Collaborative Research: Developmental and functional mechanisms of complex trait re-evolution: Limb loss and gain in skink lizards

理解复杂性状是如何进化的，对于发展性状进化的基本理论至关重要。有这样的理论吗，Dollo？一个多世纪以来，复杂的性状一旦丢失就无法重新进化，这一定律一直困扰着生物学家。尽管最近的证据表明，复杂的性格可以而且确实会重新进化，但人们对这些进化逆转是如何以及为什么发生的缺乏理解。本研究将通过阐明复杂性状再进化的功能基础和发育机制来解决这些问题。该项目将导致功能形态学和发育遗传学在进化框架中的前所未有的整合，促进这些领域之间的交流。该研究项目将采用综合的方法，在系统发育框架中综合发育遗传学和功能形态学，研究东南亚穴居蜥蜴属Brachymeles的肢体和手指丧失及其随后的再进化。本研究的目的是确定丢失的表型性状是否具有相同或不同的功能能力，以及重新进化的手指是否通过与祖先手指相同或不同的发育机制发展。地面运动速度、加速度、挖洞速度和力将使用高速视频和力传感器对祖先和重新进化的五足动物、中间动物和无肢动物进行量化。本文将对短肢动物肢体和趾的缩小和再进化的发育基础进行表征，以确定对肢体和趾再进化的假设发育限制。胚胎中手指间充质凝聚将通过组织化学和原位杂交鉴定与肢体和手指模式相关的9个基因。该项目还将涉及和培训本科生和研究生的研究方法，并将促进国际合作。将积极招募和鼓励少数民族和女学生参加项目提供的研究培训机会。该项目产生的生物主题外展项目将针对弱势社区和当地K-12学校。拟议项目的研究结果将作为已建立的生物多样性信息网站（http://philbreo.lifedesks.org/）的一部分在网上、在科学会议上、在同行评议的期刊上以及通过其他现有数据库（http://datadryad.org/）公开传播。

Understanding how complex characters evolve is central to developing fundamental theories of trait evolution. One such theory, Dollo?s Law, which states that once lost, complex characters cannot be re-evolved, has challenged biologists for more than a century. Despite recent evidence suggesting that complex characters can and do re-evolve, there is a lack of understanding of how and why these evolutionary reversals take place. The proposed study will address these questions by elucidating the functional underpinnings and the developmental mechanisms of complex trait re-evolution. This project will result in an unprecedented integration of functional morphology and developmental genetics in an evolutionary framework, facilitating communication between these fields.The research project will use an integrative approach that synthesizes developmental genetics and functional morphology in a phylogenetic framework to study limb and digit loss and subsequent re-evolution in the Southeast Asian burrowing lizard genus Brachymeles. Objectives of the proposed research are to determine whether a phenotypic trait that has been lost re-evolves with the same or different functional capacities, and whether re-evolved digits develop via the same or different developmental mechanisms as ancestral digits. Surface locomotor velocity, acceleration, and burrowing speed and force will be quantified using high-speed video and a force transducer for ancestrally and re-evolved pentadactyl, intermediate, and limbless species. The developmental basis of limb and digit reduction and re-evolution in Brachymeles will be characterized to identify hypothesized developmental constraints on limb and digit re-evolution. Mesenchymal condensations of digits in embryos will be identified using histochemistry and in situ hybridization of nine genes associated with limb and digit patterning. The project will be also involve and train undergraduate and graduate students in research methods and will promote international collaborations. Minority and female students will be actively recruited and encouraged to participate in the research training opportunities provided by the project. Biologically themed outreach programs resulting from this project will target disadvantaged communities and local K-12 schools. Findings from the proposed project will be publicly disseminated online as part of an established biodiversity information website (http://philbreo.lifedesks.org/), at scientific conferences, in peer-reviewed journals, and through other existing databases (http://datadryad.org/).