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.
