EAGER: The impact of selection and temperate-tropical transitions on the evolution of New World bird diversity

已经观察到了生物多样性的许多基本模式，但事实证明，解释这些模式具有挑战性。特别是，热带(赤道以北和以南约23.5°)的物种比温带多得多，这些热带物种中的许多在生理、行为和身体形态上都有显著的差异。其中一些差异被认为是物种数量的进化驱动因素；例如，雌性可以从许多相互竞争的雄性中选择的物种可能更容易分裂成多个物种，因为雌性的偏好可能很快就会改变。检验这一假说和相关假说需要对难以量化的物种特征建立全面的数据库，包括社会群体规模和繁育系统。该项目将产生第一个公开可用的大规模数据集，其中包括衡量女性选择的重要性的指标--男性睾丸的大小。这些数据将为新大陆鸟类的大样本进行汇编，并用于测试纬度、繁殖系统、社会制度和物种形成率之间的关系。了解这些关系是解释大范围多样性模式的基础，这为保护规划和政策提供了信息。该项目测试了一种假说，即温带-热带生物地理转变影响新大陆鸣禽交配和社会制度的进化，最终这些行为特征可能反过来影响多样性比率。具体地说，这项工作将侧重于根据博物馆标本数据汇编所有新大陆鸣禽的组合睾丸质量数据集，并以不偏向于繁殖纬度的方式进行统一分析。由于睾丸大小与精子竞争程度相关，这些数据可以作为繁殖系统的替代指标，以检验热带生境选择遗传一夫一妻制的假设，有利于社会性的进化(特别是合作育种)。新大陆鸣禽是解决这些问题的理想之选，因为它们多种多样，曾多次在热带和温带之间过渡，在博物馆藏品中有很好的代表性，而且几乎所有的鸣禽都已被列入物种水平的系统发育图(鸟类除外，本项目将为其生成第一个系统发育图)。这些数据和分析将构成对新大陆鸟类纬度、物种特征和多样化比率之间关系的更广泛测试的基础。

Many fundamental patterns of biological diversity have been observed, but explaining these patterns has proven challenging. In particular, the tropics (the area ~23.5° north and south of the equator) harbor many more species than the temperate zones, and many of these tropical species are significantly differentiated in their physiology, behavior, and body morphology. Some of these differences have been proposed as evolutionary drivers of species numbers; for instance, species in which females can choose from many competing males may fragment into multiple species more easily as female preferences can quickly change. Testing this and related hypotheses requires comprehensive databases of hard-to-quantify species characteristics, including social group sizes and breeding system. This project will produce the first publicly available large-scale data set that includes a metric of the importance of female choice, male testis size. These data will be compiled for a large sample of New World birds, and used to test for relationships among latitude, breeding system, social system, and the rate of speciation. Understanding these relationships is fundamental to explaining broad-scale diversity patterns, which informs conservation planning and policy.This project tests the hypothesis that temperate-tropical biogeographic transitions affect the evolution of mating and social systems in New World oscine passerine birds, and ultimately that these behavioral characteristics in turn may have affected diversification rates. Specifically, this work will focus on compilation of a data set of combined testis mass for all New World oscines based on museum specimen data, uniformly analyzed in a fashion unbiased with regard to breeding latitude. Due to the correlation of testis size with the degree of sperm competition, these data can be used as a proxy for breeding system, to test the hypothesis that tropical habitats select for genetic monogamy, favoring the evolution of sociality (in particular, cooperative breeding). New World oscines are ideal for addressing these issues as they are diverse, have transitioned between the tropics and temperate zone many times, are well-represented in museum collections, and nearly all have been included in species-level phylogenies (with the exception of wrens, for which this project will generate the first phylogeny). These data and analyses will form the basis for broader tests of the relationship among latitude, species traits, and diversification rates in New World birds.