Personality traits, reproductive behaviour and alternative mating tactics in male European bitterling, Rhodeus amarus

Abstract

Individual differences in behavioural traits may play a role in reproductive behaviour and it is likely that different personality types have different reproductive success across specific social environments. This suggests a role for sexual selection for personality types, including a link between behavioural traits and alternative reproductive tactics. While research on morphological differences between guarders (bourgeois males defending resources) and sneakers (males parasitizing the territories of bourgeois males) is well characterized, the role of personality in the adoption of alternative mating tactics has hitherto been largely ignored. We investigated individual behavioural differences in a sneaker‐guarder mating system using size/age-matched males of a small freshwater fish, the European bitterling (Rhodeus amarus). We predicted distinct behavioural responses by guarder and sneaker males that were consistent in different contexts, indicating the existence of behavioural syndromes associated with male mating tactic. No behavioural syndromes were detected in male R. amarus, despite ability of individual male bitterling to establish dominance, boldness and investment in sperm competition being relatively repeatable across three consecutive trials. Male aggression, though not repeatable, was negatively correlated with the number of ejaculations, indicating a trade-off between aggression and sperm loading. No association between the tendency of males to guard a territory and behavioural traits was found, despite a significant association between the tendency to guard and morphological and physiological traits, with higher relative testis size and more breeding tubercles in guarder males. Our data suggest male bitterling mating tactics are largely unconstrained by innate factors and likely to be the product of prevailing environmental and social conditions.