Parental Care/Family Conflict III

Question 1

What is the general idea behind asynchronous hatching in birds? What is the idea if synchronous hatching were to occur? What is an example (elaboration will be on another card)?

Answer 1

1. Asynchronous = parent brood reduction in case food is scarce
2. Synchronous = if food is scarce would increase aggression between sibs and decrease overall fitness of whole brood
3. Eurasian blackbirds

Question 2

Elaborate on the blackbird example of asynchronous and synchronous hatching. What experiment was done? What were the results? Why not use naturally occurring asynchronous broods?

Answer 2

1. Have synchronous and asynchronous broods during good and bad years (dry vs not dry because they eat worms)
2. Bad year = asynchronous does better, good year = synchronous does better (balanced competition for food, no one has age advantage)
3. Mom quality might decrease if she has to produce another brood

Question 3

What is genomic imprinting? What are maternally imprinted genes? What are paternally imprinted genes? How might these cause conflict conceptually (example on another card)?

Answer 3

1. Genes behave differently depending on the parent they come from
2. Gene expresses only in males
3. Gene expresses only in females
4. Paternal genes could demand more resources from mom than maternal genes because cost of finding resources is lower in paternal genes

Question 4

What is an example of a species with an imprinted gene? What is the gene called? What does it do? How does it effect mice?

Answer 4

1. Mice
2. Igf2
3. Insulin-like growth factor is paternally imprinted (only expressed if dad gives it to you).
4. Deactivate the paternal allele –> 60% of normal body weight in young (no effect if maternal allele is KOed)

Question 5

What is the counter to Igf2? What is this an example of? How does it effect mice? How does this conflict with Igf2?

Answer 5

1. Igf2-receptor (maternally imprinted)
2. Red queen
3. Inactivate maternal allele –> 20% increased body weight
4. Igf2 increases offspring body weight but that increases hardship on mom, so igf2r keeps them from getting too big.

Question 6

What are examples of conflict resolution between parent and offspring (and consequent results if experiments were done) (4, two are the same species)? What supports the fact that begging is an honest signal?

Answer 6

1. Begging handicap signal - Parents need honest signals of needing food, so need more food = beg louder - Canaries
2. Great tits - tested intensity of begging over time (60 and 150 mins) and original field parents using playbacks (high vs low rates) - Mom responds to intensity regardless of whose kids she’s taking care of
3. Burying beetles - Moms feed correlating with genetic offspring begging level even when fostering (genetic basis? dunno).
4. Canaries –> androgens –> chicks (more food for mom = more androgens = epigenetics in offspring)
5. Offspring beg too much = extra energy spent not matched by parent, offspring beg too little = not fed enough

Question 7

What is a brood parasite? What are three examples of workarounds to conflict resolution between parent and offspring exhibited by brood parasites?

Answer 7

1. Skew food delivery to themselves by tossing siblings out (they invade the nest)
2. Brown headed cowbirds –> don’t toss “sibs” out of nest (instead grows faster = stronger signal = increase feeding rate)
3. Cuckoos –> bigger mouth and high begging rate that tosses host into action (supernormal stimulus since it does toss its “sibs”)
4. Horsfields hawk cuckoo –> wing patch that mimics gaping display of fairy wren (parent increases feeding rate for these wings compared to solid ones)