Beschrijving
Individuals differ in their diel timing depending on their genetical background and the environmental conditions. Individuals differ consistently from each other (= chronotype) as there is variation in the internal drivers of the circadian clock and the pathways that lead from clock to the diel timing. This entrainment of the clock generates physiological and behavioural rhythms of 24 h. Additional variation comes from short-term responses to changed environmental conditions. Here, we study the causes and consequences of between- and within-individual variation in chronotype. In specific, we evaluated the effects of individual differences in clock, of abiotic and social effects as well as the fitness consequences that could affect the retention of variation. Using different animal tracking methods, we monitored and manipulated activity patterns of wild great tits in winter and during the breeding season. As causes for variation we identified plastic responses to environmental factors such as season, weather, conspecifics and artificial light. Nevertheless, individuals had consistent and repeatable chronotypes, especially when using activity onset, but this individual consistency was unrelated to the individual differences in their internal clock’s speed. Additional variation between individuals might arise from other components of the entrainment pathway than the clock’s speed, i.e. cue perception and clock flexibility. All combined generate the consistent individual differences observed. Further research is needed to fully explore the individual variation that might be crucial for species to adjust and adapt to the anthropogenic fast-changing world. Contrary to our expectations, when assessing consequences of variation, we found that females with different chronotypes showed no differences in reproduction success. However, when exposed to artificial light at night, they had lower body weights indicating physiological costs of disrupted rhythms. Overall, this study contributes to understanding variation in diel timing indicating complex clock-chronotype pathways and an adaptive value of timing but not chronotype.| Periode | 22 feb. 2024 |
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