Research Starter Grant

对环境中的应激事件作出反应对所有生物体来说都是一项根本上重要的活动。在应激反应中，糖皮质激素的作用是可塑性的，根据生活史策略、生殖阶段、身体状况甚至一天中的不同时间，允许在反应中具有特异性。这项建议探索了白冠麻雀三个亚种(Zonotrichia leucophrys Gambeli、Z.L.oriantha和Z.L.pugetensis)这种可塑性的机制、环境调节和功能后果。这三个亚种具有不同的分布，这可能会影响塑造应激反应的进化压力。特别是，这些麻雀在不同的海拔和纬度繁殖，因此繁殖季节在长度上有明显的差异。Gambeli是最北部的亚种，在北美洲的北极和亚北极地区繁殖。繁殖季节很短(每个季节只允许一只幼崽)。在美国西部亚高山草甸中繁殖的冬凌草。他们每个赛季可以养一只，有时两只。普吉特在太平洋西北部的低海拔地区繁殖，通常每个季节饲养2到3只幼崽。这项建议探索了繁殖季节的长短对鸟类如何应对压力的进化影响很大的可能性。具体地说，对于只有时间养一只或很少养两只幼崽的鸟类来说，放弃巢的健康后果可能比每个季节最多养三只幼崽的鸟类的健康后果要大得多。因此，繁殖季节短的动物应该对应激源反应较小，因此不太可能遗弃它们的幼崽。每个亚种的应激反应将通过测量基础的和应激诱导的皮质类固醇对捕获和处理的反应、皮质类固醇结合球蛋白水平(以估计糖皮质激素的生物利用度)和糖皮质激素受体水平(以估计组织对糖皮质激素的特异性敏感性)来评估。

Responding to stressful events in the environment is a fundamentally important activity for all organisms. Within the stress response, there is a plasticity of glucocorticoid action, allowing for specificity in the response depending on life history strategy, reproductive stage, body condition, or even time of day. This proposal explores the mechanisms, environmental regulation, and functional consequences of this plasticity among three subspecies of the white-crowned sparrow (Zonotrichia leucophrys gambelii, Z. l. oriantha, and Z. l. pugetensis). The three subspecies have different distributions that are likely to affect the evolutionary pressures shaping the stress response. In particular, these sparrows breed at different elevations and latitudes and thus have breeding seasons that differ markedly in length. Gambelii is the northern-most subspecies, breeding in the arctic and sub-artic regions of North America. The breeding season is short (allowing only 1 clutch per season). Oriantha breed in sub-alpine meadows of the western United States. They can raise one and sometimes two clutches per season. Pugetensis breeds at low elevations in the Pacific Northwest and usually raises 2 or 3 clutches per season. This proposal explores the possibility that the length of breeding season has a strong evolutionary influence on how birds respond to stress. Specifically, in birds with time to raise only one or rarely two clutches, the fitness consequence of abandoning the nest may be substantially larger than in birds that can raise up to three clutches per season. Thus, animals with short breeding seasons should be less responsive to stressors, and therefore less likely to abandon their young. The stress response of each subspecies will be evaluated measuring basal and stress-induced corticosteroid responses to capture and handling, corticosteroid binding globulin levels (to estimate the bioavailability of glucocorticoids), and glucocorticoid receptor levels (to estimate the tissue-specific sensitivity to glucocorticoids).