Lecture 11: Mating Systems

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APS209 Animal Behaviour - Mating systems

Aims

1. To present the concept of mating systems and the relative reproductive potential of the two sexes.

2. To illustrate the role of ecology and paternal care in determining mating systems
3. To demonstrate the prevalence of sexual conflict in mating system evolution.

 

Objectives

1. To understand a general model of mating system evolution
2. To understand the role of ecology and parental care in mating system evolution
3. To understand the basis for sexual conflict over emergent mating system and its outcome.

Mating systems
Includes description of: copulation behaviour, social organization, parental care system, and pattern of competition for mates. Results in monogamy, polygyny, polyandry, and promiscuity, but social mating system does not always reflect genetic mating system (e.g. extra-pair paternity in monogamous birds). There are consistent taxonomic differences in mating systems

Male and female reproductive potential and a general model
Male reproduction is limited principally by access to mates, while females reproduction is limited by access to resources. Therefore, we can construct a general model:

Ecology, e.g. resources,         ->         Female dispersion     ->      Male dispersion
predation, etc

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

Ecology and mating systems
The general model for the evolution of mating systems predicts that mating systems should reflect female dispersion and resource distribution. This model is supported by a comparative study of mammals by Clutton-Brock (1989, Proceedings of the Royal Society of London, Series B 236: 339-372). Mating systems from monogamy to lekking can be explained using just three female parameters: group size, range size and breeding synchrony.

Mating systems with male parental care
When males care for offspring, they become an important resource for female and his reproductive potential is reduced. The identity of the competing sex depends on relative reproductive rate (see Clutton-Brock & Vincent 1991 Nature 351: 58-60)

Most birds are socially monogamous with biparental care. However, monogamy is usually facultative rather than obligate. When one sex deserts, it is usually male because they have greater opportunity for desertion (internal fertilization), and more to gain (higher reproductive rate). In many cases monogamy results from limited opportunity for polygamy, due to competition among males and/or females.

Sexual conflict over mating systems
Males usually prefer polygyny and females may prefer polyandry over monogamy if they get better resources or good genes. Therefore, in many species, monogamy occurs not because both sexes do best but because of conflict within and between the sexes. For example, males compete for females and may be unable to defend >1 at a time. Alternatively, females may enforce monogamy on males.


Reading: see Chapter 11 in John Alcock’s Animal Behavior (2009: pp. 379-419); also Nick Davies’ chapter on Mating Systems in Krebs JR & Davies NB (eds) Behavioural Ecology 3rd edn, Blackwell.

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