Personality, sperm traits and a test for their combined dependence on male condition in guppies

Abstract

There is evidence that animal personality can affect sexual selection, with studies reporting that male behavioural types are associated with success during pre- and post-copulatory sexual selection. Given these links between personality and sexual traits, and the accumulating evidence that their expression can depend on an individual's dietary status (i.e. condition), a novel prediction is that changes in a male's diet should alter both the average expression of personality and sexual traits, and their covariance. We tested these predictions using the guppy Poecilia reticulata, a species previously shown to exhibit strong condition dependence in ejaculate traits and a positive correlation between sperm production and individual variation in boldness. Contrary to expectation, we found that dietary restriction-when administered in mature adult males-did not affect the expression of either behavioural (boldness and activity) or ejaculate traits, although we did find that males subjected to dietary stress exhibited a positive association between sperm velocity and boldness that was not apparent in the unrestricted diet group. This latter finding points to possible context-dependent patterns of covariance between sexually selected traits and personalities, which may have implications for patterns of selection and evolutionary processes under fluctuating environmental conditions.

Keywords: animal personalities; behavioural syndrome; multivariate selection.

Figure 1.

Correlations (r) for each pairwise combination of traits (boldness, activity, sperm number and sperm velocity) within each diet treatment, calculated using multivariate mixed-effects models in ASreml-R. Bars represent approximate 95% confidence intervals. Dotted horizontal lines are at r = 0. r and approximate 95% CIs are bounded at −1 and +1.