lecture 16 Flashcards
Sexual dimorphism
differences in phenotype between males and females of the same species as result of differences in genetic material; ex. in humans, males are on average taller than females
sexual selection
selection for phenotypes that may reduce survival, but that increase mating success; ex. Peacock’s elaborate tail, which greatly impairs mobility
intra-sexual selection
mating success determined by within sex interaction; ex. male-male combat
inter-sexual selection (epigamic selection)
mating success determined by between sex interactions; ex. female choice of males
Fecundity selection
selection on female fecundity (number of offspring produced); different than mating success (number of mates); larger females can produce more eggs which increases reproductive fitness
Sexual vs. natural selection in marine iguanas
large males are more successful at attracting mates and so sexual selection favors large males; but there is a cost of large size in El Nino years where food is scarce and unable to meet energy demands
anisogamy
form of sexual reproduction involving the union or fusion of two dissimilar gametes (rather than two isogametes); ex. large immobile egg and small mobile sperm
Bateman’s principle and experiments
greater variance in reproductive success among males than females; males have greater success as number of mates increases, but females are just as successful with one mate (success not increased with multiple mates); males are limited by number of females and females are limited by resources and good genes
rough skinned newts
when males had increased number of mates, produced much more offspring; females barely increased number of offspring when more matings
male combat in red deer
reproductive success is more variable in males than females; some males don’t produce any offspring while some have over 20 offspring
broad nosed pipefish
females compete for access to males and access to their pouches; males are investing the most and so they have less variance in mating success than females; an example of role-reversed species
Conditional mating strategies
alternative phenotypes expressed by low ranking individuals to try to make the most of a bad situation against the more dominant ones; doesn’t generally have the same fitness between tactics
Dominance behavior in elephant seals
males who are more dominant are getting more mating opportunities
Dominance behavior (monkeys?)
alpha males are getting more mating opportunities and mate in the open; subordinates get less and mate in a hidden place
Enthusiasm and the Coolidge effect
used to keep chickens on whitehouse lawn and there was only one rooster who mated with all of the females; rooster will have enthusiasm each time because presented with different female; when presented with a new mating partner, more likely to take part in a mating activity and less time in between mating activities
Mate guarding in frogs
males jump on females’ backs and females have to carry male for extended period of time to prevent her from mating with anyone else and ensure that his sperm is fertilizing her eggs
sperm competition
sperm from some males have greater chance of fertilizing eggs than others, may be due to different amounts of sperm ejaculated or displacement or inactivation of rivals’ sperm
sperm competition in fruit flies
male fruit flies were reared alone or with another male, and then were allowed to mate with female; males in presence of other males produced 2.5 times more sperm than males reared alone
Black winged damselflies and sperm competition
scoop out previous male’s sperm before mating
Ghost spider crab- sperm competition
release a secretion that cements around another male’s sperm, preventing it from fertilizing egg
cabbage white butterfly
after mating, males leave behind chemical repellents that stink and other males find repulsive so other males wont want to mate with female
red-sided garter snakes
after males mate, they create a plug that renders the female unattractive to other males; male bees use a similar process to make female bees unattractive
