Life History and Developmental Variation of Tropical Versus Temperate Passerines

胚胎发育是生物体生命中的一个关键阶段，它塑造了有机体在以后生命中的物理和内部表达。它可以影响大小、形状和内在质量，如免疫系统的强度和神经/大脑系统的质量。不同物种的胚胎发育速度差异很大，热带和北温带生物之间的差异尤其明显；热带生物的发育速度比北美的生物慢得多，这一点在鸣禽中非常明显。经典的解释是，较慢的发育速度是有利的，因为它允许促进特定细胞的发育，如免疫系统，以产生更高质量的后代。然而，初步数据对这一长期观点提出了质疑。这一假说将与关于孵化期鸟类纬度变化的3个替代假说一起探讨：1)经典的后代质量权衡假说，2)外在成虫死亡率，3)食物限制，4)巢被捕食。拟议的工作将通过对委内瑞拉安第斯山脉鸟类的持续研究来检验这些假设，并与亚利桑那州正在进行的一项长期研究中的相关物种进行比较。这项拟议的工作将使用对食物和其他假设因素的实验操作来测试这些替代品，同时还将根据孵化时的大小和免疫功能的测量来检查后代的质量。拟议的工作可能会扭转长期以来对发育缓慢的原因和后果的看法。同时，它将为有利于发育速度变异的生态因素以及这种变异对后代质量的好处和代价提供新的见解。拟议的工作将为整合和培训来自美国和国际(拉丁美洲)不同社区的大量本科生、研究生和博士后研究人员提供广泛的机会。简而言之，拟议的工作将为每年许多本科生提供独特的跨文化生活体验以及严格的教育和实地体验。

Embryonic development is a critical stage in the life of organisms that shapes the physical and internal expression of the organism later in life. It can influence size, shape, and internal quality such as the strength of the immune system and quality of the neural/brain system. Rate of embryonic development varies dramatically among species, with an especially strong difference between tropical and north temperate organisms; tropical organisms develop much slower than organisms in North America, and this is very clear in songbirds. The classic explanation is that slower development is favored because it allows enhanced development of specialized cells, such as the immune system, to yield higher quality offspring. Yet, preliminary data raise questions about this long-standing view. This hypothesis will be explored along with 3 alternative hypotheses for the latitudinal variation in incubation periods of birds: 1) the classic trade-off with offspring quality hypothesis, 2) extrinsic adult mortality, 3) food limitation, and 4) nest predation. Proposed work will examine these hypotheses through continued studies of birds in the Andes of Venezuela to compare with related species in a long-term ongoing study in Arizona. The proposed work will use experimental manipulation of food and other hypothesized factors to test the alternatives, while also examining offspring quality based on size at hatching and measures of immune function.The proposed work has the potential to reverse long-standing views of the causes and consequences of slow development. At the same time, it will provide new insight into ecological factors favoring variation in the rate of development as well as the benefits and costs of that variation to quality of offspring. The proposed work will provide extensive opportunities for the integration and training of large numbers of undergraduate, graduate, and post-doctoral researchers of diverse U.S. and international (Latin American) communities. In short, the proposed work will provide a unique cross-cultural life experience as well as stringent educational and field experience for many undergraduates each year.