The Gene and Gene Expression (GAGE) species concept, a new version of the Pragmatic Species Concept of Seifert (2014), is proposed as a concept applicable to any described recent or fossil eukaryotic organism independent from its mode of reproduction or evolutionary history. In addition to presenting the concept as such, the paper also provides practical recommendations for taxonomists when delimiting species and describing taxa. The wording of the new concept contains a heading core sentence plus five attached sentences addressing essential conditions for its translation into a sound taxonomic practice: "Species are separable clusters that have passed a threshold of evolutionary divergence and are exclusively defined by nuclear DNA sequences and/or their expression products. Nuclear DNA sequences and their expression products are different character systems but have a highly correlated indicative function. Character systems with the least risk of epigenetic or ontogenetic modification have superior indicative value when conflicts between character systems of integrative studies arise. All character systems have to be described by an adequate numerics allowing cluster formation and determination of thresholds. Thresholds for each character system should be fixed by consensus among the experts under the principle of avoiding oversplitting or lumping. Clusters must not be the expression of intraspecific polymorphism." Recognizing the distortions and conflicts caused to taxonomy through barcoding or through assessment on the basis of association with other organisms, the GAGE species concept strongly downgrades the use of cytoplasmic DNA of endosymbiotic origin (mtDNA, cpDNA) or DNA of closely associated microbes (e.g. Wolbachia bacteria) for final taxonomic decision making. Recognizing the distortion of phylogenies by the high frequency of reticulate evolution, it is argued that delimiting and naming species has to be separated from constructing bifurcating phylogenetic trees.

中文翻译：

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基因和基因表达 (GAGE) 物种概念：适用于所有真核生物的通用方法

基因和基因表达 (GAGE) 物种概念是 Seifert (2014) 实用物种概念的新版本，被提议作为适用于任何描述的新近或化石真核生物的概念，独立于其繁殖模式或进化历史。除了提出这样的概念外，本文还为分类学家在划定物种和描述分类群时提供了实用的建议。新概念的措辞包含一个标题核心句子和五个附加句子，说明将其转化为健全的分类学实践的基本条件：“物种是可分离的集群，已经通过了进化分歧的阈值，并且完全由核 DNA 序列和/或它们的表达产物。核DNA序列及其表达产物是不同的特征系统，但具有高度相关的指示功能。当综合研究的特征系统之间出现冲突时，表观遗传或个体遗传修饰风险最小的特征系统具有更高的指示价值。所有字符系统都必须用足够的数字来描述，从而允许集群形成和阈值的确定。每个字符系统的阈值应在避免过度分裂或集中的原则下由专家协商确定。集群不能是种内多态性的表达。”认识到通过条形码或通过与其他生物关联的评估对分类学造成的扭曲和冲突，GAGE 物种概念强烈降低了使用内共生来源的细胞质 DNA（mtDNA、cpDNA）或密切相关的微生物（例如 Wolbachia 细菌）的 DNA 进行最终分类决策的程度。认识到高频率的网状进化对系统发育的扭曲，有人认为必须将物种的定界和命名与构建分叉的系统发育树分开。