Meeting Abstract
For birds resident to the North Temperate Zone, preparing for and surviving winter is considered one of the most difficult parts of the annual cycle. Previous work has documented that in response to cold winter temperatures, residents alter much of their morphology and physiology, including enlarging their pectoralis muscles, enhancing vascular oxygen transport, and upregulating portions of their fatty acid transport pathway. Nonetheless, the time course over which these changes occur remains unknown. For instance, do they all occur simultaneously in response to the onset of cold temperatures or are they made incrementally in response to increasingly long periods of cold? To determine the progression and rate at which individuals adjust their physiology in response to cold temperatures, we performed an acclimation experiment to assay a large suite of physiological parameters across time. We captured Dark-eyed Juncos, Junco hyemalis (n = 60), and, after a six-week adjustment period, exposed individuals to one of two temperature treatments (-8°C and 18°C) for up to 8 weeks. We quantified metabolic parameters and body composition before and after treatments for each individual. We also longitudinally assessed physiological parameters by terminally sampling 5 individuals/treatment at 1, 2, 3, 6, and 8 weeks and quantifying a suite of traits (e.g., blood-oxygen parameters, organ size, enzyme activities). Additionally, we collected tissues for transcriptomic assays to assess the time-scale on which regulatory changes are occurring. Our results shed light not only on the mechanisms underlying seasonal phenotypic flexibility, but also indicate how species may be able to cope with short-term extreme weather events, which are predicted to increase in frequency in the near future.
