Mate Choice Flashcards
mate choice is also called
intersexual selection
which sex typically is choosier, and why?
females
they have more to lose in reproduction (they invest more) so female choice is more of a selective force
what do females choose for?
direct benefits (nuptial gifts, paternal care, good territories, good resources.)
indirect benefits (genetic quality)
what do females gain when they choose for male resources?
males use food to convince females to mate.
Nuptial gifts
females prefer bigger nuptial gifts, and will mate longer the larger the nuptial gift is
what do females gain when they choose for resources held by males?
a good territory with minimal predation or plenty of food
what do females gain when they choose for parental ability?
males who can take care of young.
may dump eggs for male to care for, must be able to defend nest
may need help getting food for chicks. If father brings more food, more young can develop.
what do female sand gobies look for when choosing a male?
they prefer to lay eggs in a nest that already has eggs in it.
widow birds study
male tails are incredibly long.
do females prefer long tails?
3 groups: shortened, normal, elongated tails
females preferred the elongated tails, meaning its a sexually selected trait despite its drawbacks (harder to fly, costly to produce/maintain, increased predation risk)
what do females select for in song sparrows?
larger song repertoires
what is unique about blue satin bowerbird’s courtship?
they make nests with “runways” in the middle, and collect as many blue things as they can for decoration.
what do females gain when choosing for indirect benefits?
better genes for their offspring
cryptic female choice (and ex.)
post-copulatory control of fertilization by females
(ex. differential ejection of sperm)
pecking order in chickens
dominance is heritable, so females gain from mating with dominant males. will eject sperm of lower ranking males when mating with more dominant male.
dominant male will sometimes force copulation
direct benefits
parenting, food, resources, good territory.
indirect benefits
elaborate displays convey male quality, which can be inherited by offspring. Genetic quality often means disease resistance, genetic complementarity, and symmetry.
Fisherian runaway selection model
trait has selective advantage, and will be selected to its extreme over and over, until the trait is too costly to produce/maintain, and females stop preferring it.
Females choose the ornamented males to ensure their sons will have the same reproductive success.
The genes for preferring the trait and having the trait are often bundled, since the mother prefers the trait and the father has it. Size of trait is correlated with degree of preference.
good genes/handicap model
males with elaborate traits convey quality- if they are able to survive with these inconvenient traits, they must be a superior male.
The trait could also indicate good genes:
- genetic complementarity (high heterozygousity in offspring, should female mate with him)
- disease resistance
-foraging skills
- symmetry (if male was able to develop symmetrically, it means he was able to maintain normal development under stress)
MHC
immune cell surface proteins. Recognizes foreign molecules in invertebrates, bind peptide fragments from pathogens and display them for T cells.
Females tend to choose males with diverse MHC genes.
fluctuating asymmetry
bilateral symmetry is an indicator that the male developed normally in the face of stress.
chase away selection
preference for trait evolved prior to sexually selected trait, which was evolved by males to exploit pre existing sensory biases of females. Female fitness declines in mating with these males, as this trait is not an indicator of quality, it is simply exploiting a sensory bias she already had for some other reason.
creates a loop where because her fitness declines, the female’s mating threshold increases for the trait.
peacock study
males with more eyespots mated more often (eyespots where cut out)
males with longest tails also had a higher immune response when injected with PHA
song sparrow study
males with larger repertoire sizes have greater immune response when injected with PHA.
fluctuating asymmetry study
male fish had bars removed via dry ice, females didnt prefer them, when they were made symmetrical, females preferred them.
guppies study
sensory bias in female guppies was tested using different coloured dishes, females preferred and pecked the orange dish much more than other colours.
