Dimensions: Convergent Evolution of Nectarivory and its Association with High-Altitude Adaptation in Hummingbirds and Sunbirds

研究生物多样性产生机制的一个强有力的方法是关注趋同进化的实例。当同一性状独立进化两次或更多次，提供适应性进化的自然复制时，收敛进化就会发生。例如，在北美和南美洲的蜂鸟中，以及在非洲、亚洲和澳大拉西亚的太阳鸟、猎蜘蛛和啄花鸟身上，以花蜜为食的食物及其伴随的形态适应(例如，具有特殊舌状结构的长锥形喙)已经独立进化。该项目将对这两组鸟类进行研究，以更好地了解导致相关基因和生理进化趋同的生态和遗传因素。这项研究将探索在品尝糖分、代谢酒精以及生活在氧气较少的高海拔地区的能力方面的趋同进化。它还将研究生活在鸟类肠道中的微生物群落的收敛。这项研究将揭示相同的基因变化导致功能相似的生理特征进化的频率，并将导致对适应和物种多样性的更好理解。这项研究将产生蜂鸟、太阳鸟、猎蜘蛛和啄花鸟的综合进化树，这将是保护这些不同鸟类群体的重要资源，这些鸟类群体总共占鸟类物种多样性的5%。该项目将培训三名研究生和一名博士后研究员，学习整合生物信息学、功能生理学、行为生态学、遗传学和系统发育学的研究技术。它还将在尖端的分子遗传技术和生理研究方面培训多达10名本科生，这将为他们提供宝贵的研究经验。这笔赠款将通过与运营“理解进化”网站的教育工作者合作，促进公众对科学的理解，他们将帮助教师开发课程材料，解释蜂鸟和太阳鸟多样化背景下的适应和收敛进化等进化概念。这个项目将研究提高耐缺氧能力的性状的趋同，与蜜腺相关的性状的趋同，并将研究与蜜腺相关的性状如何在高海拔环境中汇聚，这些特征是蜂鸟和太阳鸟多样化的特征。在基因水平上，研究小组将研究与蜜腺相关的基因(即糖味受体、酒精代谢基因)和能够赋予耐低氧能力的基因途径(即血红蛋白、氧磷酸盐和低氧诱导因子途径)。此外，研究人员将对食蜜鸟肠道样本中的16S核糖体RNA基因进行测序，以研究微生物群落。在功能层面上，研究小组将测试基因变化如何改变对生物功能和随后进入新的生态环境的多样性都很重要的表型。为了实现这一目标，该团队将进行生理测试，以测量耐缺氧能力，量化羽毛样本中的饮食酒精暴露(以发酵花蜜的形式)，根据16S rRNA序列预测肠道微生物的代谢功能，在实验室分析不同遗传变体之间的功能差异(例如，测量不同味觉受体变体的响应性的细胞培养试验)，并进行味觉辨别能力的行为测试。在系统发育水平上，研究小组将研究基因和表型的进化史，以揭示两次禽类辐射内部和之间的趋同进化实例。最后，该团队将整合所有的遗传、功能和系统发育数据，以评估：(1)趋同基因进化的流行率如何随时间变化，以及(2)一系列特征如何随着高海拔环境而共同进化。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

A powerful way to study mechanisms that generate biodiversity is to focus on instances of convergent evolution. Convergent evolution occurs when the same trait evolves independently two or more times, providing natural replicates of adaptive evolution. For example, feeding on nectar and its accompanying morphological adaptations (e.g., long tapered bills with specialized tongue structures) have evolved independently in hummingbirds in North and South America, and in the sunbirds, spiderhunters, and flowerpeckers of Africa, Asia, and Australasia. This project will study these two groups of birds to better understand the ecological and genetic factors that lead to convergent evolution in associated genes and physiology. The research will investigate convergent evolution in the ability to taste sugar, metabolize alcohol, and live at high altitudes where there is less oxygen. It will also study convergence in the microbial communities living in the guts of the birds. This study will reveal how often the same genetic changes are responsible for the evolution of functionally similar physiological traits, and will lead to an improved understanding of adaptation and species diversification. The research will result in comprehensive evolutionary trees for hummingbirds, sunbirds, spiderhunters, and flowerpeckers, which will be an important resource for the conservation of these diverse avian groups that together constitute ~5% of bird species diversity. This project will train three graduate students and a postdoctoral fellow in research techniques integrating bioinformatics, functional physiology, behavioral ecology, genetics, and phylogenetics. It will also train up to ten undergraduates in sophisticated molecular genetic techniques and physiological research, which will give them valuable research experience. This grant will promote public understanding of science through a collaboration with educators who run the "Understanding Evolution" website, who will help to develop course materials for teachers that explain evolutionary concepts like adaptation and convergent evolution in the context of the diversification of hummingbirds and sunbirds.This project will study convergence in traits that improve hypoxia resistance, convergence in traits related to nectarivory, and will investigate how traits related to nectarivory may converge in high-altitude environments that characterize the diversification of hummingbirds and sunbirds. On the genetic level, the research team will study genes related to nectarivory (i.e., sugar taste receptors, alcohol metabolism genes) and gene pathways that can confer hypoxia resistance (i.e., hemoglobin, OXPHOS, and hypoxia-inducible factor pathways). In addition, the researchers will sequence 16S ribosomal RNA genes from gut samples of nectarivorous birds to study microbial communities. On the functional level, the research team will test how genetic changes have altered phenotypes important for both organismal function and subsequent diversification into new ecological niches. To accomplish this, the team will perform physiological tests to measure hypoxia resistance, quantify dietary alcohol exposure (in the form of fermented nectar) from feather samples, predict metabolic functions of gut microbes from their 16S rRNA sequences, assay functional differences among genetic variants in the lab (e.g., cell-culture assays that measure responsiveness of different taste receptor variants), and conduct behavioral tests of taste discrimination abilities. On the phylogenetic level, the research team will study the evolutionary history of genes and phenotypes to reveal instances of convergent evolution within and between the two avian radiations. Finally, the team will integrate all genetic, functional, and phylogenetic data to evaluate: (1) how the prevalence of convergent genetic evolution changes with time, and (2) how suites of traits co-evolve in response to high-altitude environments.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.