Neuroendocrine control of seasonal phenotypic plasticity in birds

点击翻译按钮获取中文摘要

Most organisms exhibit seasonal changes in response to predictable changes in their environment. Seasonally-breeding songbirds show a tremendous degree of such plasticity. Birds adjust social behaviour, reproduction and movement across seasons. They exhibit high degrees of plasticity in the brain, reproductive physiology, and other systems. A bird's fitness depends critically on its ability to appropriately time seasonal changes in behaviour and physiology. A central theme of my research program addresses how birds use environmental cues to regulate seasonal changes in physiology, neurobiology and behaviour. *** The primary objective of my research over the next 5 years will be to explore the environmental physiology of seasonal changes in brain and behaviour. The primary hypotheses of this program include***1. Seasonality recapitulates ontogeny: the cellular mechanisms underlying brain development are regulated to induce seasonal neural plasticity.***2. Androgens, estrogens, and non-steroidal factors, have differential effects on seasonal neurogenesis and other forms of seasonal brain plasticity, and their effects will vary across different seasons.***3. Testosterone regulation, migration behaviour, and dispersal are correlated among individuals as part of a movement syndrome.***4. Endogenous clocks that are synchronized by photoperiod control the timing of migration, but gonadal androgens accelerate and synchronize spring migratory restlessness and inhibit fall migratory restlessness.***5. Responses to stressors such as predator cues and man-made toxins will vary seasonally.*** I will address the above hypotheses through a program of laboratory and field-based experimental studies. Using a suite of markers of developmental neural plasticity currently under development in my lab I will explore the similarities between seasonal and developmental mechanisms of brain plasticity by comparing brains from different times of year and following manipulation of hormones known to drive seasonal changes in behaviour. I will manipulate steroid hormones to determine how they control seasonal changes in brain anatomy. I will assess how gonadal steroids affect differences in migratory intensity and orientation between spring and fall migration using hormone removal and replacement experiments and monitoring behaviour in captivity and in the field using telemetry and remote tracking. I will test how brain responses to predator cues, and physiological responses to methylmercury change with the seasons.*** Combined, these lines of research create a uniquely integrative research program that explores how seasonal phenotypic plasticity is regulated. Specifically, I will explore how environmental factors affect seasonal changes in brain and behaviour via hormone signals, which is critical to predicting how birds will cope with changing environments.