Adult predation shapes the evolution of swimming performance in guppies (Poecilia reticulata)

Predation pressure plays an important role in shaping animal behaviour and physiology, driving prey species to evolve stronger escape strategies. Swimming performance is a key trait for many aquatic organisms to evade predation. It is therefore intuitive that increased predation pressure should select for faster swimming abilities when outswimming predators is a viable option for prey. However, experimental evidence allowing for a causal link between predation and the evolution of swimming performance is currently lacking. Here, we used artificial selection lines of guppies (Poecilia reticulata) based on predation survival to test the evolutionary relationship between predation pressure and swimming speed. We used a swim tunnel with incremental increase in water flow to test critical swimming speed. Our results show that predation-line females, but not males, outperformed those of the control-lines in critical swimming speed. We also found that in predation-line females the variance in critical swimming speed was reduced in comparison with control-line females, which is congruent with directional selection against slow swimming genotypes. This study provides experimental evidence for the evolutionary role of predation pressure in enhancing swimming performance and shaping behavioural adaptations in prey species.