The current classification system for the recognition of taxonomic ranks among fungi, especially at high-ranking level, is subjective. With the development of molecular approaches and the availability of fossil calibration data, the use of divergence times as a universally standardized criterion for ranking taxa has now become possible. We can therefore date the origin of Ascomycota lineages by using molecular clock methods and establish the divergence times for the orders and families of Dothideomycetes. We chose Dothideomycetes, the largest class of the phylum Ascomycota, which contains 32 orders, to establish ages at which points orders have split; and Pleosporales, the largest order of Dothideomycetes with 55 families, to establish family divergence times. We have assembled a multi-gene data set (LSU, SSU, TEF1 and RPB2) from 391 taxa representing most family groups of Dothideomycetes and utilized fossil calibration points solely from within the ascomycetes and a Bayesian approach to establish divergence times of Dothideomycetes lineages. Two separated datasets were analysed: (i) 272 taxa representing 32 orders of Dothideomycetes were included for the order level analysis, and (ii) 191 taxa representing 55 families of Pleosporales were included for the family level analysis. Our results indicate that divergence times (crown age) for most orders (20 out of 32, or 63%) are between 100 and 220 Mya, while divergence times for most families (39 out of 55, or 71%) are between 20 and 100 Mya. We believe that divergence times can provide additional evidence to support establishment of higher level taxa, such as families, orders and classes. Taking advantage of this added approach, we can strive towards establishing a standardized taxonomic system both within and outside Fungi. In this study we found that molecular dating coupled with phylogenetic inferences provides no support for the taxonomic status of two currently recognized orders, namely Bezerromycetales and Wiesneriomycetales and these are treated as synonyms of Tubeufiales while Asterotexiales is treated as a synonym of Asterinales. In addition, we provide an updated phylogenetic assessment of Dothideomycetes previously published as the Families of Dothideomycetes in 2013 with a further ten orders and 35 families.

中文翻译：

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使用发散时间对较高的分类单元进行排名：以多菌藻为例

当前用于识别真菌中的生物分类等级的分类系统是主观的，尤其是在高等级的分类系统中。随着分子方法的发展和化石校准数据的可用性，使用发散时间作为对分类单元进行排名的通用标准已成为可能。因此，我们可以使用分子钟方法来确定子囊菌谱系的起源，并确定十二指肠菌纲和科的发散时间。我们选择了十二生孢子纲（Acomycota门）中最大的一类，该纲目包含32个纲目，以确定各纲目分裂的年龄。和胸骨，是拥有55个家庭的最大的Dothideomycetes订单，以建立家庭分歧时间。我们从391个分类单元中收集了多基因数据集（LSU，SSU，TEF1和RPB2），这些分类单元代表了多菌丝菌的大多数家族，并仅利用子囊菌内部的化石校准点和贝叶斯方法来确定多菌丝菌谱系的发散时间。分析了两个分离的数据集：（i）包括代表32个丝状菌的订单的272个分类单元，以进行订单水平分析；以及（ii）代表了55个of骨科的191个分类单元。包括在家庭水平分析中。我们的结果表明，大多数订单（32个中的20个，即63％）的发散时间（王冠年龄）在100至220 Mya之间，而大多数家庭（55个中的39个，即71％）的发散时间在20至80 Mya之间。 100妙。我们认为，分歧时间可以提供更多证据来支持建立更高级别的分类单元，例如家庭，订单和阶级。利用这种添加的方法，我们可以努力在真菌内部和外部建立标准化的分类系统。在这项研究中，我们发现分子定年与系统发育推论对目前两个公认的目（Bezerromycetales和Wiesneriomycetales）的分类状态不提供任何支持。和这些被视为同义词Tubeufiales而Asterotexiales被作为同义词处理Asterinales。此外，我们提供了以前作为2013年出版的Dothideomycetes家族的Dothideomycetes的最新系统发育评估，另外还有10个订单和35个科。