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.
sexual dimorphism
differences in males and females that only exist for sexual gain
ex. horns in males are only used to fight other males.
Bateman principle
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.
OSR
operational sex ratio
fertilizable females/sexually active males
Coolidge effect
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
time
energy
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
Lek's paradox
how is variability possible when females prefer similar things?
answers to leks paradox
1. mutation
2. fluctuating selection
Hamilton-Zuk's hypothesis
parasites are fluctuating selection. Resistance to parasites will always be heritable
traits that are important to fitness are + or - heritable?
less heritable
handicap models
males that have been through worse environments and survived are more attractive