ARTS: Taxonomy and Molecular Systematics of Mesh Web Spiders (Araneae: Dictynidae)

蜘蛛是一种非常多样化的生物，在世界各地的生态系统中起着至关重要的作用。尽管它们声名狼藉，而且经常引起人们的恐惧，但我们对某些蜘蛛群的了解仍然存在巨大的空白。蜘蛛科的许多蜘蛛通常体型小，呈棕色或灰色，色彩丰富，最引人注目的可能是它们有趣的分布模式和迷人的生态特征。事实上，这个蜘蛛生命树的“黑暗角落”包含了一个群体，几乎占据了地球上每一个陆地生态系统，并且包含了唯一一个完全水生的蜘蛛物种。虽然有些物种只在很小的地区特有，但其他物种是所有蜘蛛物种中分布最广的。单个蜘蛛家族的这种变异水平显示出相当大的潜力，作为一个系统，它可以回答广泛的进化和生态问题，特别是当它们与特定特征或行为的进化有关时。该项目旨在解决这组蜘蛛之间的进化关系及其在蜘蛛生命树中的相对位置，照亮蜘蛛生命树中最鲜为人知的部分之一。此外，该项目的一个主要目标是在美国培养下一代分类学专家、生物生物学家和系统学家。Dictynidae是一个非常多样化的家庭，巢在“marronoid分支”中。因为蜘蛛属之间的关系，属中物种之间的关系，以及蜘蛛生命树中家族之间的关系，在很大程度上是未知的，所以在进化背景下提出有趣问题的努力受到了阻碍。我们的目标是通过创建一个分类学和系统发育的支架来支持未来几年的进一步研究，为该群体的进化和生态研究打开大门。我们将通过：1)利用形态学数据和从下一代测序（NGS）收集的数据来修正中等多样性，罕见的Lathys属；2)利用NGS数据确定所有双翅目属的系统发育关系；3)利用NGS数据确定Dictynidae在蜘蛛生命树中的位置。我们将与我们的多国合作者团队一起收集全球所有大鼠属的标本和代表。所有标本（包括类型）的标准化图像将使用近50个琥珀化石的高分辨率堆叠图像，SEM显微照片和微ct扫描来生成，以允许一致的形态分析。低覆盖率基因组测序将用于产生分子数据，这些数据将与形态学矩阵结合，随后使用贝叶斯推理进行分析。这种方法允许对结合形态学和分子数据集进行分析，这对于包含化石分类群至关重要，随后允许我们使用尖端年代测定来产生时间校准的系统发育。我们将分别在三个分类尺度上进行这些分析：Lathys，所有dictynid属和“marronoid枝”。我们将使用概率推断得出的Lathys系统发育来检验Laurasian生物地理学假说。最后，将进行祖先状态重建，以研究形态特征以及生态和行为特征的演变，包括水生栖息地关联和狩猎策略。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Spiders are an incredibly diverse group of organisms that play an essential role in ecosystems all over the world. In spite of their notoriety and the fear that they often inspire, huge gaps in our knowledge remain for some groups of spiders. Often generalized as small and brown or grey, many spiders in the family Dictynidae are quite colorful, and are perhaps most notable for their intriguing distributional patterns and fascinating ecological characteristics. In fact, this “dark corner” of the spider tree of life comprises a group that occupies virtually every terrestrial ecosystem on earth and contains the only fully aquatic spider species. While some species are endemic to very small areas, others are some of the most widespread of all spider species. This level of variation within a single family of spiders shows considerable potential as a system for answering a broad range of evolutionary and ecological questions, especially as they relate to the evolution of specific characteristics or behaviors. This project aims to resolve the evolutionary relationships among this group of spiders and their relative position within the spider tree of life, shining a light on one of the most poorly known parts of the spider tree of life. Additionally, a main goal of this project is to train the next generation of taxonomic experts, organismal biologists and systematists in Dictynid spiders in the US. Dictynidae are a hugely diverse family nested within the “marronoid clade”. Because the relationships of the genera, of species in the genera, and the relationship of the family within the spider tree of life, are largely unknown, efforts to ask interesting questions in an evolutionary context are stymied. We aim to open the door to evolutionary and ecological studies of the group by creating a taxonomic and phylogenetic scaffold in support of further research for years to come. We will accomplish this by: 1) Revising the moderately diverse, unusual genus Lathys using morphological data and data gathered from Next Generation Sequencing (NGS); 2) Determining the phylogenetic relationships of all dictynid genera using NGS data; 3) Using NGS data to determine the placement of Dictynidae within the spider tree of life. We will collect both specimens of Lathys and representatives of all dictynid genera worldwide with our multinational team of collaborators. Standardized images from all specimens, including types, will be produced using high-resolution stacked images, SEM micrographs, and microCT scanning of nearly 50 amber fossils to allow for consistent morphological analysis. Low coverage genome sequencing will be used to produce molecular data that will be incorporated with the morphological matrix to subsequently be analyzed using Bayesian Inference. This method allows the analysis of a combined morphological and molecular dataset, paramount for the inclusion of fossil taxa, which subsequently allows us to use tip dating to produce a time-calibrated phylogeny. We will conduct these analyses separately at three taxonomic scales: Lathys, all dictynid genera, and the “marronoid clade”. We will use probabilistic inference on the resulting Lathys phylogeny to test Laurasian biogeographic hypotheses. Finally, ancestral state reconstruction will be conducted to examine the evolution of morphological characters as well as ecological and behavioral characters, including aquatic habitat association and hunting strategy.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.