Lectures 7, 8, and 9 Flashcards
Define socially monogomous
they pair with one mate, but might be genetically polyandrous
Define genetically polyandrous
when females “sneak” copulations outside their social pairing
What is the genetic mating system?
- may not be the same as the social mating system
- it is who you actually end up donating genetic material to (e.g., blue tits are a socially monogamous species, but 40% of the offspring come from “another man” )
Define promiscuity
the lack of any kind of social mating system, no social pair bonds.
Define monogamy
one male paired with one female. Socially, this means exclusive pair bonds. Genetically, this means that a pair exclusively reproduces with each other.
Define polygyny
males have multiple female partners, socially or genetically
Define polyandry
females have multiple male partners, socially or genetically
Promiscuity is the absence of a social mating system, which means…
- there are no ‘pair bonds’
- the individuals have multiple genetic partners. Socially promiscuous systems are often genetically polygynous
- since there are no male investment, the bulk of investment is carried by females
How does promiscuity evolve?
When the male benefits by leaving, rather than guard his mate and help with the offspring
What is an example of a promiscuous animal? What do they participate in?
Horseshoe crabs - participate in explosive breeding (meet in one spot, breed, and return to water)
What is the ecological driver of explosive breeding?
Predator satiation - predators can’t get them all if they all breed at the same time.
When can promiscuous systems arise?
Only when there is little reason for the pair to stick around each other
What is a lek?
a traditional location where multiple males display for females, waiting to be selected by a female.
What is an explosive lek?
A lek, but when lekking locations are dispersed a little more.
What is involved in lekking?
- genetic polygyny (some males mate with more than one female)
- extreme mating variance
-minority males get the majority of mating opportunities - ## female choice
What kinds of populations does lekking evolve in?
- populations whose females are widely dispersed enough that males cannot control a group of females
- populations whose offspring does not benefit from male parental investment
What is shown by the sage grouse example?
mating success in males has high variance. A few males mate with many females, while quite a few males have little to no copulation
-typical of lekking species
What are the three hypotheses for the questions: Why do leks form? Why don’t males display on their own?
- hotspots
- hotshots
- female preference
What is the hotspots hypothesis?
the males simply go where the females are.
- there isn’t great support because lek locations tend to wander a bit, which doesn’t support the idea that females congregate at a location for reasons other than lekking.
What is the hotshots hypothesis?
The idea that the hottest guys attract the most attention, so less superior males will congregate around them to get peripheral attention. An extension of satellite behaviour.
- E.g., Crickets —— satellite males (who do not call to females) hang out around calling males, they intercept the females as they respond to the calling male.
- has some evidence to support it (in snipes, if you remove the sexiest male, then the lek will center around somebody else)
What is the female preference hypothesis?
Females prefer to visit large groups of males (girls don’t want to go to a party if it’s not bumpin).
- If true: see positive relationship between the number of males and the number of responding females
- BUT: 1 to 1 ratio is not advantageous to either sex. In order for this to attract females, there needs to be an accelerating relationship, a curvilinear relationship.
True in Ruff’s graph
Not supported in Kobs graph
What does monogamy mean in both socially and genetically?
Socially: when one male is bonded to one female (fairly uncommon)
Genetically: pairs are exclusive sex partners
Define serial monogamy
moving from one monogamous relationship to another, but only being paired to one individual at a time.
In what type of animals is monogamy the main system for?
birds, some primates (humans are fairly monogamous), and termites
Define mutual mate choice
both males and females are choosy to some degree
What is an important feature to monogamous systems?
Compatibility - if you’re sticking with one individual, behavioural and genetic compatibility is key
What happened in the Oldfield mice experiement?
- a male is given two young females, and given the opportunity to choose one.
- when they were allowed to be with the female of choice, they had more reproductive success
- a new male, presented to those two females again, did not choose the previously preferred female significantly more than the other, suggesting mate choice is more about compatibility than simply choosing the superior mate (what is compatible for one male does not necessarily mean his mate would be preferred for all males)
What happened in the Puerto Rican Parrot experiment?
- an endangered parrot species
two facilities in PR aimed at rejuvenating the parrot population
-one facility paired males and females for “optimum” genetic diversity
-the other facility allowed the parrots to choose their own mate (the parrots that were allowed to choose their own mates had more than twice the reproductive success as those at the other facility. )
Define dimorphism
occurring in or representing two distinct forms
Define mutual assessment
individuals assess both themselves and their competitors - the loser gives up the contest when it has assessed that it is competitively inferior
Why would a male choose monogamy if given the choice?
- because according to the Bateman gradient, voluntary male monogamy is non-adaptive
- males tend to stay with their mates when the costs to finding another mate outweigh the benefits
What is mate-guarding?
a male staying near a female for a while after mating to guard their mate against extra-pair copulations
Explain the idea of females enforcing monogamous systems
- this can happen when females do not tolerate other females
- it might benefit the male to acquire another mate, but his female might fight off the new female
- sharing a male between females will result in less resources for each female
What is an example of females enforcing monogamous systems?
