Week 7 - Mate Choice and Reproduction

Question 1

Choosing a mate: what are the main conflicts between sexes?

Answer 1

1. Anisogamy - conflict between the size of the female and male gametes
   - The sexes invest differently in reproduction (males QUANTITY, females QUALITY)
2. How many partners to have
3. Why bother choosing a mate

these sexual conflicts can explain why elaborate behaviours evolve and why populations may become reproductively isolated

Question 2

What can sexual conflict drive?

Answer 2

An ARMS race - males are under selection to reproduce with as many times - their reproductive success is limted by availability to females

Eg. Trinidadian Guppies - maximise success by mating with new females

Female reproductive success is driven by availability of materials

Question 3

How many partners: What is MONOGAMY?

Answer 3

Monogamy - Each sex has one partner

Monogamy is favoured when:
1. Input from both parents is needed to raise offspring
2. Male has to guard mate to ensure he is father of offspring
3. Low chance of meeting many females

Question 4

How many partners: What is POLYGYNY? What does it promote? When is it favoured?

Answer 4

Male has MORE THAN ONE PARTNER, female has ONE PARTNER

Example: Red Deer
- Males can mate with all of the group

Polygyny promotes:
1. Conflict between males: males competing with each other, defending resources, defending females, can lead to weaponry

2. Choosiness by females
   - male features are picked for/against

Polygyny is favoured when:
- One sex is rare
- Males can control resources
- Females can exert choice

Question 5

How many partners: What is POLYANDRY?

Answer 5

Females have MORE THAN ONE PARTNER, males have ONE PARTNER

Example: Spotted Sandipiper
- Females behave like males (fight for territory etc.)

Favoured when:
1. Females can escape parental duties
2. Females require resources provided for by >1 male
3. Males biased sex ratio (lots of males)

Question 6

How many partners: What is POLYGYANDRY?

Answer 6

BOTH HAVE MORE THAN ONE PARTNER
1. Males gains several females
2. Males unable to exclusively defend female
3. Females gain access to wide range of resources
4. Females confuse males over paternity = increased paternal care, decreased infanticide
5. Females access to many males

Favoured when males can’t monopolise females AND females gain from multiple matings

Question 7

Sexual Selection: What is the difference between intersexual and intrasexual selection?

Answer 7

1. INTER - one biological sex chooses mates of the other sex to mate with
   - selection between the sexes
2. INTRA - compete with members of the same sex to access members of the opposite sex

Sexual selection occurs because of conflict over reproductive investment

Question 8

What are the direct benefits for females choosing their mate?

Answer 8

Territory
Gifts (food)
Paternal care - females can invest in their own health
Reduced harassment

Offspring live longer and produce more offspring themselves
Genetic benefits

Females should:
- Prefer males with exaggerated signals that cannot be faked
- Maximise their benefits
- Pay attention to signals of benefits