Chapter 10: The Evolution of Mating Systems

Question 1

polygyny

Answer 1

more than 1 female, but only one male

Question 2

polyandry

Answer 2

more than 1 male, but only one female.

Question 3

polygynandry/promiscuity

Answer 3

more than 1 female and more than one male.

Question 4

monogamy tends to ____ male reproductive success and ___ female reproductive success.

Answer 4

monogamy tends to COUNTER male reproductive success and ENHANCE female reproductive success.

Question 5

T/F pairing of one male and one female always equate to genetic monogamy

Answer 5

false. social pairing/monogamy does not always equate to genetic monogamy. in 90% of bird species, one or both members of a socially monogamous pair engages in extra-pair fertilizations.

individuals who are socially monogamous tend to actually not be genetically monogamous.

Question 6

costs of multiple mating in males

Answer 6

1) time and energy spent searching for extra mates
2) risk of predation during search
3) risk of acquiring an STI

costs of multiple mating may exceed benefits, resulting in monogamy.

Question 7

the higher degree of polyandry in a species, the ____ WBC’s

Answer 7

the greater the amount of white blood cells. this is a measure of immune system competance and polyandry. in polyandorus species, the immune system is upregulated to counteract potential STIs

Question 8

4 hypotheses to explain monogamous mating systems

Answer 8

1) mate limitation hypothesis
2) mate guarding hypothesis
3) mate assistance hypothesis
4) infanticide hypothesis

Question 9

explain the mate limitation hypothesis and provide examples

Answer 9

monogamy is likely to evolve when potential mates DO NOT FORM GROUPS and roam widely, making them costly to locate.

ex/ rock haunting possums. their burrows are so far away from each other that the males couldn’t possibly try and protect multiple home ranges.

Question 10

explain the mate guarding hypothesis and provide an example.

Answer 10

monogamy is likely to evolve when individuals have the ability to restrict mating behavior in their partner.

ex/ burying beetles (but the female is the guardian)

Matte guarding monogamy is also seen in rock possums. Mate guarding is facilitated by the small discrete home ranges occupied by females.

Question 11

explain the mate assistance hypothesis

Answer 11

monogamy is likely to evolve when resources are so critical to successful reprodiction that both parents are necessary to rear young. ex/ djungarian hamster.

if there is increased offspring survival when you have 2 parents providing resources, species are more likely to be monogamous.

Question 12

explain the infanticide hypothesis

Answer 12

monogamy is likely to evolve when the risk of infanticide is high and a partner can provide protection against infanticidal males.

Question 13

explain mate guarding in crickets

Answer 13

a male that has acquired a mate remains wiht her in his terrirtory. if the pais is attacked, the male permits the female to rush into the burrow first.

Question 14

explain the female-enforced monogamy of burying beetles

Answer 14

females are the ones that mate guard. when a male has a buried carcass, he will release pheromones to attract more females. when the first female smells the pheromone, he hurries over to push hum off his perch, and prevents additional pheremone release.

when a paired female is experimentally tethered so that she cannot interact with her partner, the amount of time he spends releasing sex pheromones increases. therefore, male buying beetles may not be monogamous by choice. the monogamy is female-enforced.

Question 15

explain mate assistance in starling birds.

Answer 15

starling birds are bi-parental and the male helps incubate the eggs too. eggs that are incubated by both parents were kept at higher temperatures than eggs incubated by single parents, allowing for better egg development. therefore, the presence of males may be beneficial to childcare.

Question 16

in starlings, males help incubate the eggs. what trait of males is indicative of reproductive success?

Answer 16

males with LOW testosterone levels provided mroe food for their brood and had the highest fledging rates per brood. indicates that paternal care boost reproductive success in monogamous spotless starlings.

Question 17

T/F seahorses are monogamous

Answer 17

true.

Question 18

explain monogamy in djungarian hamsters

Answer 18

they align with the mate assistance hypothesis; being monogamous enhances reproductive success by protection/paternal care/resources combined with 2 parents.

hamsters are monogamous and the males actually help deliver their partner’s pups. they exhibit paternal care. Monogamous males have more offspring than single parent hamster systems.

Question 19

explain polyandry in red phalaropes (birds)

Answer 19

females have bright colors which attract multiple males, who all take care of raising her chicks. females are also larger.

Question 20

explain polyandry in jacanas

Answer 20

in polyandrous jacanas, females FIGHT FOR TERRITORY that can accommodate several males. males are forced to share reproductive output of the female with other members of her harem. and they may not even be the fathers of all of the female’s eggs they receive.

Question 21

polyandry is ____ for females and ___ for males

Answer 21

beneficial for certain species females and costly for males.

