BIO220H1 Lecture Notes - Lecture 11: Gerridae, Sexual Conflict, Sexual Selection
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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
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. Much correlational support exists: if you go out and measure the expression of trait and health, it is correlated. 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. Variance in condition is usually generated with an environmental manipulation eg nutrition. The evolutionary interests of the sexes differ: 2. Therefore selection acting on the two sexes in an interaction (or on a single shared trait) will often be antagonistic: how wide spread is sexual conflict i, consider virtually all interactions between the sexes.