W9L3 maiting system

Question 1

Why do we have mating system

Answer 1

• It is all about maximizing the survivorship of offspring
• If the young require care, and a singly parent cannot provide for the brood/clutch then might select for monogamy or cooperative breeding

Question 2

Ecology of sexual selection

Answer 2

1. Males compete with one another for access to females
2. Like competition for scarce resources, male reproduction is limited by the spatial and temporal availability of receptive females
3. The intensity of sexual selection depends on the rarity of receptive females in relation to the abundance of competing males
4. Sexual selection favours male attributes that permit their bearers to find and monopolize their mates
5. Ecological constraints on male monopolization attempts leads to a species-specific pattern of male-female association, called a ʻmating systemʼ

Question 3

What determines the spatial and temporal distribution of receptive females

Answer 3

• Abiotic factors: weather, latitude, seasonality
• Habitat and food availability
• Oviposition sites
• Species life history
• Genetic quality
• Other males and females

Question 4

Which gender control repoduction

Answer 4

Key decisions mainly controlled by females:
* Egg investment: what material and how much
* Mate choice: which males will donate sperm
* Fertilization: which sperm to use for each egg
* Offspring investment: how much maintenance and care to each embryo and offspring

Question 5

Male in reproduction control

Answer 5

• Resources transferred to females: may influence egg investment, mate choice, or fertilization
• Elaborate courtship: may influence mate choice and fertilization
• Sexual coercion: may overcome female preferences
• Infanticide: may overcome female decisions about offspring investment

Question 6

Sex differences in fitness variance for the evolution of mating systems

Answer 6

• Male variance in fitness is often > females
• Directly affected by the distribution of receptive females in space and time

Question 7

What influence the Classification of mating systems

Answer 7

• Based on number of mating partners and the number of reproductive events
• Influences the variance in mating success
• Impacts on the opportunity for sexual selection (Imates ) = variance in fitness of each sex/mean fitness for each sex

Question 8

Calculation for opportunity for sexual selection

Answer 8

Question 9

Important thing to remember for opportunity for sexual selection

Answer 9

We can measure the intensity of sexual selection from the spatial distribution of females
* The spatial distribution of females is only one component of the sex difference in the opportunity for sexual selection
* Other important factors are: sex ratio and temporal distribution

Question 10

Effect of sex ratio

Answer 10

• Influence the number of receptive females on a patch
• Hence directly influence the spatial distribution of females
• Stronger sexual selection when males are abundant

Question 11

Two components of variance in mating success exists when female are clumped in time

Answer 11

1. The variance in mating success within the class of males that actually mate by defending females
2. The variance in mating success among the mating and non-mating males

Question 12

The effect of opportunity for sexual success when clump in time

Answer 12

Question 13

Iteroparity

Answer 13

• Reproduce >once in successive years or breeding seasons
• Variation in number of clutches and number of offspring per clutch

Question 14

Monogamy

Answer 14

• Male and female pair mate only with one another during a single breeding season
• When both sexes are needed for successful reproduction
• Could also evolve as a paternity assurance for males = mate guarding
• Males often help in raising young

Question 15

Polyandry, polygyny and promiscuity

Answer 15

• Polyandry = females mate with >1 male during a breeding season
• Polygyny = males mate with > 1 female during a breeding season
• Promiscuity = both males and females mate with many partners during a breeding season

Question 16

The effect of monandry on Imates

Answer 16

• When a female mates once and produces only one clutch of offspring, she awards her entire reproductive output to a single male

Question 17

The effect of polyandry on Imates

Answer 17

When a female mates more than once, she partitions her clutch into several sub-clutches, equal in number to the number of sires

Question 18

Overall effects of polyandry on Imates

Answer 18

• Each mating male sires only a fraction of the offspring of each mate he secures
• The variance in mate numbers among males Is reduced

Question 19

The effect of iterparity on Imates

Answer 19

When a female produces more than one clutch, the variance in offspring numbers can be partitioned into within- and among-female components
* Multiple reproductive episodes by females erode I
* As clutch number increases, I becomes a smaller fraction of the total variance in offspring number

Question 20

Protandry as a male strategy

Answer 20

• Related to temporal distribution of females
• Males emerge before females
• Maximize no. of mating with virgin females
• Increased fertilization returns

Question 21

Leks courtship

Answer 21

• Leks are courtship arenas where males display
• Often involve intense male-male competition leading to a dominance hierarchy
• Dominance reflects male fitness and assessed by females

Question 22

Effect of predation; examples from guppies

Answer 22

• Predation varies among streams
• High predation males less colourful, court less and females less choosy
• Female mate copying reduce the cost of choice?

Question 23

Cooperative breeding and parental care

Answer 23

> 2 individuals care for the brood
* Variation in reproductive skew
* Habitat saturation?
* Increase survival of offspring?
* Low mortality and small clutch size
* Constant environments

Question 24

Sex role reversal; bushcricket example

Answer 24

• Males provide a lot of nutrients
• female feed on Pollen which availability varies
• Females in large nutritional need
• Male donations >female investment
• Result in sex role reversal

Question 25

Hermaphrodites

Answer 25

The condition of having both male and female reproductive structures
* Simultaneous hermaphrodites
* Sequential hermaphrodites; males first = protandry female first = protogyny

Question 26

Evolution of hermaphroditism

Answer 26

• Low population density –hard to find a mate
• Sequential – the sex where max returns for small/large size

Question 27

Alternative mating strategies

Answer 27

• Success is directly dependent on the strategy played by competitor

Question 28

Example: male polymorphism in
Paracereis sculpa

Answer 28

a-, b-, g-male morphs
* males control resources
* b- and a- males prefer to invade large harems
* large a- males can defend against other
a- males
* b-males are female mimics
* g-males are tiny and hide among females

Question 29

Alternative male tactics in lizards

Answer 29

Males have three mating strategies:
1. Territory holders, large, aggressive - several females (Orange)
2. Sneakers, mimic females, enter orange territories (Yellow)
3. Defenders, detect sneakers, defend small territories with one female (Blue)

Question 30

Alternative male tactics in scorpion flies

Answer 30

Question 31

Three male strategies

Answer 31

-equals fitness frequency dependent equilibrium
-cyclical dynamic
-not equal fitness

Question 32

Consequences of alternative mating strategies

Answer 32

• When the number of mating males increases, the mean number of mating per male, the variance in male mating success, and the opportunity for sexual selection all must decrease
• Thus, alternative mating strategies erode the sex difference in the opportunity for sexual selection