Question 22

3 factors that induce MALE monogamy in spotted sandpipers (polyandry)

Answer 22

1) males are way more common.
2) they nest in areas with immense mayfly hatches, leading to a LOT OF FOOD
3) young are precocious: a single parent can care for the kids nearly as well as two parents.

females who desert their first clutch of eggs and find new ones do not harm the survival of their first batch of offspring.

Question 23

indirect benefits of polyandry

Answer 23

females can derive potential GENETIC benefits from mating with many males, particularly for their offspring.

Question 24

4 hypotheses to explain the genetic benefits that females receive from being polyandrous

Answer 24

1) good genes hypotheses
2) genetic compatibility hypothesis.
3) genetic diversity hypothesis
4) inbreeding avoidance hypothesis

Question 25

explain the good gene hypothesis to explain polyandrous mating and provide an example

Answer 25

females mate polyandrously to produce offspring of higher genetic quality or viability.

ex/ yellow toothed cavy.
males have large testes, indicate intense sperm competition due to a high frequency of multiple mating by females. Females have more surviving babies if she mates multiply.

ex/ fairy wrens.
female fairy wrens live on a territory with a dominant male and a number of auxillary males, who HELP. in the morning, the female leaves the territory and seeks out copulations with dominant males on other territories.

Question 26

explain the genetic compatibility hypothesis to explain polyandrous mating and provide an example

Answer 26

females mate polyandrously to increase the odds of receiving genetically complementary sperm.

ex/ pseudoscorpions
females who mate with multiple males have more reproductive success ( live offspring); indicates that there is a heightened chance of sperm complementarity.

females who mate with multiple males have LESS EMBRYO DEATHS. this isn’t because the male’s sperm were duds, it’s because some male’s sperm were a better match for a female’s reproductive tract than others. the reproductive tract thus acts as a GENETIC SCREEN.

Question 27

explain the genetic diversity hypothesis to explain polyandrous mating (indirect benefit) and provide an example

Answer 27

females mate polyandrously to increase the heterozygosity of either individual offspring or of the group of offspring

ex/ honey bees.
queens that mate with multiple drones create larger combs than queens that mate and produce a colony with only one drone.

Question 28

explain the inbreeding avoidance hypothesis to explain polyandrous mating (indirect benefit) and provide an example

Answer 28

in the context of mating, females mate polyandrously to avoid inbreeding with their social partner.

ex/ red-backed fairy wrens.
females don’t mate with the males on the territory they live on, rather, they fly to other territories and copulate with the new males.

Question 29

in superb fairy wrens, a major component of the fitness benefits gained by females through extra pair copulations could be the production of sons that are so attractive that they repeat the extra-pair success of their fathers. this is known as the ___ ___ hypothesis

Answer 29

sexy son hypothesis.

Question 30

explain polyandry in the norwegian bluethroat.

Answer 30

in bluethroats, extra-pair offsprings were MORE HETEROZYGOUS (genetic diversity benefit hypothesis) than those sired by the female’s social partner. they also had a stronger immune system ( had more wing-swelling response)

Question 31

3 hypotheses to explain the DIRECT benefits to females engaging in polyandry

Answer 31

1) additional resources hypothesis
2) additional care hypothesis
3) infanticide reduction hypothesis

Question 32

explain the additional resources hypothesis that describes the direct benefits of female polyandry

Answer 32

females mate polyandrously to gain access to additional resources from their partner.

ex/ megachilid bee. by mating with many males, females of this bee species gain access to pollen and nectar in those male’s territories.

Question 33

explain the additional care hypothesis that describes the direct benefits of female polyandry

Answer 33

females mate polyandrously to gain more caregivers to help rear young

ex/ dunnocks
females living in a territory with two males solicit copulations more often from the male that has spent LESS TIME with them, whether that is the alpha or beta male. the benefit of distributing her copulations between two males is that she gets help from two males raising the kids.

Question 34

explain the infanticide reduction hypothesis that describes the direct benefits of female polyandry

Answer 34

females mate polyandrously to create greater uncertainty about the paternity of the offspring in order to reduce the risk of infanticide.

ex/ langurs usually commit infanticide when a new male becomes dominant. they will not kill the baby if there is a possibiltiy that its his.

Question 35

what is the most common mating systemin nature

Answer 35

polygyny

Question 36

4 hypotheses to desribe why males are polygynous

Answer 36

1) female defence polygyny hypothesis
2) resource defence polygyny hypothesis
3) lek polygyny hypothesis
4) scramble competition polygyny hypothesis.

Question 37

explain female defense polygyny hypothesis to describe why males are polygynous.

