Evolution of alarm cues: a test of the kin selection

The evolution of alarm signals has puzzled evolutionary ecologists for decades. This is particularly true for alarm cues (‘Schreckstoff’) which are present in many fishes. They are passively released through injuries and signal the presence of a predator. Although the benefits for conspecific receivers are obvious (they can adjust their behavior to avoid predation), those for the senders are not which is, however, a necessary requirement for the evolution of alarm signals. Several hypotheses relying on potential direct benefits for the senders have been suggested. Alarm cues might attract secondary predators which in turn might increase the escape probability of the sender. A primary immune enhancing role was suggested as well. An alternative explanation is based on Hamilton’s inclusive fitness theory stating that individuals can indirectly increase their fitness by increasing the survival of genetically related individuals (‘kin selection theory’). If related individuals preferentially benefit from alarm signals, for instance by being more receptive to kin-alarm cues, senders could increase their inclusive fitness. Here, we investigate whether individuals of the cichlid fish respond differentially to Pelvicachromis taeniatus alarm cues derived from kin and non-kin. possesses alarm cues P. taeniatus and is known to adjust its behavior when exposed to alarm cues. We measured the change in activity after the addition of alarm cues (derived from kinand non-kin) relative to a control treatment. Reduced activity is a widespread behavioral adaptation to reduce predation risk in prey organisms. Fish of the alarm cue treatments significantly reduced their activity relative to control fish. However, fish did not respond differentially to alarm cues derived from kin and non-kin suggesting that potential inclusive fitness benefits are not mediated by responses specific to individual alarm cues. We discuss alternative mechanisms such as kin shoaling and mating preferences potentially leading to kin-biased alarm cue perception. Referee Status: