Evolution of Animal Photoperiodism

Photoperiodism is the ability of organisms to assess and use the day length as an anticipatory cue to time seasonal events in their life histories. Photoperiodism is especially important in initiating physiological and developmental processes that are typically irrevocable and that culminate at a future time or at a distant place; the further away in space or time, the more likely a seasonal event is initiated by photoperiod. The pervasiveness of photoperiodism across broad taxa, from rotifers to rodents, and the predictable changes of photoperiodic response with geography identify it as a central component of fitness in temperate and polar seasonal environments. Consequently, the role of day length cannot be disregarded when evaluating the mechanisms underlying life-historical events, range expansions, invasions of novel species, and response to climate change among animals in the temperate and polar regions of the world.