Answer 37

when resources are evenly distributed in space but females form groups to better access those resources or help dilute the risk of predation, males will follow and guard a group of females.

ex/ a large male spear-nosed bat guards a rooting cluster of smaller females.

Question 38

how to amphipods engage in female defense polygyny?

Answer 38

males glue a bunch of female houses to his shell so he can defend many females at once.

Question 39

how do montezuma oropendola birds engage in female defense polygyny?

Answer 39

male montezumas attempt to monopolize females in small colonies, but as colony size increases, mating attempts are disrupted.

Question 40

explain resource defence polygyny hypothesis to describe why males are polygynous.

Answer 40

when resources are clumped and attract multiple females and are easily defensible, males will guard these resources, and by extension, the females that are attracted to these resources.

ex/ male australian antlered flies will compete for possession of egg-laying sites on certain species of recently fallen trees.

Question 41

explain resource defence polygyny in cichlid fish

Answer 41

females lay their eggs in empty snail shells. males thus collect empty snail shells and then watch over them (watch over resources) that females are looking for, providing nest sites to females.

Question 42

explain lek polygyny hypothesis to describe why males are polygynous.

Answer 42

when resources are distributed heterogenously and females are widespread and do not form groups, males will wait for females to come to them. (males do not help with offspring raising at all)

the male’s territory does not contain valuable resources or food, there is little value except the male’s sperm itself.

huge inequalities in male mating success are typical of leks; some males are way more successful than others. different females may prefer the same male.

Question 43

explain lek polygyny in Topi deer

Answer 43

topi males tries to occupy a central position of his small territory. males in a central position at his lek mates with more females than males at peripheral sites.

Question 44

T/F in male hammer head bats, which are lek species, males actually have a pretty equal mating amount

Answer 44

false. male hammer headed bats cluster in dense groups at mating arenas where they defend central territories in trees overhanging riverbanks.

just 6% of males accounted for 80% of the matings.

Question 45

3 hypothesis to explain why males congregate in leks

Answer 45

1) hotspot hypothesis
2) hotshot hypothesis
3) female preference hypothesis.

Question 46

what is the hotspot hypothesis that explains lek congregation? example

Answer 46

males cluster in places called hotspots where the routes are frequently travelled by receptive females

ex/ sage grouse. lek location in sage grouse tends to be close to high densities of nesting females.

Question 47

what is the hotshot hypothesis that explains lek congregation?

Answer 47

subordinate males cluster around highly attractive males to have a chance to interact with females drawn to these “hotshots”.
ex/ black grouse.

Question 48

evidence against the hotspot hypothesis for lek congregation

Answer 48

1) the shifts in preferred territory over 5 years in black grouse suggest that MALE ATTRACTIVENESS (HOTSHOT) is more important than hot spot.
2) in Kafue Lechwe deer, female density is not correlated with lek location. this provides evidence AGAINST hotspot hypothesis because the leks are not in well travelled areas.

Question 49

explain the female preference hypothesis to explain lek congregation

Answer 49

the ideas that males cluster because females prefer sites with large groups of males where they can more quickly or more safely compare the quality of many potential mates (nature’s version of tinder).

ex/ in Bustards, females will visit groups of males when there’s 4 males than smaller or larger groups of males.

Question 50

male mating systems are an evolved response to :

Answer 50

female mating systems, and to the ecological factors that determine the spatial distribution of females.

Question 51

what is the scramble competition polygyny hypothesis to explain polygyny in males?

Answer 51

when resoures are distributed heterogenously and females are widespread and DO NOT form groups, males will seek out females (kind of opposite to lek)

males will “scramble” to find receptive females before other males do.

Question 52

explain scramble competition polygyny in 13-lined ground squirrels.

Answer 52

13 lined ground squirrel males can tell when a female is about to go into estrous. males remember the locations of females that are about to become sexually receptive.

the first male to find an estrous female and copulate with her will father about 75% of the pups. This is known as a FIRST MALE ADVANTAGE.

Question 53

explain scramble competition polygyny in male wood frogs

Answer 53

male rood frogs grasps a female he has found before rival males can get to her.

Question 54

polygynandrous mating systems require:

Answer 54

males and females to form pair bonds.

seen in red winged black birds. males have lots of females on the territory, but the eggs on his territory have genes from neighboring males.

Question 55

when are promiscuous mating strategies most common?

Answer 55

in species without parental care.
ex/ seaweed flies. both males and females copulate hundred of times during their short three-week lifespan. females often first resist male copulations, but often acquiese to attempts. this is known as “convenience polyandry,” and she gets mated with many males.

this can result in sexual conflict.