Biology 106 sexual selection notes

• heritable differences expressed in phenotype
• type of natural selection (differential fitness and thus differential allele frequencies)
• mating is not random (more or better mates)
• traits involved change reproductive opportunities (fertilization and male acquisition)

• between one sex and the other (other sex makes choice- usually females)
• impressed or not?
• Ex: blue footed booby, sage grouse, peacock
• Lek- males gather in common area to win female attention

• competition and selection among individuals in the same sex
• Ex: dominance- gets you access to mates, territory (seal, ram)
• access- able to get mates (post mating competition- crabs)
• territories- not all fighting (bird songs indicate territory)

• what happens to sperm after mating
• Ex: when females mate with 1> male (pollen)

• more/better matings +choice= sexual selection
• not mating+acts on both sexes+ side effects of natural selective pressures= natural selection
• certain naturally selected traits can be useful for sexual selection

• reproductive success variable
• dominant males control access and resources
• pay-offs are variable

• females and males look different
• can be both natural and sexual selection
• Ex: hair, insect genitalia, wasp (ovipositor)

• shows fitness of the male to females
• costly signals are HONEST- females pick for real fit males, not unfit males that fake it
• Ex: small deer with huge antlers doesn't signal health because the signal is too costly
• Ex: carotenoids (bright orange beak)
• - concept: I've got a surplus of carotenoids so I can afford to waste them

• symbols in place of actual weapons
• Ex: arms race, weapons display rather than waste energy, risk injury

woodpeckers can amplify sounds with gutters, can fake the signal

• signal is so costly, continued survival is highlighted
• Ex: giant antlers, size, armoring

• arbitrary signal that imitates food, other important factors
• opposite sex who can see it faster will mate with them

selection caused once reasonable signal to get too big

not always in line because constly signals both hurt species fitness and increase reproductive opportunities

• being too attractive will hurt survival after a certain point
• Ex: bull frog and croak being eaten by bats

• big horns allow control over harem, mates
• copulatory organ is smaller, however

• ecological impact
• fungi take over minds of moths, flies, and ants
• there is a limited repertoire of chemical receptors and some coincidental matches!