Maternal investment influences development of behavioural syndrome in swordtail fish, Xiphophorus multilineatus

Despite a rising interest in behavioural syndromes (correlations between different behaviours across context and time), the development of these syndromes is not well understood. Using the swordtail fish Xiphophorus multilineatus, we looked at the effects of maternal investment and social environment during development on the formation of a behavioural syndrome. A previous study demonstrated that the diet on which mothers were reared, controlling for their size, influenced the growth rate and size of their sons: females reared on high-quality diets had sons that grew faster and were larger at sexual maturity. In addition, males that were exposed to an adult male during development grew faster. We examined the behaviours of these same males across two contexts: aggression towards a mirror image and boldness under threat of predation. We detected an influence of maternal investment but not of social environment on the formation of a behavioural syndrome. The sons of mothers reared on high-quality diets exhibited a positive correlation between boldness and aggression, while there was no correlation among the sons of mothers reared on low-quality diets. Maternal investment influenced the formation of the syndrome by producing changes in only one of the behaviours, the behaviour most closely linked to energy acquisition (boldness under risk of predation) rather than energy expenditure (aggression). Our results suggest that energy balances could help predict the circumstances that would favour the formation of behavioural syndromes. Our results also support the hypothesis that behaviours involved in energy acquisition as compared to energy use will be more sensitive to fluctuations in variation in resources.