Mating Systems

Question 1

1. Mating system classification

Answer 1

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

Question 2

<25% of socially monogamous birds are also genetically monogamous

Answer 2

Most birds, a few mammals and fish

Question 3

Polygyny

Answer 3

few birds, most mammals

Question 4

Polyandry

Answer 4

few birds, fish and mammals

Question 5

Promiscuity (polygynandry)

Answer 5

> 1 female and >1 male

Few birds, few mammals, many fish, reptiles and amphibians

Question 6

Mating system often varies within a species

Answer 6

e.g. Extra-pair paternity in monogamous species

e. g. dunnocks - monogamy
- polygyny
- polyandry
- polygynandry

Question 7

Reproductive potential

Answer 7

Male reproductive potential
> Female reproductive
potential

Males are limited
by access to females
Females are limited by access to resources

Question 8

Resource defence polygyny

- males defend key resources wanted by females

Answer 8

e.g. tent-making bats
Males construct and defend roosting tents which house harems of females
Sex ratio:
1 M : 1-37 F

Question 9

Ecology: Comparative study of mammalian mating systems
Clutton-Brock (1989)
In mammals, male parental care is rare

Answer 9

Female monopolisation by males, and hence mating system, depends on:
- Female group size - Female range size

Question 10

Blue-headed wrasse

Females
Forage over large overlapping ranges Spawn daily at predictable, favoured sites

Males
Can’t defend females
Compete for and defend spawning sites

Answer 10

Warner (1990) experiment

Removed males, replaced with new males
22/24 sites still used, no new sites

Removed females, replaced with new females
11 sites lost, 10 new ones

Question 11

Sexual conflict over mating system

Answer 11

Female and male make a nest containing a corpse, and then care for offspring.
Males attempt to attract additional females, females try to prevent them doing so:
Female enforced monogamy in burying beetles (Nicrophorus species)

Question 12

Males may compete directly to monopolise females or they may try to monopolise the resources that females need for survival and reproduction.

Answer 12

Males usually prefer polygyny and females may prefer polyandry over monogamy if they get better resources or good genes. This is especially likely to be true when males provide substantial paternal care and hence become an important resource for females that they do not want to share with another female.

Question 13

Therefore, in many species, monogamy occurs not because both sexes do best but because of conflict within and between the sexes.

Answer 13

For example, males compete for females and may be unable to defend >1 at a time. Alternatively, females may enforce monogamy on males.

Question 14

A lek is an aggregation of male animals gathered to engage in competitive displays, lekking, to entice visiting females which are surveying prospective partners for copulation.[1] Leks are commonly formed before or during the breeding season. A lekking species is characterised by male displays, strong female mate choice, and the conferring of indirect benefits to males. Although most prevalent among birds such as black grouse, lekking is also found in insects including paper wasps, crustaceans, fishes, amphibians, reptiles and mammals.

Answer 14

A classical lek consists of male territories in visual and auditory range of each other. An exploded lek, as seen in the kakapo (the owl parrot), has more widely separated territories, but still in auditory range.

Lekking is associated with an apparent paradox: strong sexual selection by females for specific male traits ought to erode genetic diversity by Fisherian runaway, but diversity is maintained and runaway does not occur. Many attempts have been made to explain it away,[2][3][4][5] but the paradox remains.