Brood Parasitism

Question 1

What is brood parasitism?

Answer 1

A form of kleptoparasitism. They manipulate the host so they raise the young of the parasites, not their own.

Question 2

What species used brood parasitism?

Answer 2

Found amongst insects (Hymenoptera), fish and birds

Question 3

Give an example of brood parasitism.

Answer 3

Ants- enslaves its host which then provide labour and colony care for the parasite

Catfish- brood parasite of 2 such species. While these are spawning, the catfish eats some cichlid eggs (mouth brooder) and lays her own.

Question 4

What are the types of brood parasitism?

Answer 4

• obligative (generally can’t reproduce without hosts (can’t build nests/incubate))
• facultative (they don’t have to do it, only because it’s an advantage) ostrich, doves

Question 5

What are the benefits to the parasite?

Answer 5

It increases fecundity by removing the parental investment from parasite and places it on host.

= allows parasite to allocate more resources towards mating and reproduction

Question 6

What are the costs of parasitism to host

Answer 6

Loss of fecundity because of breeding failure.
- removal of host eggs by parasite or puncturing of host eggs
-eviction of host eggs by young parasite
- host abandons parasitised broods

Question 7

What type of interaction is brood parasitism?

Answer 7

Antagonistic- between species (parasite benefits at expense to host)

= strong selection pressure for hosts to evolve

= co evolutionary arms race

Question 8

What are some parasite strategies and host defences?

Answer 8

Mobbing
- sneaky layer
- distraction
- mimicry

Egg Recognition
- egg mimicry
- thick shelled eggs
- multiple laying (insurance against rejection)

Question 9

How do parasites match the colour of host eggs in egg mimicry?

Answer 9

• Deposit similar concentrations of colour pigment into their shells as host.
• Biliverdin
• Protoporphyrin IX
• Simple colour palette allows parasites to quickly evolve

Question 10

What are egg signatures?

Answer 10

An advanced form of defence by hosts against egg mimicry.

Each female in a host population will produce eggs that are distinctive to her- harder for parasites to copy

Question 11

What is a post hatch defence against parasites?

What are the responses to these?

Answer 11

A host may recognise parasite chick and not feed it

• early hatching (too big for host to remove)
• host egg/ chick removal
• chick mimicry
• nest abandonment

Question 12

Give an example of chick mimicry (1)

Answer 12

Pin-tailed whydah & Estreldid finch

• finch can detect parasitic whydah chicks and won’t feed them.
• whydah adapted mouth shape of finch

HOWEVER

• whydah can only mimic one species of finch and so each whydah has only 1 finch host and vice versa

Question 13

What must happen for post hatching discrimination to occur?

Answer 13

• Rates of parasitism must be sufficiently high to outweigh cost of mistakenly rejecting own chicks
• Hosts must have sufficiently high fecundity to compensate for mistakenly doing this

Question 14

How did brood parasitism evolve and why does it persist?

Answer 14

• Evolutionary lag hypothesis
• Evolutionary equilibrium hypothesis

Question 15

What is the evolutionary lag hypothesis?

Answer 15

Rejecting parasitism always better than accepting.

Hosts tend to accept because they’ve not yet evolved ability to defend against it

Question 16

What is retaliatory ‘mafia’ behaviour?

Answer 16

Parasites will destroy eggs or nestlings of hosts that eject parasitic eggs

Question 17

What is the evolutionary equilibrium hypothesis?

Answer 17

Hosts accept parasitism only because the cost associated with rejecting them is greater then cost of rearing them

(May mistakenly reject their own)