Mate Choice Flashcards
Mate Choice for Direct Benefits
a) choice for male resources (nuptial gifts)
b) choice for resources held by males (territory)
c) choice for parental ability (ie. hen harriers choose males with the best feeding rates, mottled sculpin females chose males with eggs already in nest)
d) choice for resources and parental ability
Mate choice in the absence of direct benefits
Choice for genetic quality (as it influences offspring quality).
Preference for elaborate displays
Plumage (Peacocks)
Song (Song Sparrows)
Courtship (Blue Satin Bower Birds)
Differential Ejection of Sperm in Chickens
Dominance is heritable, and females gain from mating with more dominant males. But they lack control over who they mate with; copulation is often forced on them. The only control they have is in sperm ejection.
Females are less likely to eject the sperm of dominant, high ranking males.
Fisherian Runaway Selection Model
Positive feedback causes a runaway mechanism. Having the trait is an advantage, which causes the trait to be selected further.
- Female preferences initially have selectively neutral / slight positive effects on fitness.
- Females tend to mate more with those males.
- The offspring has both the genes for that trait and the preference for that trait.
- Genes and preference become bundled.
- Effect snowballs.
Assumes no adaptive value other than preference.
Good Genes / Handicap
Male traits provide females with information about male quality, indicators of good genes.
Could indicate…
- good genetic complement to females (genetic dissimilarity is preferred)
- disease resistance (more ornamentation = more healthy, resilient)
- foraging skills
- conditions during development (symmetrical males had normal development course under stress)
ex. Repertoire size in song sparrow = greater phenotypic immunity.
ex. Seychelles warblers choose mates with diversity in MHC (good genes AND genetic complementary)
Fisherian + Good Genes vs. Chase-away
Fisherian + Good genes posit the traits and preferences evolved together.
Chase-away posits that the preference involved before the trait.
Chase-away Selection
Sensory bias already exists (ie. for foods rich in colour = rich in nutrients), then a mutation happens that gives a male that trait (orange in guppies). They’re mated with more, and the trait spreads.
