lecture 18 Flashcards
MHC study of genetic similarity in mice and humans
In mice: females spent more time with males of dissimilar MHC than mice with similar MHC, this result was reversed in lactating females
In humans: females perceived male’s scent as more pleasant if dissimilar MHC, but result was reversed if on contraceptives
Sensory bias
females have latent preferences that male signals exploit; female preference for a trait evolves before the actual evolution of the male trait
sensory bias in trinidad guppies
female guppies are attracted to orange, sexual selection then favors males with lots of orange- works on a preference that was already established in females
Sensory bias in swordtail fish
to determine how a preference exists before a trait, can manipulate a closely related species in the phylogeny that hasn’t yet developed trait to see if the preference exists; when they added a sword tail to Xiphoporus (doesnt normally have swords) found that females do have a preference for the males with swords
Mate Choice Copying: Guppy experiment
young females behind glass could observe another female choosing between two males and then were released to make their own choice; female guppies normally would choose bright orange males; however, females copied model female’s choice even if he was the less orange, lower quality male; shows cultural transmission of mating preferences- likely to teach what to look for in a mate and reduce the cost of assessment
Sexual selection post-copulation
choice does not end with copulation; male sperm competition involved conflict between sperm of varying quality; female sperm preference- egg itself exhibits some level of choosiness for certain sperm
polygyny
prolonged association and exclusive mating relationship between one male and two or more females at a time
polyandry
prolonged association and exclusive mating relationship between one female and two or more males at a time
promiscuity
no prolonged association between the sexes and multiple matings by members of at least one sex
socially monogamous
long term association between a male and female, which serves the need for parental care; does not necessarily imply genetic monogamy- in which only mate with one another; in alpine marmots, while most offspring belong to “father” figure, sometimes some of the offspring are a result of the female mating with other males
when does monogamy exist in species?
when males are unable to monopolize more than one female, when there is a necessity for bi-parental care, in order to mate guard
Termites and monogamy
females are scarce or widely distributed and you have massive mating flights after a rain; there is the inability to monopolize more than one female and so males mate with one female and then start their own colony
Hornbill and monogamy
example of the need for bi-parental care; female is cemented into tree with offspring because predation is so high, and the male is then needed to forage for food, or else the female and offspring will die
Mate assistance hypothesis of monogamy
paternal care is needed to ensure offspring survival; this then results in the synchronization of male and female reproductive cycle; example: seahorse males carry eggs in pouch
Mate guarding hypothesis and Kirk’s dik-dik antelope
males mate guard by pooping on top of female’s poop so other males wouldn’t be attracted to her; assumes that unguarded females would seek other mates; males are expected to mate guard if there are more males than females or if mating is synchronous
Mate guarding in burying beetles
female-enforced mate guarding; females attack if males show interest in other females; females push males off perches so they can’t secrete sex pheromones
Polygyny Threshold Model: Orians
a male’s territory quality is correlated with mating success; polygyny is more common in environments with more variation in territory quality, where being a secondary female on a high quality territory may have higher fitness than being a primary female on a low quality territory; in red-winged blackbirds, females chose paired males with high quality territory over unpaired male in low quality territory, resulted in doubled offspring production for the male
Sexy Son Hypothesis
when male provides no material benefits, choosing an attractive polygnous male is best way to produce reproductively successful sons; attractiveness is associated with good health, you want to ensure that you will produce offspring that will be able to successfully produce their own offspring
Best tactic hypothesis and Yellow Bellied Marmots
making the best of a bad situation; increased harem size (male defends group of females) is associated with lower fitness in females; however, females do not leave because very abusive to individuals that try to leave the group; fitness cost of leaving is too great, so females stay even though the large group reduces her reproductive fitness
resource defense polygyny
male scorpionfly dangle prey item during mating; with a large enough item, males are able to have longer copulation time and may even be able to use the same prey item to mate with additional females
Scramble competition polygyny
expected when females or resources are widely distributed or receptive for short period
Lek polygyny
hotspot for mating where males and females come together and females do their “comparison shopping” to pick a mate; females usually only mate with one male, so most males don’t get to mate at all; even though selection pressure should be huge for the attractive traits, variability still exists
Polyandry
one female mates with multiple males; thought to occur when male-biased sex ratio, or high predation rate, or limited clutch size (amount of offspring); reproductive success of females is increased with the number of matings
Promiscuity
multiple mating partners for both sexes; usually low parental investment by males and often by females also; ex. Anchovy fish- females lay thousands of eggs at once and most won’t survive
