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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