Collaborative Proposal: Developmental and Genetic Pathways to Phenotypic Convergence in a Radiation of Groundwater Salamanders

像昆虫和火蜥蜴这样互不相关的洞穴生物通常都有共同的特征--比如没有眼睛，脸色苍白，四肢伸长。地下生活带来了与地表生活不同的挑战，而这些挑战有利于种群水平上相对快速的外表变化(以及其他更微妙的特征)。这些快速的变化导致许多洞穴生物的外观趋同，但导致不同生物重复变化的遗传和发育过程在很大程度上是未知的。得克萨斯州中部的爱德华兹高原有一个广泛的、尽管支离破碎的泉水、洞穴和含水层网络，其中居住着无数不同的地下火蜥蜴。这些火蜥蜴达到生殖成熟的同时，保留了未成熟火蜥蜴特有的特征(如鳃)，其中许多显示出眼睛不同程度地缩小和发育，以及与生活在地下有关的其他特征(如嗅觉增强)。这些特征在不同物种中独立和重复地进化，这项研究将整合通过各种方法获得的信息，以阐明使新结构和功能得以进化的机制。这个项目是及时的，因为除了加强对感官系统进化的了解外，它还将突出和澄清德克萨斯州中部火蜥蜴的多样性，而此时人类人口增长和商业发展进一步威胁到已被确定为濒临灭绝的物种。最后，这个项目将作为一个平台，培训众多的本科生进行STEM研究。研究人员将使用综合的、分层次的方法，结合遗传、发育和系统发育的观点来研究驱动地下地下水火蜥蜴表型趋同的机制。来自微型计算机断层成像、组织学、转录学和外显子测序的结果将显示跨越地下谱系的感觉系统(视觉、嗅觉和侧线)的形态融合程度。比较转录组学将被用来在感觉系统基因的蛋白质编码水平上研究器官系统减少的发育遗传学机制和分子趋同的特征。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。

Cave organisms as unrelated as insects and salamanders often have shared features – such as lack of eyes, pallid coloration, and elongated limbs. Life underground provides different challenges from life on the surface, and those challenges favor relatively rapid changes in appearance (and other, more subtle characteristics) at the population level. Those rapid changes lead to convergence in the appearance of many cave organisms, but the genetic and developmental processes that lead to repeated changes in different organisms are largely unknown. The Edwards Plateau of central Texas has an extensive, though fragmented, network of springs, caves, and aquifers that host numerous, diverse, underground salamanders. These salamanders attain reproductive maturity while retaining features (such as gills) that are characteristic of immature salamanders, and many of them show eyes reduced in size and development to varying degrees, along with other characteristics associated with living underground (e.g. an enhanced sense of smell). These characteristics have evolved independently and repeatedly in the various species, and this research will integrate information derived through a variety of approaches to shed light on the mechanisms that enable new structures and functions to evolve. This project is timely because in addition to enhancing understanding of the evolution of sensory systems, it will highlight and clarify the diversity of salamanders in central Texas at a time when human population growth and commercial development further threaten species that have been identified as being in danger of extinction. Finally, this project will serve as a platform to train numerous undergraduates in STEM research.The researchers will use an integrative, hierarchical approach combining genetic, developmental, and phylogenetic perspectives to study the mechanisms that drive convergence in phenotypes of subterranean Groundwater Salamanders. Results from micro-computed tomography imaging, histology, transcriptomics, and exon sequencing will demonstrate the degree of morphological convergence in sensory systems (visual, olfactory, and lateral line) across subterranean lineages. Comparative transcriptomics will be employed to examine the developmental genetic mechanisms of organ system reduction and signatures of molecular convergence at the protein-coding level in sensory-system genes.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.