Coping with stress: personality, life history and social dominance in swordtail fishes, Xiphophorus sp.
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Date
27/11/2014Author
Boulton, Kay
Metadata
Abstract
Competition for resources plays an important role in natural selection, creating
winners and losers. Winners become socially dominant, obtain resources and so
increase their fitness at the expense of losers. Provided they are heritable, phenotypic
traits promoting competitive success will be inherited by subsequent generations.
Thus, while resource dependent traits (e.g. growth) that rely on competitive outcomes
are widely recognised as being under strong selection, this is also likely to be the case
for those traits that determine competitive ability and social dominance. In addition,
competition is expected to be an important source of stress, for example, harassment of
subordinates by dominant individuals. Consequently individual fitness may depend
not only on the ability to win resources, but also on the ability to cope with stress. This
thesis proposes that social dominance is not just a simple consequence of body size or
weaponry, but rather that the interplay between growth, repeatable behavioural
characteristics (i.e. personality), and the ability to cope with social and environmental
stressors are equally important factors. Thus the dynamic of dominance arises, a model
that highlights the expectation of complex relationships between traits causal and
consequent to social dominance. Here, empirical studies of Xiphophorus sp. are used to
test each element in the model. First the concept of individual personality is explored,
asking to what extent it is really stable over long periods of time (equivalent to lifespans).
Next, the links between behaviour, physiological stress and contest outcome
are considered and, using a repeated measures approach, the hypothesis that
individuals differ in stress coping style is evaluated. Finally, using a quantitative
genetic approach the additive genetic variance-covariance matrix (G) is estimated
between behavioural and life history traits under experimentally manipulated levels of
competition. In this way the contribution of genetic and environmental effects to the
patterns of trait (co)variation that make up the dynamic of dominance is assessed.