Recent studies have uncovered remarkable diversity in Dictyonema s.lat. basidiolichens, here recognized as subtribe Dictyonemateae. This group includes five genera and 148 species, but hundreds more await description. The photobionts of these lichens belong to Rhizonema, a recently resurrected cyanobacterial genus known by a single species. To further investigate photobiont diversity within Dictyonemateae, we generated 765 new cyanobacterial sequences from 635 specimens collected from 18 countries. The ITS barcoding locus supported the recognition of 200 mycobiont (fungal) species among these samples, but the photobiont diversity was comparatively low. Our analyses revealed three main divisions of Rhizonema, with two repeatedly recovered as monophyletic (proposed as new species), and the third mostly paraphyletic. The paraphyletic lineage corresponds to R. interruptum and partnered with mycobionts from all five genera in Dictyonemateae. There was no evidence of photobiont‐mycobiont co‐speciation, but one of the monophyletic lineages of Rhizonema appears to partner predominantly with one of the two major clades of Cora (mycobiont) with samples collected largely from the northern Andes. Molecular clock estimations indicate the Rhizonema species are much older than the fungal species in the Dictyonemateae, suggesting that these basidiolichens obtained their photobionts from older ascolichen lineages and the photobiont variation in extant lineages of Dictyonemateae is the result of multiple photobiont switches. These results support the hypothesis of lichens representing "fungal farmers," in which diverse mycobiont lineages associate with a substantially lower diversity of photobionts by sharing those photobionts best suited for the lichen symbiosis among multiple and often unrelated mycobiont lineages.

中文翻译：

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在快速辐射的氰基青霉素进化枝中广泛的光生物体共享

最近的研究发现了双歧杆菌的显着多样性。basidiolichens，在这里被称为Dictyonemateae。这一组包括五个属和148个物种，但还有数百个尚待描述。这些地衣的光生生物属于Rhizonema，这是最近复活的蓝细菌属，被一个物种所知。为了进一步研究双扇菌科内光生物子的多样性，我们从18个国家/地区收集的635个标本中产生了765个新的蓝细菌序列。ITS条码基因座支持在这些样品中识别200种真菌生物（真菌）物种，但是光生物体多样性相对较低。我们的分析揭示了根瘤菌的三个主要部分，其中有两个反复被恢复为单系的（提议为新物种），而第三个则大多是共生的。属植物宗谱对应于中断杆菌（R.interruptum），并与扇形纲所有五个属的霉菌伴生。没有证据表明有光生物-真菌共生共形态，但是根瘤菌的单系谱系之一似乎主要与科拉的两个主要进化枝之一（真菌生物）结成伙伴，大部分样品来自安第斯山脉北部。分子钟估计表明根瘤菌该物种比Dictyonemateae中的真菌物种年龄要长得多，这表明这些basidiolichens是从较老的ascolichen谱系获得其光合生物的，而Dictyonemateae现有谱系中的光生物体变异是多种光生物体转换的结果。这些结果支持了代表“真菌农”的地衣的假说，在该假说中，多种真菌生物素谱系通过在多个且通常不相关的真菌生物素谱系之间共享最适合地衣共生的光生物素，而使光生物素的多样性显着降低。