Collaborative Research: Dimensions: Desiccation and Diversity in Dryland Mosses

苔藓是陆地植物种类第二多的类群，在陆地生态系统中起着重要的生态作用。自从大约4.5亿年前与其他陆地植物早期分化以来，苔藓采取了与维管植物不同的途径来解决陆地环境对生存和繁殖造成的挑战。在苔藓中发育良好的一个重要特性是干燥而不死亡的能力，称为干燥耐受性（DT）。这一关键特性使许多苔藓即使在干旱地区也能生存和繁殖，这可能是它们在当前快速气候变化面前生存的关键。合毛藓是一种大型的、种类繁多的藓属，分布在世界各地，通常生长在旱地。尽管它们在某些群落（如生物土壤结皮）中占主导地位，但令人惊讶的是，人们对这一分支中生物多样性的驱动因素知之甚少。这个跨学科的项目整合了基因组、有机体、种群和社区组织水平的研究，以建立对镰状虫过去和现在生物多样性维度的有力理解。总体目标是了解在这些不同层次的组织中产生和维持功能多样性的进化和生态机制，并通过以下方式促进培训、教学和学习：(1)通过实地和实验室研究进行正规教育；(2)非正式教育，包括课堂单元、苔藓和生物外壳从干燥休眠过渡的系列短片、公民科学项目“地壳公民”，以及一系列免费的公共研讨会。该研究将通过研究在不同程度的水分胁迫环境中驱动多样性、繁殖、栖息地选择和生理性状进化的潜在性状（包括表型可塑性）机制，研究无性繁殖和有性繁殖之间、表型可塑性和特化基因型之间的权衡。具体方法包括：(1)对犬链球菌和乡村链球菌进行全基因组测序；(2)利用下一代测序（NGS）开发用于群体水平遗传变异研究的基因型标记，用于表型分析（与生态生理和生态系统调查相关）的签名转录组工具，以及用于系统发育分析的多个单拷贝基因；(3)通过转录组学实验比较两种植物不同发育阶段和性别对干燥胁迫和生殖状态的响应；(3)对caninervis和S. uralis多居群和北美洲合毛虫全部15种进行生态生理实验，以评估DT关键性状的表型可塑性；(5)不同环境下犬链球菌和乡村链球菌的种群遗传研究；(6)建立一个健全的合毛虫系统发育，并利用它来了解所研究性状之间的进化趋势和相关性，并产生一个精细的分类；(7)在田间和温室试验中，研究了基因、功能和系统发育多样性在合毛菌（与共生的苔藓、地衣和蓝藻）主导的生物结壳群落对气候变化的适应能力中的作用。

Mosses are the second most diverse group of land plants and they play important ecological roles in terrestrial ecosystems. Since an early divergence from other land plants some 450 million years ago, mosses took a different path than vascular plants to solving the challenges to survival and reproduction posed by terrestrial environments. One important trait that is well developed in mosses is the capability of drying without dying, known as desiccation tolerance (DT). This critical trait allows many mosses to survive and reproduce even in drylands, and may be the key to their survival in the face of current, rapid climate change. Syntrichia is a large and diverse genus of mosses occurring worldwide and generally in dryland habitats. Despite their dominance in certain communities such as biological soil crusts, surprisingly little is known about the drivers of biodiversity in this clade. This interdisciplinary project integrates research from genomic, organismal, population, and community levels of organization in order to build a robust understanding of past and present dimensions of biodiversity in Syntrichia. The overall goals are to understand the evolutionary and ecological mechanisms that have produced and maintained functional diversity at these different levels of organization, and promote training, teaching, and learning via: (1) formal education through field and laboratory research; (2) informal education involving a classroom module, short-film series featuring mosses and biocrusts transitioning from desiccation dormancy, a citizen science program "Citizens of the Crust," and a series of free public workshops.The research will examine tradeoffs between asexual and sexual reproduction, and between phenotypic plasticity and canalization into specialized genotypes, by examining the mechanisms underlying traits (including phenotypic plasticity) that drive diversification, reproduction, habitat selection, and physiological trait evolution in environments with varying degrees of water stress. Specific methods to be employed include: (1) sequencing the full genomes of S. caninervis and S. ruralis; (2) using next generation sequencing (NGS) to develop genotypic markers for population-level genetic variation studies, signature transcriptome tools for phenotypic analyses (related to ecophysiological and ecosystem investigations), and multiple single-copy genes for phylogenetic analysis; (3) transcriptomics experiments comparing different development stages and sexes of both species in response to desiccation stress and reproductive state; (3) ecophysiological experiments on multiple populations of S. caninervis and S. ruralis, and all 15 species of N. American Syntrichia, to assess phenotypic plasticity in the key trait of DT; (5) population genetic studies of S. caninervis and S. ruralis in different environments; (6) building a robust phylogeny for Syntrichia and using it to understand evolutionary trends and correlations among the traits under study, as well as to produce a refined classification; (7) examining the role of genetic, functional, and phylogenetic diversity in the resilience to climate change of biocrust communities that are dominated by Syntrichia (with co-occurring mosses, lichens, and cyanobacteria) in field and greenhouse experiments.