If you tie down a male burying beetle’s mate. he will “call”, emitting pheromones to draw her attention. Usually his mate will stop him from calling by showing up, but if she doesn’t come, he will continue to call, drawing other females. The presence of his female prevents him from calling other females.
Define synchronous breeding
when breeding happens at roughly the same time in a population
When does polygyny occur?
When some territories are significantly better than others, and becoming the second or third female on an area is better than being a single partner on a territory
What does the pair-bond duration data show?
Barnacle geese choose to stay together for a long time. The graph shows that individuals who stay with their mate longer have greater lifetime reproductive success.
- pairs who stay together rarely lose resources
What is a divorce?
When a pair could stay together, but have chosen to split
- it’s been found that birds do this opportunistically, moving to a better territory if the chance arises (another female dies)
What is EPC?
extra-pair copulations
What is EPF
extra-pair fertilizations
What can EPC result in?
EPF
What do EPF’s do?
introduce reproductive variance, increasing sexual selection pressure even in a socially monogamous species
What is Lesser gray shrike?
- if you take a paired female and hold her for a while, her male will beat her up when she returns ro their territory
- so males are clueing in to the fact that females seek out EPCs
Why doesn’t it make sense for females to seek EPCs, according to the Bateman Gradient?
There are costs to EPCs
- time
- effort
- risk STDs
- risk punishment from their male
Why do females seek EPCs?
females might keep the resources from her mate but seek out better genes from another male
Why might females pursue EPCs?
EPC increases probability of reproduction
-Gunnison’s prairie dogs (females who mate with more males are more likely to reach maximum reproductive viability - you’re ore likely yo become pregnant if you’re having sex with more males, as a sort of fertility insurance)
Why might females seek EPCs?
To divide paternal responsibility (“hot guys might not be good dads”)
- she might socially bond to the best “father”, but seek better genetic material from a different male
How might EPC allow females to attain better genes?
- might be pursuing outbreeding, increasing heterozygosity
- a degree of genetic diversity is preferred (pairings with diverse MHCs - major histocompatibility complex - means a stronger immune system in the offspring
- female starlings with lower heterozygosity to their mate (kind of inbred) tend to seek more EPCs from males outside of their social group
What leads to polyandrous/polygynous genetics in socially monogamous systems?
your mate’s behavioral compatibility does not equal your genetic compatibility
What is an indirect benefit of EPCs?
heterzygosity
What are some direct benefits of EPCs?
- female dunnocks allow EPCs when the second male provides her food
- female hanuman langurs have sex with multiple males so that each thinks her offspring is his and will not kill it. EPCs confuse paternity, avoiding infanticide
Define polygamy
any system where one individual mates with multiple individuals
Define social polygyny
some males are mated to multiple females
- some males because if some males have more than one mate, some males will have none
What does social polygyny lead to?
high reproductive variance in males
What are the 2 kinds of social polygyny?
- Female defense (AKA harem defense, it’s when one male defends a group of females)
- Resource defense (a male defends a resource that the female need, so they have to come to him
Define resource defense polygyny
males defend something the females want. Usually a place to breed
What is the polygyny threshold model?
the difference in fitness for a female when either monogamous or polygynous
- A graph based upon “should a female mate monogamously or polygynously?
- wherever she can get the best fitness
Explain the polygyny threshold model
- being the second female is bad…
- but being on a good territory is good…
- so some territories are so good that they make up for the costs to females of polygyny
- P1: fitness of monogamous and polygynous females is equal
- P2: improving mated males’ territories increases polygyny
- both predictions generally supported in birds
Explain female-defense polygyny
- occurs when females cluster together, usually for protection from predators (like elk do)
- males take advantage of these clusters and defend them from other males. In this case, the male isn’t defending the resources, but the clump of females themselves.
- In these systems, the females don’t have much choice other than accepting the male that is leading the harem
Define infanticide
killing babies
Why do males commit infanticide?
-make females sexually receptive again (occurs in species where the females raise the young and reproduction is limited to times when she is not caring for young) —-> offspring they kill is often not their own
Why do females commit infanticide?
- baby is not healthy
- the cost of raising offspring is too costly to the female due to environmental pressures
What kind of defense occurs in polyandry?
resource defense and mate defense
What type of polyandry is rare?
social polyandry
What type of polyandry is common?
genetic polyandry
What type of polyandry is very rare?
cooperative polyandry
Define cooperative polyandry
multiple males, one female, living cooperatively. Both males copulate with the female and raise the offspring together
- usually happens when resources are so scarce that one male is not enough to raise offspring
What is the trade-off in parental investment?
investing more in your offspring means investing less in future offspring
Why do females tend to young?
- higher investment in (future) offspring
- timing in internally fertilizing species
- certainty of parentage lower for males
- cost of not looking for more mates is higher for males
