Week 4, part 5- Cryptic female choice. Flashcards
Why is the term cryptic used?
Cryptic is used because it is difficult to see (to study), we did not necessarily know it was happening.
Postcopulatory sexual selection:
What is sperm competition equivalent to?
Sperm competition is the postcopulatory equivalent of precopulatory male-male competition (i.e. a form of intrasexual selection).
Cryptic female choice:
What is it?
Who coined the term cryptic and when?
It is the ability of females to favour one male over another - after initiation of copulation.
Randy Thornhill in his study of scorpion flies.
Continuation from cryptic female choice:
Why is it called cryptic?
Explain it all.
Does it depend on various behavioural, morphological and physiological traits?
Can females exert choice through a range of different mechanisms?
Because it is hidden from researchers who only study male mating success.
Looking at which males is getting the most matings is easy to study but if you wanted to see which male is successfully fertilising the most eggs, this would have been difficult to spot before DNA fingerprinting technology came out.
Yes.
Yes.
For insects like male scorpion flies, what does how much sperm transferred during copulation depend on?
What does it essentially determine?
What do the females choose?
Why is it called postcopulatory? Explain.
The size of the nuptial gift.
How many eggs the male gets to fertilise.
The females choose the males who bring the biggest gift. Those males will fertilise a large number of their eggs.
Called postcopulatory because the decision is after copulation starts, they are stop copulation early when the gift is not big and they are letting it go on when the gift is large.
Scorpionfly Harpobittacus nigriceps:
What do females in this species do?
Based on the characteristic of the male, do they decide how many eggs to lay?
Are there a lot of mechanisms females can use to exert choice during postcopulatory sexual selection?
Females lay significantly more eggs in the first 10 hours after copulating with a large male than a smaller male.
Yes.
Yes.
Mechanisms of cryptic female choice:
What is the first one?
Explain it using insects.
Premature interruption of copulation.
In the case of insect species where sperm transfer is continuous, they can decide when to stop copulation and by stopping it early they can reduce the number of eggs that is fertilised by a particular male.
Mechanisms of cryptic female choice:
What is the second one?
Explain it.
Denial of deeper genital access.
In some species, their genitals are complex and the males have to put the sperm somewhere deep inside the female for them to have a chance to fertilise their eggs, the females can control access to those deeper parts of their reproductive system.
Mechanisms of cryptic female choice:
What is the third mechanism?
Explain it- Use an example.
What can females essentially do?
Lack of sperm transport or storage.
In some species, the females have to actively transfer or pump the sperm to a storage place.
Like in rats, when the male deposit sperm into a female, her uterus sucks it up to be used to fertilise her eggs but if she quickly mates with another male, this process is interrupted and does not happen.
Females can through lack of sperm transport bias success towards some males than other males.
Mechanisms of cryptic female choice:
What is the fourth mechanism?
Explain it.
Give an example of an animal which does this.
Discharge or digestion of male sperm.
Females can discharge sperm from undesirable males.
Chickens- they can dump the sperm of undesirable males.
Mechanisms of cryptic female choice:
What is the fifth mechanism?
Give an example.
What is the sixth mechanism?
Explain it.
Rejection or removal of mating plugs- this is after the male is gone- for example, the female rats eat the plugs we were shown previously.
Prevention of plug removal by subsequent males- other males might come along and try to remove the plugs and females can stop this from happening.
Mechanisms of cryptic female choice:
What is the seventh mechanism?
Is this important?
Give an example with insects.
Why is this postcopulatory?
Lack of rejection of advances by subsequent males.
Yes.
Insects with last male precedence- If she mated with a male but finds him undesirable she can mate with another male and bias things against the first male. The second male will get all the fertilisation success.
Because the first copulation has already happened- if she does not do anything, the first male is going to fertilise all her eggs, she has to take action to prevent this if he is undesirable.
Mechanisms of cryptic female choice:
What is the eight mechanism?
Explain it.
What is the ninth mechanism?
Explain it.
Selective use of spermatophores.
The spermatophore gets attached to the outside of the female, the females can choose which spermatophore to use.
Selective use of stored sperm.
They can selectively use the sperm that they have stored from different males- dung flies do this.
Mechanisms of cryptic female choice:
What is the tenth mechanism?
What is the 11th mechanism?
Explain it.
Making remating difficult.
Selective fusion with sperm that reach egg.
Their eggs could refuse to accept certain types of sperm- not much evidence.
Mechanisms of cryptic female choice:
What is the 12th mechanism?
Explain it.
Lack of ovulation/ovieposition.
In some species there are induced ovulators (they only ovulate after mating has happened). Females can adjust whether or not they ovulate or lay eggs depending on what the male was like.
Mechanisms of cryptic female choice:
What is the 13th mechanism?
Explain.
What is the 14th mechanism?
Lack of preparation of uterus for implantation.
Go more down the process- Imagine a mammal and the egg is fertilised and is floating around the fallopian tube- females uterus could refuse to accept the fertilised for implantation.
Abortion- In some species, the females can end pregnancies (reabsorb them).
Mechanisms of cryptic female choice:
What is the 15th mechanism?
Explain it.
What is the last mechanism?
Failure to invest maximally in mate’s offspring.
Postcopulatory choice can extend to after the offspring are hatched or born- a female could decide not to invest in offspring fathered by one male rather than another male.
Not rejecting advances by subsequent males.
Selective use of spermatophores:
What insect is this in?
Where do the males attach the spermatophore?
Field crickets.
Males attach the spermatophore to the entrance of the female reproductive tract.
Continuation from selective use of spermatophores:
What might females do?
Who are females more likely to do this for?
What are they doing here?
Females might remove and consume the spermatophore before the sperm transfer is complete (before it enters and fertilises the eggs).
Smaller males.
They are exerting choice for large males (for them they would leave the spermatophore and the sperm enters the female and those males get to fertilise their eggs).
Selective termination of copulation:
What might females do?
What is it hard to know?
Give an example of a situation which is unambiguous.
Terminate copulations in a selective manner.
It is hard to know if the copulation was ended by the male or female.
Female spider eats the male.
Continuation from selective termination of copulation:
Name a spider.
What do these spiders do?
In this species, what is the difference between the male and the female?
Is this counterintuitive?
Orb-web spider.
Females terminate copulation by attacking the male (they often eat him).
The male is much smaller than the female and being small is good and desirable,
Yes.
Continuation from selective termination of copulation:
What else happens?
What is this? Explain.
When a female mates with two males and they eat the second male, if the second male was smaller they wait and do not eat him so soon allowing for greater sperm transfer, he copulates for longer (he can fertilise more of her eggs).
Counterintuitive- they do not eat the small male quickly so he can fertilise all his sperm but they will eat the big males quickly.
Sperm ejection:
Name an animal.
What type of copulation do they have?
Who do females prefer to copulate with?
Feral fowl (wild equivalent of chickens).
Coerced copulation- The males run around trying to copulate with females.
Dominant males (they do not mind it).
Continuation from sperm ejection:
What happens if they are sexually coerced by subordinate males?
What else can they do?
The females will try to manipulate the behaviour of dominant males to reduce the likelihood of insemination (getting the dominant males to then inseminate them).
They can eject the sperm (dump it out).
