Lichens are symbiotic associations resulting from interactions among fungi (primary and secondary mycobionts), algae and/or cyanobacteria (primary and secondary photobionts), and specific elements of the bacterial microbiome associated with the lichen thallus. The question of what is a species, both concerning the lichen as a whole and its main fungal component, the primary mycobiont, has faced many challenges throughout history and has reached new dimensions with the advent of molecular phylogenetics and phylogenomics. In this paper, we briefly revise the definition of lichens and the scientific and vernacular naming conventions, concluding that the scientific, Latinized name usually associated with lichens invariably refers to the primary mycobiont, whereas the vernacular name encompasses the entire lichen. Although the same lichen mycobiont may produce different phenotypes when associating with different photobionts or growing in axenic culture, this discrete variation does not warrant the application of different scientific names, but must follow the principle "one fungus = one name". Instead, broadly agreed informal designations should be used for such discrete morphologies, such as chloromorph and cyanomorph for lichens formed by the same mycobiont but with either green algae or cyanobacteria. The taxonomic recognition of species in lichen-forming fungi is not different from other fungi and conceptual and nomenclatural approaches follow the same principles. We identify a number of current challenges and provide recommendations to address these. Species delimitation in lichen-forming fungi should not be tailored to particular species concepts but instead be derived from empirical evidence, applying one or several of the following principles in what we call the LPR approach: lineage (L) coherence vs. divergence (phylogenetic component), phenotype (P) coherence vs. divergence (morphological component), and/or reproductive (R) compatibility vs. isolation (biological component). Species hypotheses can be established based on either L or P, then using either P or L (plus R) to corroborate them. The reliability of species hypotheses depends not only on the nature and number of characters but also on the context: the closer the relationship and/or similarity between species, the higher the number of characters and/or specimens that should be analyzed to provide reliable delimitations. Alpha taxonomy should follow scientific evidence and an evolutionary framework but should also offer alternative practical solutions, as long as these are scientifically defendable. Taxa that are delimited phylogenetically but not readily identifiable in the field, or are genuinely cryptic, should not be rejected due to the inaccessibility of proper tools. Instead, they can be provisionally treated as undifferentiated complexes for purposes that do not require precise determinations. The application of infraspecific (gamma) taxonomy should be restricted to cases where there is a biological rationale, i.e., lineages of a species complex that show limited phylogenetic divergence but no evidence of reproductive isolation. Gamma taxonomy should not be used to denote discrete phenotypical variation or ecotypes not warranting the distinction at species level. We revise the species pair concept in lichen-forming fungi, which recognizes sexually and asexually reproducing morphs with the same underlying phenotype as different species. We conclude that in most cases this concept does not hold, but the actual situation is complex and not necessarily correlated with reproductive strategy. In cases where no molecular data are available or where single or multi-marker approaches do not provide resolution, we recommend maintaining species pairs until molecular or phylogenomic data are available. This recommendation is based on the example of the species pair Usnea aurantiacoatra vs. U. antarctica, which can only be resolved with phylogenomic approaches, such as microsatellites or RADseq. Overall, we consider that species delimitation in lichen-forming fungi has advanced dramatically over the past three decades, resulting in a solid framework, but that empirical evidence is still missing for many taxa. Therefore, while phylogenomic approaches focusing on particular examples will be increasingly employed to resolve difficult species complexes, broad screening using single barcoding markers will aid in placing as many taxa as possible into a molecular matrix. We provide a practical protocol how to assess and formally treat taxonomic novelties. While this paper focuses on lichen fungi, many of the aspects discussed herein apply generally to fungal taxonomy. The new combination Arthonia minor (Lücking) Lücking comb. et stat. nov. (Bas.: Arthonia cyanea f. minor Lücking) is proposed.

