Mycobionts of many lichen genera appear to demonstrate strong selectivity in the choice of algal partner. The biological properties of a photobiont and its availability in an environment significantly determine the habitat requirements of lichens. Flexibility in photobiont choice extends the ecological amplitude of lichens; therefore, it may constitute an important adaptive strategy for colonization of extreme habitats. The photobiont inventory of the three epigeic lichens most resistant to soil pollution, i.e., Cladonia cariosa, C. rei, and the hyperaccumulator Diploschistes muscorum, was examined to verify whether and to what extent algal composition depends on the type of habitat and substrate enrichment with heavy metals. Photobionts Asterochloris and Trebouxia were identified in the studied lichen species; however, the presence of Trebouxia was directly related to anthropogenic sites with technogenic substrates, and the proportion of lichen specimens with these algae clearly depended on the level of heavy-metal soil pollution and the habitat type. The total number of algal haplotypes increased with increasing soil pollution, and the richness was associated more with soil pollution than with a given lichen species. Additionally, a large number of lichen individuals bearing multiple algal genotypes at polluted sites were recorded. Although Cladonia lichens were previously thought to be restricted to Asterochloris, they are able to start the relichenization process with Trebouxia under specific habitat conditions and to establish a stable association with these algae when colonization of disturbed sites takes place. Comparative analysis of the internal transcribed spacer (ITS) rDNA sequences revealed as many as 13 haplotypes of Trebouxia, and phylogenetic analysis grouped them into two different clades. Such a high level of genetic diversity indicates that Trebouxia is well adapted to metal pollution and could be an alternative photosynthetic partner for certain lichens, especially in polluted sites.

中文翻译：

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后工业栖息地中形成地衣的真菌涉及替代光生物

许多地衣属的分枝菌似乎在选择藻类伙伴时表现出很强的选择性。光生物的生物学特性及其在环境中的可用性显着决定了地衣的栖息地要求。光生物选择的灵活性扩展了地衣的生态范围；因此，它可能构成极端栖息地殖民化的重要适应性策略。对三种最能抵抗土壤污染的表生地衣（即 Cladonia cariosa、C. rei 和超富集植物 Diploschistes muscorum）的光生生物清单进行了检查，以验证藻类成分是否以及在多大程度上取决于栖息地的类型和基质富集重金属。在研究的地衣物种中发现了光生物 Asterochloris 和 Trebouxia；然而，Trebouxia的存在与具有技术底物的人为地点直接相关，地衣标本中含有这些藻类的比例显然取决于重金属土壤污染水平和栖息地类型。藻类单倍型的总数随着土壤污染的增加而增加，并且丰富度与土壤污染的相关性比与给定的地衣物种有关。此外，在污染地点记录了大量携带多种藻类基因型的地衣个体。尽管以前认为 Cladonia 地衣仅限于 Asterochloris，但它们能够在特定栖息地条件下用 Trebouxia 开始重新地衣化过程，并在受到干扰的地点定殖时与这些藻类建立稳定的联系。内部转录间隔 (ITS) rDNA 序列的比较分析揭示了 Trebouxia 的多达 13 个单倍型，系统发育分析将它们分为两个不同的进化枝。如此高水平的遗传多样性表明 Trebouxia 很好地适应了金属污染，并且可能成为某些地衣的替代光合作用伙伴，尤其是在污染地点。