Evolution of sex ...

Question 1

What is sperm competition?

Answer 1

The competition between the sperm of two or more males inside the female’s reproductive tract

Question 2

Example of outcompeting rivals: Damselflies

Answer 2

• Males have specialised penis whuch removes other males sperm before they mate

Question 3

Sperm competition example: insect mating strategies

Answer 3

Polyandrous males produce a higher proportion of viable sperm than monogomous males

Question 4

How do males in monogomous species protect againts extra-pair copulations?

Answer 4

Mate guarding to drive off other males.

Question 5

How effective is mate guarding in sychelles warblers?

Answer 5

• Males drive down extra pair copulation by mate guarding.
• Study placed fake egg in nest to ‘switched off’ mate guarding
• Many extra-pair copulations occurred.

Question 6

Blue milkweed beetle: Experiment background

Answer 6

Males stay mounted on females for some time after copulation
Form of mate guarding

Question 7

Blue milkweed beetles: experiment

Answer 7

• Experimentally removed males straight after copulation
• 25% of males found new mate within 30mins
• 50% of females found new mate within 30mins

Question 8

Blue milkweed beetles: what do the results show?

Answer 8

• Mate guarding is beneficial when males father above 40% of offspring

Question 9

Not all mates can be with their partner all the time: How do they ensure paternity?

Answer 9

• Male Fulmars copulate over 50 times with partners to outcompete any other males
• Frequent copulation ensures optimal timing of insemination relative to fertilisation
• Sperm competition

Question 10

What is cryptic female choice?

Answer 10

Female manipulation of sperm inside her reproductive tract so that a preferred male fertilises her eggs

Question 11

How do chickens use cryptic female choice to ensure forceful mating from a subordinate male doesn’t fertilise her eggs?

Answer 11

Can eject sperm from their cloaca after mating

Question 12

Why do female dunnocks eject sperm?

Answer 12

• A male may peck at his partner’s cloaca if another male has been near her. In response she may eject a droplet of fluid containing sperm, but this sperm is non-viable.
• First thought females were ejecting other males sperm, but she is just ejecting dud sperm and making way for new males sperm

Question 12

How does a larger nuptial gift benefit males hanging flys?

Answer 12

• Longer sperm transfer whilst female eats gift
• Smaller gifts resulted in short incomplete sperm transfer

Question 12

Alternative mating strategies in scorpian flies

Answer 12

• Large, Medium and Small body sizes
• When large males are removed from a population the medium males takes up large males mating strategy

Question 13

Alternative Male Morphs in an Isopod

Answer 13

• Each male mating strategy has equal mating success
• Genetically predisposed?