasites

Answer 3

• european starling
• burying beetle
• cliff swallow
• masked weaver
• american coot

Question 4

give 3 points about the masked weaver bird as a brood parasite

Answer 4

• breed in large colonies
• 23-35% rate of parasitism
• egg divergence and recognition

Question 5

lyon 2003 studied the american coot- give points about what was found (4)

Answer 5

• 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

Question 6

what do interspecific brood parasites often do?

Answer 6

lay eggs in clutches of one or more host species

Question 7

list 3 interspecific brood parasites

Answer 7

• cuckoo catfish
• pin tailed whydah
• cuckoo

Question 8

how does the cuckoo catfish parasitise?

Answer 8

parasitises cichlid

• will deposit eggs when the cichlid spawns
• once cuckoo catfish egg hatches it will eat the cichlid eggs

Question 9

how many and what % of bird species are interspecific brood parasites?

Answer 9

100

1%

Question 10

what is a coevolutionary arms race, such as the one between the cuckoo and its host?

Answer 10

host defences select for adaptations in the parasite resulting in counter adaptations from the host

Question 11

in a coevolutionary arms race what may it reach or what may it remain?

Answer 11

reach evolutionary equilibrium

remain evolutionary dynamic

Question 12

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

Answer 12

a) 10
b) 15-20
c) one host species
d) mimetic egg

Question 13

how is gene flow likely maintained in the cuckoo?

Answer 13

males show no specialisation

Question 14

what are those that specialise on a particular host species referred to as?

Answer 14

gens/gentes

Question 15

what does parasitism result in for the host?

Answer 15

zero reproductive success

Question 16

what leads to host defences from brood parasitism and what leads to brood parasitism from host defences?

Answer 16

adaptation

counter adaptation

Question 17

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?

Answer 17

if laid before host lays its eggs 100% rejected but if laid after then 0% rejected

Question 18

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?

Answer 18

if egg placed in the morning then 50% rejected whereas in the afternoon 0% rejected

Question 19

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?

Answer 19

if stuffed cuckoo and egg placed then 45% rejected but if just the egg laid then 0% rejected
- so better to lay quickly

Question 20

in a davies and brooke experiment involving placing model cuckoo eggs in reed warbler nests what was found for: the size of egg laid?

Answer 20

if a large egg of 10g placed then 40% rejected but if a small egg of 3.4g laid then 0% rejected

Question 21

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?

Answer 21

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%

Question 22

in a davies and brooke experiment was was the conclusion?

Answer 22

cuckoos have evolved mimetic eggs and egg laying behaviour in response to host defences

Question 23

following on from davies and brookes experiment how did they answer the question: have hosts evolved in response to cuckoos?

Answer 23

• 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

Question 24

compare the rejection in the UK and iceland for the meadow pipit and pied wagtail and explain why

Answer 24

meadow pipit: UK= 56%, iceland= 17%
pied wagtail: UK= 71%, iceland= 20%
- in iceland there are hosts but no cuckoos so rejection is lower

Question 25

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

Answer 25

a) 94%
b) 67%
c) 0%

Question 26

what has parasitism selected for?

Answer 26

egg rejection

Question 27

what does the cuckoo finch parasitise and what % are parasitised?

Answer 27

tawny flanked prinia

20%

Question 28

what did spottiswoode and stevens find for the evolution of parasite and host egg patterning and colouration 2012? (5)

Answer 28

• 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

Question 29

what are the 4 sequences of events for a snapshot of a continuing evolutionary arms race?

Answer 29

1. before parasitism no rejection
2. parasitism favours rejection
3. evolution of mimicry by the parasite and specialisation results in gentes
4. host defences win and if no parasitism then host defences weaken

Question 30

as the number of generations needed for the rejection gene to spread decreases what happens to the % nests parasitised?

Answer 30

decreases

Question 31

give 3 points about the brown headed cowbird

Answer 31

• generalist with 216 hosts
• no mimicry
• > 50% hosts parasitised

Question 32

why may rejection not always occur? (6)

Answer 32

• 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

Question 33

the outcome of the arms race is variable - what does it depend on

Answer 33

many factors including frequency of virulence of parasitism