Daphnia mitsukuri traits responding to predation cues alter its population dynamics

Abstract Individual traits responding to predation cues are widespread in many aquatic and terrestrial organisms. However, linking individual traits to population dynamics in response to predation cues is poorly understood despite its important role in shaping ecosystems. In this study, we investigated the individual traits associated with population dynamics of Daphnia mitsukuri in response to two different cues from fish predation. Two clones of D. mitsukuri were reared under alarm signal, kairomone, and their combination treatment until the populations reached maximum abundances. Individual inducible traits, grazing rates, and population parameters were recorded for the growing populations. Our data showed the population dynamics were highly correlated with the individual traits, and some mechanical correlations were discussed in the present study. Specifically, in the combination treatment, the decreased individual size contributed to enhancing the individual grazing rate at a high population density, which ultimately resulted in a higher (75%) maximum population density compared to the control. Besides, diversified links between individual traits and population dynamics were observed in different clones, especially in dormant egg production. In summary, inducible changes in individual morphological characteristics and life history traits were associated with variation in population dynamics of Daphnia in response to cues from predation. This study is helpful to understand the effects of signals of predation risk on the individual and population levels.