Lecture 9: Mating Systems Flashcards
Define ‘mating system’.
General behaviour strategy, or suit of behaviours and adaptations, employed in obtaining mates.
What limits a males reproductive success?
Availability of females.
What limits a females reproductive success?
- Their own fecundity
- Availability of resources.
What determines the intensity of sexual selection?
The variance in fitness (greater in males).
What equation can we use to determine the intensity of sexual selection?
Operational Sex Ratio (OSR) = No of receptive females/ No of sexually active males.
Define ‘spatial distribution’.
Organisms live in a clumped, patchy distribution.
Define ‘temporal distribution’.
Organisms live evenly spaced apart.
What is the relationship between opportunity for sexual selection and mean female spatial crowding?
Positive.
What is the relationship between opportunity for sexual selection and mean female temporal crowding?
Negative.
What is the Emlen and Oring Hypothesis?
Like competition for scare resources, male reproduction is limited by the spatial and temporal availability of sexually receptive females.
How can males increase their reproductive success?
- Increase number of mates
- Increase number of offspring they sire per mate.
How can females increase their reproductive success?
Increase their own fecundity (i.e. number of offspring per clutch and clutch numbers).
What is the Parental Investment (Triver’s) Hypothesis?
Sexual selection may be due to anisogamy (i.e. the size of gametes and the difference between the energy that goes into the gametes of the two sexes).
Define ‘polyandry’.
Males mate once; females are variable in mating numbers.
What are the costs of polyandry?
- Physiological harm
- Increased risk disease
- Increased predation risk
- Reduction in parental care.
What are the direct benefits of polyandry?
- Nupital gifts (e.g. nursery web spider)
- Fertility assurance (one male mate may be infertile)
- Increased parental care
- Convenience polyandry (submission to avoid harm).
What are the indirect benefits of polyandry?
- Trading up (females re-mate with partners of better quality)
- Genetic diversity (account for future environmental change)
- Good sperm (females re-mate with males with superior fertilising sperm which reflects male genetic quality)
- Sexy sperm (females re-mate with males to promote increased fertilisation efficiency arising from sperm competition)
- Genetic compatibility/ Inbreeding avoidance (females multiply mates to increase heterozygosity and avoid inbreeding).
Give examples of male adaptations for avoidance and engagement in sperm competition.
- Pre and post-copulatory guarding
- Biochemical barriers to remating
- Physical barriers to female re mating (mating plugs)
- Traumatic insemination (bed bugs)
- Sperm morphology and function
- Testes size and sperm production
- Copula duration
- Copulation frequency.
Define ‘monogamy’.
Each sex mates only once.
Define ‘polygyny’.
Females mate once; mates are variable in mate numbers.
Define ‘polygamy’.
Both sexes have variable mate numbers. Male mating success is approx = female mating success.
Define ‘polyandrogyny’.
Both sexes have variable mate numbers; female mating success is more variable than male mating success.
Give examples of monogamous species.
- Black-browed albatross
- Prairie vole.
What are the predictions of monogamy?
- Rare
- No or low opportunity for sexual selection
- Negligible sexual dimorphism
- No sperm competition
- No sexual conflict
- Male parental care.