地衣是由真菌（初级和次级真菌）、藻类和/或蓝藻（初级和次级光生物）以及与地衣菌体相关的细菌微生物组的特定元素之间相互作用产生的共生关联。什么是物种的问题，无论是关于整个地衣还是它的主要真菌成分，主要的真菌生物，在历史上都面临着许多挑战，并且随着分子系统发育学和系统基因组学的出现达到了新的层面。在本文中，我们简要修改了地衣的定义以及科学和白话命名约定，得出的结论是，通常与地衣相关的科学拉丁化名称总是指原始真菌，而白话名称则涵盖整个地衣。虽然同一个地衣分枝菌在与不同的光生物结合或在无菌培养中生长时可能会产生不同的表型，但这种离散的变异并不保证应用不同的学名，但必须遵循“一种真菌=一个名称”的原则。取而代之的是，对于这种离散形态，应使用广泛同意的非正式名称，例如由相同的真菌生物形成但与绿藻或蓝藻形成的地衣的氯仿和氰基。地衣形成真菌中物种的分类识别与其他真菌没有区别，概念和命名方法遵循相同的原则。我们确定了一些当前的挑战，并提供了解决这些挑战的建议。地衣形成真菌的物种定界不应根据特定物种概念进行调整，而应从经验证据中得出，在我们称为 LPR 方法中应用以下一项或多项原则：谱系 (L) 一致性与发散性（系统发育成分） )、表型 (P) 一致性与发散性（形态成分）和/或生殖 (R) 相容性与隔离性（生物成分）。物种假设可以基于 L 或 P 建立，然后使用 P 或 L（加 R）来证实它们。物种假设的可靠性不仅取决于特征的性质和数量，还取决于上下文：物种之间的关系和/或相似性越密切，应分析的特征和/或标本的数量就越多，以提供可靠的定界. Alpha 分类法应遵循科学证据和进化框架，但也应提供替代的实用解决方案，只要这些在科学上是可辩护的。系统发育上已定界但在该领域不易识别或真正神秘的分类群不应因无法获得适当工具而被拒绝。相反，出于不需要精确确定的目的，它们可以暂时被视为未分化的复合物。种下 (gamma) 分类法的应用应仅限于存在生物学原理的情况，即 系统发育上已定界但在该领域不易识别或真正神秘的分类群不应因无法获得适当工具而被拒绝。相反，出于不需要精确确定的目的，它们可以暂时被视为未分化的复合物。种下 (gamma) 分类法的应用应仅限于存在生物学原理的情况，即 系统发育上已定界但在该领域不易识别或真正神秘的分类群不应因无法获得适当工具而被拒绝。相反，出于不需要精确确定的目的，它们可以暂时被视为未分化的复合物。种下 (gamma) 分类法的应用应仅限于存在生物学原理的情况，即.，显示有限的系统发育差异但没有生殖隔离证据的物种复合体的谱系。伽马分类学不应用于表示不保证在物种水平上进行区分的离散表型变异或生态型。我们修改了形成地衣的真菌中的物种对概念，它识别具有与不同物种相同的潜在表型的有性和无性繁殖形态。我们得出结论，在大多数情况下，这个概念不成立，但实际情况很复杂，不一定与生殖策略相关。如果没有可用的分子数据或单或多标记方法不能提供分辨率，我们建议保持物种对，直到分子或系统发育数据可用。此建议基于物种对的示例Usnea aurantiacoatra vs. U. antarctica，这只能通过系统基因组学方法解决，例如微卫星或 RADseq。总体而言，我们认为地衣形成真菌的物种定界在过去 30 年中取得了显着进展，从而形成了一个坚实的框架，但许多类群仍然缺乏经验证据。因此，虽然关注特定实例的系统基因组学方法将越来越多地用于解决复杂的物种复合体，但使用单一条形码标记进行广泛筛选将有助于将尽可能多的分类群放入分子矩阵中。我们提供了一个实用的协议，如何评估和正式对待分类新奇。虽然本文侧重于地衣真菌，但本文讨论的许多方面普遍适用于真菌分类。新组合Arthonia minor(Lücking) Lücking 梳子。等统计 十一月 (Bas.: Arthonia cyanea f. minor Lücking) 被提议。