6. Sexual Selection
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Sexual selection vs. Natural selection
- traits favored by sex - not necessarily survival
- ex. bright colors.
Intersexual vs intrasexual selection
- inter - between male and female -showing off to mate. Opposite sex chooses the traits that continuer on.
- intra - between male and male OR female and female - showing off to competition. Same sex chooses the traits that continue on.
- differences in males and females that only exist for sexual gain
- ex. horns in males are only used to fight other males.
the sex with the greater variance in reproductive success is the sex who mates more often and will compete for mates. Therefore, sexual selection acts on this sex more often. Favors traits for competitive aka intrasexual selection.
operational sex ratio
fertilizable females/sexually active males
a low threshold for males sexual arousal especially with the introduction of more than one female. Males opportunity to mate with many females have higher sex drive than with one female
variables that influence OSR
*age of sexual maturity, *parental investment, migration, food supply.
Clutton-Broch & Vincent
- its not about "parental investment" thats too hard to measure
- its about reproduction rates
Fischer run away sexual selection
- sexy sons
- the preference is spread in a species and reinforces a trait into where it is almost economically costly but it is sexy
costs of choosiness 1234
- predators exposure
- opportunity cost - what else could you be doing? gathering food?
benefits of choosiness
non genetic resources
polygyny threshold model
if females will get better resources by mating with a pre-mated male, she will do so instead of getting a new male
how is variability possible when females prefer similar things?
answers to leks paradox
- 1. mutation
- 2. fluctuating selection
parasites are fluctuating selection. Resistance to parasites will always be heritable
traits that are important to fitness are + or - heritable?
males that have been through worse environments and survived are more attractive
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