The first critical feature of circannual timekeeping is its predictive power to anticipate and prepare for upcoming seasonal changes in the environment. In a highly seasonal habitat, where changes in food supply and other selective pressures can be predicted through photoperiod, the timing mechanism allows for very precise regulation of the timing of cycles in physiology and behaviour. The anticipatory mechanism allows timing to be planned much in advance of the ecological events that ultimately determine survival and reproductive success. Second, circannual timekeeping allows organisms to express robust annual cycles which at specific phases override the effects of proximate cues, including photoperiod. Species differ in their responsiveness to immediate environmental conditions relative to reliance on internal timekeeping mechanisms. Reliance on endogenous features safeguards against being misled by untimely cues, such as unseasonal weather, but this advantage must be carefully balanced against benefits of direct responses to the environment. Finally, there is an increasing awareness that circannual biology is of economic and medical relevance to humans. Increasing our understanding of annual cycles in farm animals, family pets and wild species is required to help answer many animal welfare and conservation issues. This is of major current interest because of concern about the unknown impact of rapid climate change, for example, the worrying effects of increasing temperature on the ecology of insects Barbara Helm and Gerald A. Lincoln, 2017 Circannual Rhythms Anticipate the Earth’s Annual Periodicity *********************************************** The BEE-L mailing list is powered by L-Soft's renowned LISTSERV(R) list management software. For more information, go to: http://www.lsoft.com/LISTSERV-powered.html