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

像昆虫和蝾螈这样不相关的洞穴生物通常有共同的特征--比如没有眼睛，颜色苍白，四肢细长。地下生活提供了与地表生活不同的挑战，这些挑战有利于人口水平上外观（和其他更微妙的特征）的相对快速变化。这些快速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基本上是未知的。德克萨斯州中部的爱德华兹高原有一个广泛的，虽然支离破碎，泉水，洞穴和含水层的网络，容纳了许多不同的地下蝾螈。这些蝾螈达到生殖成熟，同时保留了未成熟蝾螈的特征（如鳃），其中许多蝾螈的眼睛在大小和发育方面都有不同程度的缩小，沿着其他与地下生活有关的特征（如增强的嗅觉）。 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进化的机制。这个项目是及时的，因为除了增强对感觉系统进化的理解，它将突出和澄清在人口增长和商业发展进一步威胁物种已被确定为濒临灭绝的时候，在得克萨斯州中部蝾螈的多样性。最后，该项目将作为培养众多STEM研究本科生的平台。研究人员将使用综合的、分层的方法，结合遗传、发育和系统发育的观点，研究驱动地下水蝾螈表型趋同的机制。来自微计算机断层扫描成像、组织学、转录组学和外显子测序的结果将证明感觉系统（视觉、嗅觉和侧线）在地下谱系中的形态学会聚程度。比较转录组学将用于研究器官系统减少的发育遗传机制和感觉系统基因中蛋白质编码水平的分子趋同特征。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

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.