L11

Question 1

What does mating system classification encompass?

Answer 1

• Copulation behaviour
  
  • Social organisation
  • Parental care system
  • Competition for mates

Question 2

Monogamy

Answer 2

• Pair bond
  
  • Short or long time scale
  • Often both sexes care for young
  • Mostly birds
  • Rare in mammals

Question 3

Anenome fish

Answer 3

• No need for males to be larger to compete
  
  • No costs of large body size
  • All start off male

Question 4

Monogamy across Birds

Answer 4

• Variable rates of extra pair mating’s across birds
  
  • <25% of socially monogamous birds are also genetically monogamous

Question 5

Polygyny

Answer 5

• One male associates with several females
  • Few birds, most mammals
  • Essentially means males sequentially moves on to different mates

Question 6

Polyandry

Answer 6

• One female associates with several males
  • Same time or in succession

Question 7

Promiscuity (polyandry)

Answer 7

• Multiple females and males
  • Less common in birds and mammals
  • Some have no set paternity

Question 8

Does the mating system often vary within a species?

Answer 8

Yes

• Eg extra pair paternity in monogamous species
  • Eg dunnocks
  • Exhibit a variable mating system
• eg some humans, are man and wife and some are eg two brothers and one wife

Question 9

Reproductive potential and a general model

Answer 9

• Based on gametes males have a greater reproductive potential than females
  • Males are limited by access to females, females are limited primarily by access to resources

Question 10

General model

Answer 10

Expect female dispersion to be determined by the distribution of resources (Ecology)

- Male distribution is determined by female distribution (this is a mating system)

Question 11

Ecology and mating systems, what does a mating system depend on?

Answer 11

• Comparative study of mammalian mating systems
  • In mammals, male parental care is rare
  • Female monopolisation by males and hence mating system depends on:
  1. Female group size
  2. Female range size

Question 12

Solitary females

Answer 12

• Females with small ranges, are defendable by males
  • When range is larger, male can only defend a single female not multiple (monogamy emerges)
  • Range must be full of resources enough to survive

Question 13

Orangutans

Answer 13

• To gain enough food female needs to travel large distances
  • No single male can defend such a large area
  • Scramble competition occurs : males wander looking for fertile females they can associate with and mate during her fertile period

Question 14

Social females

Answer 14

• May confer defence benefits
  • Easier to find resources
  • Defendable by one male which can monopolise a large group of females
  • Pride of lions requires multiple males for defence
  • Sometimes single male defends small pride
  • Sometimes multiple males defend a larger pride

Large range not defendable

- Females live in large unstable groups

- Males lek 

- Females visit leks and then return after copulation

Question 15

Lek polygyny

Answer 15

• Females with large ranges cannot be defended by males
  • When female ranges are smaller, males can defend so have a larger range
  • Ecological factors determine range size

Male dispersion is dependent on female dispersion

Question 16

Does food distribution determine female dispersion? Experiment

Answer 16

• Range collapses when food provided as no need for it
  • Yes, but males also converged on food, this could be because they were after females or after food

Question 17

Experiment 2

Answer 17

• When females were clumped into small ranges, male ranges clumped around these
  • When females clumped into large ranges, male ranges were larger

Question 18

Experiment 3

Answer 18

• No effect of male dispersion on females

Question 19

Resource defence by males

Answer 19

• Tent-making bat
  • Females roost in tent
  • Small tent = few females to roost in
  • Resource opens opportunity to breed with roosting females

Question 20

• Once males provide paternal care, males become critical for females

Question 21

Is reproductive potential of males limited by care?

Answer 21

• Male reproductive rate

Sex role depends on potential reproductive rate, which in turn depends on relative provision of parental care

- Comparison of species with male-only care

- Females grow ornaments and become aggressive

- Sometimes males provide so much parental care, males have a lower reproductive rate, but sometimes not

Question 22

In 13 species, where males have a higher reproductive rate there was conventional roles

When females had a higher reproductive rate a sex role reversal ensued

Question 23

Sexual conflict over mating systems

Answer 23

• Extreme sexual selection
  • Males prefer polygyny
  • Females may prefer polyandry if they get more/ better resources
  • In many species, monogamy occurs as a compromise between conflicting interests of the sexes

Females raise more offspring in small groups

Males raise more offspring in large groups

More females = more resources so each female doesn’t do as well

Males do best when there are more females