W3: Mating Systems Flashcards
Monogamy
(one marriage) both sexes have 1 mate.
Lifelong & serial
Polygamy
(multiple marriages) one or both sexes have more than one mate
Polygyny
(multiple females) some males have more than one mate; females have just one.
Polyandry
(multiple males) some females have more than one mate; males just have one
Promiscuity & Polygynandry
both males and females can have more than one mate
What type of mating is costly at the species level?
Multiple matings are costly at the species level.
Genetic benefits of polyandry
- Fertility insurance
- Good genes
- Genetic compatibility
Material Benefits: - More resources
- Better protection
- Infanticide reduction
Fertility Insurance Hypothesis
Mating with several males reduces the risk that some of the female’s eggs will remain unfertilized dues to mating with a partially or completely infertile male.
Good Genes Hypothesis
Females mate with more than one male because their social partner is of lower genetic quality than other potential sperm donors whose genes will improve offspring viability or sexual attractiveness.
Genetic Compatibility Hypothesis
Mating with several males increases the genetic variety of the sperm available to the females, increasing the chance that some will be genetically compatible with her eggs.
More Resources Hypothesis
More mates mean more resources or parental care received from the sexual partners of a female.
Better Protection Hypothesis
More mates mean more time with protectors who will keep other males from sexually harassing a female.
Infanticide Reduction Hypothesis
More mates mean greater confusion about paternity of a female’s offspring and thus less likelihood of losing offspring to insecticidal males.
How do Gunnison’s prairie dogs increase their probability of giving birth and increasing litter size?
By having multiple sexual partners
The Monogamy Paradox
Why would any male restrict his efforts to fertilizing just one female?
Answer to the Monogamy Paradox:
- Mate guarding: females are hard to find
- Mate assistance: extra offspring outweighs cost
- Female-enforced: females refuse to mate with already-mated male or chase off other females
What is the associated mating system in an environment where males are unable to defend more than one female?
Monogamy or promiscuity
What is the associated mating system in an environment where some males can defend more than one female?
Polygyny
How did scientists study female & male dispersion in grey-sided voles?
- grey-sided vole females clump around concentrated food resources
- females experimentally moved around led to males clumped when females clumped, males dispersed when females dispersed.
- males experimentally moved around resulted in no change in female dispersion
Polygyny Threshold Model
Fitness of second female sharing a male on high quality territory is equal to the fitness of female who nest monogamously on low quality territory.
What are some male mating strategies?
- Female defense
- Resource defense
- Scramble competition
- Lekking
Scramble Competition
Males don’t attempt to defend territories, rather they search for receptive females and try to mate with whomever then encounter.
Lekking
Defense of a traditional display site that females visit to select a mate from among the several to many males displaying on the small, resource-free territory.
Why do males cluster at leks?
- Hot spot: males cluster when encounter rates are high
- Hot spot: clusters form around attractive males
- Predator Dilution:males cluster for safety
- Female Benefit: females prefer to mate at particular sites or with males in clusters either for their personal safety or to compare males.
