Chapter 13: Mating Systems Flashcards
monogamy
1 male 1 female
polygyny
1 male, multiple females
polyandry
1 female, multiple males
polygyandry
plural breeding, multiple males and females with some social associations
promiscuity
multiple males and females, no social associations
sexual conflict
differential selection on males and females to maximize their fitness
female fitness is limited by access to resources to invest in offspring
male fitness is limited by access to mates/females
Emlen and Oring Model
describes when to expect the different mating systems
uniform to clumped, female to male biased care.
monogamy- if female’s partner offers high resources and parental care. uniform or clumped and mid bias. favoured if resources are poor and predation is high.
polyandry- clumped, male biased care
polygyny- resource/female defence if clumped, male dominance if uniform.
females aggregate to lower predation risk and male harassment while having resource access.
why might females gather
avoid predation
avoid male harassment
get resource access
resource defence polygyny
male defend a territory that attracts females
female defence polygyny
male monopolize resources and defend females due to resources
male dominance polygyny
(leks)
males advertise to females in a group
promiscuity
not really on graph. can be male or female biased care, cant predict. theres low benefit to social living so they dont stick together.
warbler E+O model approach/methods
comparative analysis, examine related species’ mating systems.
warbler E+O research question
how does habitat quality correlate with mating system?
how are habitat quality and mating systems related to level of male care?
warbler E+O model methods
create phylogeny
estimate habitat quality
characterize relative male care for offspring
warbler E+O results
poor habitat: monogamy, high parental care
medium or good habitats: polygyny, promiscuity and reduced male care
cali mouse observation
cali mice are monogamous (rare for mammals)
cali mouse research question
how does male care affect reproductive success in this species?
cali mouse prediction
reproductive success will be low if paternal care is absent
cali mouse methods
capture adults
check females for reproductive condition
remove males from monogamous pair within 3 days of litter birth
estimate # young born by comparing mother weight loss between last days of pregnancy and first capture since birth
compare offspring number and success (emergence from burrow) to control pairs with males
cali mouse results
both groups had similar # young
litters with no father had much lower success
cali mouse conclusion
male care enhances reproductive success in monogamous mice
shrimp monogamy research question
why are shrimp monogamous when the males provide no care?
territorial cooperation hypothesis
2 individuals (one of each sex) can better defend a critical resource
mate guarding hypothesis
a single male can benefit from remaining close to single female during reproductive cycles
shrimp monogamy predictions
pairs will better defend resource
males will most often guard females close to sexual receptivity
shrimp monogamy methods
allowed single females and paired females to guard burrow from intruder (same size/sex)
allowed males to choice females close to or not close to sexual receptivity
shrimp monogamy results
females paired with male were more successful in burrow defence
males chose to guard sexually receptive females more often
shrimp mate research question
how are males able to determine female sexual receptivity
shrimp mate methods
Y tank
1 arm normal water
1 arm treated
(had shrimp, then had pre/post/inter molt females)
shrimp mate results
males only moved to water with pre molt female
shrimp mate conclusion
males were able to determine female sexual receptivity and are attracted to them
territorial competition and mate guarding have favoured monogamy in shrimp
horse observation
feral horses live in bands with 1 male and up to 12 females
horse research question
do males defend females directly or the resources the females want?
horse methods
record location of bands for 3 years
record social behaviours especially aggression between males of different bands
plot home range of each band
horse results
bands overlapped so much, there was no defence of territories, the males fought over female access.
horse conclusion
males seem to display female defence polygyny
blackbird observation
blackbirds exhibit variation in their mating system
blackbird research question
why do some blackbirds mate monogamously, others polygynously?
blackbird hypothesis
polygyny threshold model. there will be variation in polygyny dependent on territory quality (or direct benefits)
blackbird prediction
polygyny should only be observed in high quality territories
how do female blackbirds nest?
they nest in dense vegetation around ponds. they mate monogamously or polygynously
blackbirds methods
females could mate monogamously in low quality territory or polygynously in high quality territory.
Add nesting platforms over water (high quality territory) for polygynous male
nesting platforms over land (low quality) for monogamous male
blackbird results
majority chose to mate polygynously on high quality territory.
blackbird conclusion
territory quality affects observed mating system, as predicted by polygyny threshold model
carrion beetle observation
males defend small vertebrate carcasses and females larvae feed on it. observe male-male aggression but not female-female over carcass.
carrion beetle research question
does the variation in aggression between sexes indicate that these beetles exhibit resource defence polygyny?
carrion beetle methods
place 2 males and 2 females next to meat
within each sex there was variation in size.
large males dominant over small
females mated with both males
record mating success via DNA analysis
carrion beetle results
large males had much more reproductive success
females had similar success with a slight edge to larger one
carrion beetle conclusion
resource defence polygyny is the mating system, males defend carcasses to keep smaller males away
lek
communal display ground where males showcase their secondary sex characteristics to impress females. there is usually a male dominance hierarchy on these leks
2 hypothesis to explain aggregation on leks?
hotspot hypothesis: males benefit by aggregating on leks where female encounter is more likely
hotshot hypothesis: males benefit by aggregating on leks were high quality males are, that attract females
great snipe observation
males display on leks for several hours each evening
