The morpho-functional evolution of bird beaks and skulls

人们广泛地描述了某些鸟类的喙和头骨是如何被修改和适应的，以不同的和不同的食物为食。达尔文的雀类是一个如此经典的例子，以至于在这种情况下引用它们几乎是老生常谈，但它们相当有效地说明了这一领域目前的研究水平。尽管经过了几十年的详细的生态学研究和最近的发育研究，直到今年早些时候，一项研究才最终开始量化不同形状的雀类头骨和喙如何产生不同的咬合力和对骨折的抵抗力--这些特征决定了这些鸟类能够利用哪些食物和环境。这可能是一个很好的例子，表明我们认为自己对鸟类及其头骨的形态、功能和多样性了解了多少，而这一领域实际上进行了多少定量分析。除了将不同的形状与不同的环境联系起来外，我们对鸟类喙和头骨的形状如何影响它们的功能和觅食生态知之甚少。尽管头骨和喙的形态对鸟类的多样性有很大的贡献，但这一点还是存在的。例如，所有以腐肉或大种子为食的鸟类，是否都有形状相同、功能相同的头骨和喙？它们是否以类似的方式弯曲和施加压力，并产生等量的咬合力？为了以同样的方式发挥作用，它们真的需要相同的大小和形状吗？此外，因为群体中的大多数成员都会飞，鸟类通常被认为是动物中的一个典型例子，因为需要减轻体重(质量)，它们可以采用的不同身体形式的数量受到限制。真的是这样吗？有没有未实现的头骨和喙的形状可以更好地完成这项工作？为什么我们在活着的动物身上看不到这种形状的喙和头骨呢？这项研究旨在解决这些问题，以及这对鸟类肌肉骨骼进化和多样性意味着什么。我们的团队拥有专业知识，可以使用一系列方法来量化头骨的形态和生物力学功能的变化，并将其与我们首创的用于询问假想或祖先形态功能的新工具联系起来。我们拥有相关动物的技术能力、经验和知识，可以定量地确定积极处理食物的选定鸟类群体中头骨和喙形状的变化模式。然后，我们将使用我们在头骨生物力学和工程分析方面的强大背景来确定摄食生物力学中的功能变异，以及具有相似摄食生态的鸟类是否具有相似形状的喙和头骨，并以相同的方式发挥功能。我们预测，如果形式和功能之间存在紧密联系，并且汇聚或并行进化正在发挥作用，情况就会是这样。我们还将测试共享祖先在决定我们所看到的不同形状和功能的范围方面所起的作用。使用我们最近开发的软件工具，我们将发现假想的或祖先的头骨和喙形状在抵抗摄食负荷方面比我们现有的鸟类群体拥有的形状更好。最后，我们将确定喙形状的变化在多大程度上取决于脑壳形状的变化，以及喙和脑壳形状之间的松散关系是否可以帮助鸟类形成更多样化的头骨形态。来自不同学科的研究人员将从这项工作中受益--比较解剖学家、生物机械学家、进化和发育生物学家、古生物学家和生物医学工程师。通过对年轻科学家的多学科培训和欧盟海外合作，英国的科学基地将受益。这部作品的视觉方面，以及对鸟类的关注，可能会吸引普通公众，提供公众参与机会和媒体兴趣。

It is widely described how certain bird beaks and skulls are modified and adapted for feeding on distinct and different foodstuffs. Darwin's finches are such a classic example that to cite them in this context is almost a cliché, yet they illustrate the current level of research in this area quite effectively. Despite decades of detailed ecological and more recently developmental studies, it was only earlier this year that a study finally began to quantify how different shaped finch skulls and beaks generated different bite forces and resistance to fracture - features which dictate which foodstuffs and environments these birds are capable of exploiting. This is probably a good example of how much we think we know about form, function and diversity of birds and their skulls, compared to how much quantitative analysis has actually been performed in this area. We do not know a huge deal about how the shapes of bird beaks and skulls influence their function and feeding ecology, beyond just linking different shapes to different environments. This is despite the fact that cranial and beak morphology contributes to a significant amount of avian diversity. For example, do all birds that feed on carrion, or large seeds, have skulls and beaks that are shaped the same, and function in the same way? Do they bend and stress in a similar manner, and generate equivalent amounts of bite force? And to function in the same manner, do they indeed need to be the same size and shape? Furthermore, because most members of the group can fly, birds are often assumed to be a classic example of animals that are constrained in the number of different body forms they can adopt by the need to reduce weight (mass). Is this indeed the case? Are there unrealised shapes of skulls and beaks that could do the job better? And why do we not see beaks and skulls shaped in this manner in living animals? This study sets out to address these questions, and what this means for musculoskeletal evolution and diversity in birds. Our team has the expertise to employ a range of methodologies to quantify variation in form and biomechanical function in skulls, and link this to new tools that we have pioneered to interrogate the function of hypothetical or ancestral morphologies. Between us we have the technical ability, experience and knowledge of the animals concerned to quantitatively determine the patterns of skull and beak shape variation in selected groups of birds that actively process their food. We will then use our strong background in biomechanical and engineering analysis of skulls to determine functional variation in feeding biomechanics, and whether birds that share similar feeding ecologies are have similar shaped beaks and skulls, and function in the same manner. We would predict this to be the case if there were a tight link between form and function and convergent or parallel evolution were at play. We will also test what role shared ancestry plays in determining the range of different shapes and functions we see. Using our recently developed software tools we will find out if hypothetical or ancestral skull and beak shapes were better at resisting feeding loads than those possessed by our living bird groups. Finally, we will determine to what extent changes in the shape of the beak are contingent on changes to the shape of the braincase, and whether a loose relationship between beak and braincase shape can help birds develop more diverse skull morphologies. Researchers from a variety of disciplines will benefit from this work - comparative anatomists, biomechanists, evolutionary and developmental biologists, palaeontologists, and biomedical engineers. There will be benefits to the UK science base through multidiscplinary training of young scientists and overseas EU collaboration. The visual aspect of this work, and the focus on birds, is likely to appeal to the general public, offering public engagement opportunities and media interest.