Week Seven Flashcards
How do water strutters display co-evolution of sexes?
Females evolve to produce pincers, which protect against the male.
-Males then evolve hooks to latch onto female.
How did Bill Rice study co-evolution of sexes?
He stopped the evolutionary potential of the female, but not male fruit flies.
- Other one wins –> Male fitness increased when females were removed from the gene pool.
- Males adapted to the “non-responding target”.
How do male sfps interfere with the interests of females?
They stimulate egg production. Decrease sexual receptivity. -Decrease female attractiveness. -Help transport and store sperm. -Form mating plug. -Reduce female longevity.
When would intralocus sexual conflict occur?
If optimal trait values differ between the sexes and there is a common genetic basis then there is potential for conflict at a given locus.
When reproductive interests do not agree.
Why would intralocus sexual conflict occur?
Sexes acquire fitness in different ways.
- New alleles are usually expressed in both sexes
- Fitness effects of these alleles may be sex-specific, even opposed.
How do males and females evolve in response to ISC?
Genetic mechanism?
Mechanisms to promote independent control of gene expression in females and males are expected to evolve in response to intralocus SC.
Hormonal regulators SEx-specific modifiers Gene-duplications -Relocation of loci to sex chromosomes -Genomic imprinting
What are clone-generators?
Female clone generators are XXY, they pass the Y-chromosome to sons. Males pass their X-chromosome (and all others) to offspring.
- CG constructs make all main chromosomes into a single linkage group
- Dipteran Males lack molecular recombination
What did they measure and what were the results of Prasad’s male-limited evolution?
They measured relative fitness between control male and females; and male-limited males + females.
- -> Male-specific fitness improved, at the expense of female fitness.
- Female fitness was more variable, best genes in male went to 0.1 fitness for females.
What was the phenotype of males in male-limited genomes?
Higher fitness Male-like growth pattern. Higher 'courtship efficiency' No change in feeding behavior -Increased immunocompetence.
What was the phenotype of females in male-limited genomes?
Lower fitness
- Male-like growth pattern
- Attract less courtship
- Spend less time feeding
- Increased immunocompetence.
What happened to female wings when they underwent male-limited selection?
The wings became more symmetrical, smaller, lower mass/size ratio.
-Increased developmental stability of males but decreased the developmental stability of females.
What is the dimorphism of CHCs between sexes?
Females have more long chain HC’s, males have shorter HC’s.
-Although many are expressed in both.
What did Foley et al. find when they looked CHC’s after 82 generations of male - limited evolution?
No response to 82 generations.
- Of the 34 assayed, only one differed significantly between control and ML-evolved populations.
- CHCs appear to be under completely independent control in the two sexes.
- They evolution of a separate set of genes for the same compound in each sex may suggest a history of sexual conflict, now resolved.
- No evidence for adaptation to clone-generator females used in selection protocol.
- No evidence of the ‘arms race’ dynamic Rice described.
What situations cause characteristics to change during male-limited selection?
Only characters under shared genetic control changed under ML selection.
-Traits already linked to expression in males (sperm, CHCs) did not evolve.
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What happens when male flowers are selected to be more like female flowers?
Females have few, larger flowers. Males have many, smaller flowers.
- They would be selected to make larger flowers, however this would not increase the # of flowers for pollen and anthers!
- Female-like male would have successful daughters, but no successful sons.
What does exposure to estrogen in the womb correlate with in Rams?
8% gay rams? Something like that?
What did Stulp et al. examine in the Wisconsin Longterm Study?
Over 10000 people who graduated from Wisconsin high schools were tracked for over 50 years.
- Looked at brother-sister pairs.
- Shorter women had more kids than taller women.
- Average-height men had the most offspring.
What is the evidence for maternally inherited factors favouring male homosexuality and promoting female fecundity?
Female relatives of gay men have higher fertility than female relatives of straight men.
- Fitness costs of homosexuality recovered through opposite-sex relatives
- Effect matrilinear, implying X-chromosome linkage.
What are the effects of interlocus sexual conflict?
(arms race) Expected to propel population divergence and speciation.
What are the effects of intralocus sexual conflict?
(tug of war) Provides a reservoir of variation for fitness itself.
Why are there organisms with traits that clearly compromise survival?
Sexual selection!!!!
–> Evolution of extravagant traits that are costly and clearly not evolved in aid of survival.
What is darwin’s model of SS?
Males + females are variable with respect to phenotypic quality.
- -> Males move to breeding grounds before females
- -> Highest-quality females are ready to mate sooner, so they pair with highest-quality males
- Lower-quality females pair with lower-quality males.
- Highest quality matches will produce more offspring than lower quality pairs.
Why does the classic story of the long giraffe head not hold up?
giraffes don’t often forage high on trees,especially in the dry season.
- Neck makes grazing and drinking difficult.
- Costs in terms of speed, agility and (presumably) reproduction.
What did Simmons & Scheepers suggest about the giraffe neck?
That it might be part of a sexually selected weapon system.
- Male head armoured and 3.5x heavier than female’s.
- Fierce sparring and combat among males.
- Female choice correlated with size.
- Therefore……SS is important n maintaining the neck of the male giraffe.
