Lecture 11 – Congruence and Conflict in Sexual Interactions
1. Good genes (A Happy Story)
i. Indicator models and condition dependence
ii. Good genes – the covariance of condition and the preference
b. Sexual conflict (A not so happy story)
i. The sexes in conflict
ii. The evolution of sexually antagonistic traits
iii. Genetic manipulations of those traits
2. “Indicator” models and condition dependent trait expression
a. The essence of these models is that preferred traits reflect the genetic quality of the
male. Females maybe choosing traits which are indicators of the genetic quality of the
male. The genetic quality of the male is reflected in the trait which is called conditioned
dependent. If the male is healthy he will produce large ornaments.
b. Fisher and Williams(contribution to aging) reasoned that females would be favoured to
select healthy males as fathers, and that only healthy males could afford to
c. Zahavi introduced the idea of a handicap.
3. Are sexually selected traits condition dependent? is it dependent on the male expressing them?
a. Much correlational support exists: if you go out and measure the expression of trait and
health, it is correlated
b. Considerable experimental evidence exists – raise males in different nutritional
conditions. And if they are raised in good nutritional conditions you expect them to have
these good dimorphism traits, if the nutr. Conditions are not good, then you cant seen
developed traits. Their phenotype is low quality.
c. Variance in condition is usually generated with an environmental manipulation – eg
d. If sexually selected traits are more condition dependent than other traits, than both the
degree (and quality) of sexual dimorphism itself will be condition-dependent –(condition
of the population)differences between the two sexes: sexual dimorphism.
i. If you go to one population where the condistions are good like high food, you
see that the two sexes are very differtn, if the conditions are poor, the the tewo
sexes are not that much different . this is so ecause in high food conditions you
crave males who are healthy and express good trait.s
4. Sexually selected traits have heightened condition- dependence
5. Sexually selected traits have heightened condition- dependence
6. Is the transcriptome condition- dependent?
a. Whole adulttissue
b. 14KD.melanogaster genes.
7. 100s of new genes are recruited into the dimorphic state
8. Sex-biased genes become more sex-biased 9. Are the gonads driving the majority of the condition dependence seen in sex-biased genes?
10. Can female preference remove “bad genes”?
11. Good genes: sexual selection removes“bad genes”
a. Females identify “stud” and “dud” males
b. Studs and duds father offspring
c. Non-mating fitness of offspring assayed
d. Repeated in 3 independently derived populations
e. Sexy males produce healthy offspring
12. Are sexual and natural selection are congruent in adapting populations
a. Populations that move into a new environment will adapt by natural selection Pat Lorch
b. If females discriminate against maladapted males (bad genes), then
c. sexual and natural selection will be aligned:
i. Sexual selection will accelerate adaptation
d. Populations with sexual selection will evolve to higher fitness than those without
13. Sexual and natural selection are congruent in adapting weevil populations
a. Populations evolve on “old” or novel host, under monogamy (no sexual selection) or
polygamy (sexual selection).
b. Rapid development is favoured in novel host.
c. After 35 generations of adaptation:
i. beetles adapt to novel host (fitness up)
ii. adaptation is accelerated with SS
14. Sexual Conflict
15. Just how harmonious are male/female interactions?
16. Costs of mating
a. Most females mate multiply and it is superfluous wrt gaining sperm
b. Costs include:
c. • time, and energy
d. • STI’s
e. • increased risk of predation
f. • injury
g. • death
17. Costs of ejaculate transfer
a. Ejaculates are often only a few percent sperm, the rest is a cocktail of
b. proteins and peptides (100+ in flies)
c. These molecules can be detected in the bloodstream (even in humans!)
d. shortly after mating.
e. They have large effects on gene regulation, reproduction, behaviour etc.
f. Potential costs include:
i. changes in reproductive allocation
ii. reduced remating
iii. reduced lifetime fecundity (sex peptide)
18. Divergent interests and sexually antagonistic selection a. Parental Investment Theory (R.L. Trivers)
b. • Sexes differ in their reproductive investment
c. • Members of the sex that invest little in
d. offspring will compete among themselves to
e. mate with members of the sex that invest more
f. in offspring
g. • Male (female) competition and female (male)
h. choice Geoff Parker
i. Sexual conflict
j. 1. The evolutionary interests of the sexes differ
k. 2. Therefore selection acting on the two sexes in an interaction (or on a
l. single shared trait) will often be antagonistic
19. How wide spread is sexual conflict I?
a. Consider virtually all interactions between the sexes. In the absence of life-long
b. genetic monogamy, all will be subject to conflict.
c. Mating rate and duration
d. Mate choice
e. Sperm use
f. Egg laying rate
g. Parental investment
h. There will be battles over these interactions,
i. with the potential for evolutionary arms races
20. Antagonistic Adaptations in Rheumatobates
a. Water striders: rheumatobates:
b. If you look at a standard water stirder, that is how the female looks like in the
rheumatobates. The standard water striders antenaae looks like the dstandard water
striders antanne. But in this species male antannes have spikes and clasps. And it looks
like a grapsing apparatus. It is made to holding onto the female when she resists the
enatannes is taken ovr from one force of sexual selection
21. Sexual Conflict: sexually antagonistic selection on a “shared trait”. Often resulting from sexual
a. W = fitness
b. According to batesm : males mating rates goes up fitness goes up
c. Females intermediate mating rate if they mate too high they will suffer a cost, but
non of the benefits , like STD. because they don’t need all that sperm, they need
some sperm, because they need it.
d. Mating rate is relaly ow, it is going to increase, because it is good for both. But when it
goes high then it is not good for females, good for males. So CONFLICT! Ove rthe mating
rate of the two sexes. This is what happens in waterstriders.
e. Mating a lot for females is not good. : males might be trying to mate females 2 – 3
minutes. They will mate 10- 15 times a day. Females st