Meeting Abstract

S10.10  Tuesday, Jan. 6  Temporal coordination of life cycle stages: An avian chronobiology perspective HELM, Barbara; Max Planck Institute for Ornithology, Seewiesen and Andechs helm@orn.mpg.de

Reproduction of long-lived animals is embedded into a recurring cycle of annual activities. Many studies provide evidence for close links between between the timing of breeding and other life-cycle stages, including effects of calendrical cues experienced during other stages, carry-over effects of nutrition or habitat quality, and preparations for subsequent activities. Taking a chronobiological approach, the present study addresses reproduction as a periodic event within the annual cycle with a focus on birds. A first part highlights the natural diversity of annual cycles, including allocation of time to different activities like reproduction versus regeneration or enhanced survival. A second part addresses inherited programs that underlie the scheduling of annual cycles in many seasonal breeders. To time their activities, most animals use predictive cues like photoperiod, but because schedules differ between species and habitats, implications of a given daylength depend on annual routine and local seasonality. Accordingly, the relationship between photoperiodic cues and breeding undergoes evolutionary adjustments. An underlying (circ)annual cycle of reproductive activation and regression, however, persists in various species even in complete absence of temporal information. Circannual cycles are synchronized, but not driven, by photoperiod. Using data from comparative studies of a songbird, the stonechat (Saxicola torquata), I demonstrate that its geographically distinct schedules are based on conspicuous, heritable differences in circannual organization combined with phase-specific action of photoperiod. A final part addresses the interplay between circannual programming and environmental factors along a spectrum from rigid to flexible timing.