2: Sexual conflict

Question 1

Define Intra-locus sexual conflict

Answer 1

Trait on same gene (on same locus)
Tug of war over a trait with shared genetic basis

Question 2

Define Inter-locus sexual conflict

Answer 2

Trait in one sex, interacts with a trait on a different locus on the other sex

Question 3

How does intra-locus sexual conflict arise?

Answer 3

→ Arises when a trait has a shared genetic basis and contradictory selective pressures act on the sexes
E.g Body size in Drosophila

Question 4

How does intra-locus conflict effect diversity?

Answer 4

→ Intra-locus conflict leads to balancing selection and elevated genetic diversity

Question 5

How does inter-locus sexual conflict arise?

Answer 5

Conflict arises because natural selection may favour different traits in different sexes, so the genes of these traits are in conflict

E.g Traumatic insemination in Bean weevils
- Optimal for males to be promiscuous and for females to be choosy
- Males evolve traits to improve repro competitiveness (spiky peen) while females evolve traits to reduce direct costs (try to kick off males attempting to mate)

Question 6

Fill in the blanks

Due to sex linkage:
_______ alleles on X should be ____ often selected for female-specific effects

_________ alleles on X should be ______ often selected for male-specific effects

Answer 6

Due to sex linkage:
Dominant alleles on X should be more often selected for female-specific effects

Recessive alleles on X should be more often selected for male-specific effects

Question 7

What are some evolutionary outcomes of inter-locus sexual conflict?

Answer 7

Many different outcomes:
1. Resolution & coevolution
2. Arms race (escalating changes in repro traits)
3. Dimorphism (sexes are distinct, means they can optimise their own repro strategy)
4. Balancing selection (balanced polymorphism = multiple allales are maintained in pop. so no one trait dominates)