Alternative reproductive tactics shape within-species variation in behavioural syndromes

Multiple behaviours can correlate with each other at the individual level (behavioural syndrome), and behavioural syndromes can vary in their direction between populations within a species. Within-species variation in behavioural syndromes is predicted to be associated with alternative reproductive tactics (ARTs) which evolve under different selection regimes. Here we tested this using a water strider species, Gerris gracilicornis, in which males employ two ARTs that are fixed for life: signalling males (producing courtship ripples) versus non-signalling males (producing no courtship ripples). We measured multiple behaviours in males with both of these ARTs and compared behavioural syndromes between them. Our results showed that signalling males were more active and attempted to mate more frequently than non-signalling males. This shaped an overall behavioural syndrome between activities in mating and non-mating contexts when we pooled both ARTs. In addition, the behavioural syndromes between cautiousness and mating activity differed significantly between ARTs. In signalling males, the syndrome was significantly negative: signalling males more eager to mate tended to leave their refuges more rapidly. However, mating activity and cautiousness were not correlated in non-signalling males. This might be because active males, in the context of predation risk and mating, were favoured during the evolution and maintenance of the unique intimidating courtship tactic of G. gracilicornis males. Thus, our findings suggest that ARTs facilitate behavioural divergence and also contribute to the evolution of tactic-specific behavioural syndromes. We also show that research on ARTs and behavioural syndromes can be harmonised to study behavioural variation.