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，它塑造了生物体在生命后期的物理和内部表达。 它可以影响大小，形状和内部质量，如免疫系统的强度和神经/大脑系统的质量。 胚胎发育的速度在物种之间有很大的差异，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生物慢得多，这在鸣禽中非常明显。 经典的解释是，较慢的发育是有利的，因为它允许增强特化细胞的发育，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。 本研究将沿着探讨鸟类孵化期纬向变化的3个替代性假设：1）经典的后代质量假设，2）外部成年死亡率，3）食物限制，4）巢捕食。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，并与亚利桑那州长期进行的研究中的相关物种进行比较。 这项工作将使用食物和其他假设因素的实验操作来测试替代品，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。这项工作有可能扭转长期以来对发育缓慢的原因和后果的看法。 与此同时，它将提供新的见解，生态因素有利于变化的发展速度，以及利益和成本的变化，后代的质量。 拟议的工作将提供大量的本科生，研究生和博士后研究人员的不同美国和国际（拉丁美洲）社区的整合和培训的广泛机会。简而言之，拟议的工作将提供一个独特的跨文化生活经验，以及严格的教育和实地经验，每年许多本科生。

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.