Data from: Fungal specificity and selectivity for algae play a major role in determining lichen partnerships across diverse ecogeographic regions in the lichen-forming family Parmeliaceae

Microbial symbionts are instrumental to the ecological and long-term evolutionary success of their hosts, and the central role of symbiotic interactions is increasingly recognized across the vast majority of life. Lichens provide an iconic model for investigating patterns in species interactions, although relationships among lichen symbionts are often masked by uncertain species boundaries or inability to reliably identify symbionts. The species-rich lichen-forming fungal family Parmeliaceae provides a valuable system for assessing patterns of interactions of algal symbionts at various scales, and our study addresses patterns of lichen symbiont interactions at the largest geographical and taxonomical scales ever attempted. We analyzed a total of 2356 algal ITS sequences collected from lichens representing ten mycobiont genera in Parmeliaceae, two genera in Lecanoraceae, and 20 cultured Trebouxia strains. Algal sequences were grouped into operational taxonomic units (OTUs), and we explored patterns of symbiont interactions in these lichens based on ecogeographic distributions and mycobiont taxonomy. We found high levels of undescribed diversity in Trebouxia, broad distributions across distinct ecoregions for many photobiont OTUs, and varying levels of mycobiont selectivity and specificity towards the photobiont. Based on these results, we conclude that fungal specificity and selectivity for algal partners play a major role in determining lichen partnerships, potentially superseding ecology, at least at the ecogeographical scale investigated here. In order to facilitate effective communication and consistency across future studies, we propose a provisional naming system for Trebouxia photobionts and provide representative sequences for each OTU circumscribed in this study.微生物共生体对于宿主的生态适应与长期演化成功至关重要，而共生互作的核心作用正日益被绝大多数生命类群的研究证实。地衣是研究物种互作模式的经典模型系统，但地衣共生体间的亲缘关系常因物种边界模糊，或难以精准鉴定共生体而被掩盖。物种丰富的地衣型真菌科——梅衣科（Parmeliaceae）为探究不同尺度下藻类共生体的互作模式提供了极佳研究体系，本研究则在迄今最大的地理与分类学尺度上，解析了地衣共生体的互作格局。本研究共分析了2356条藻类ITS序列，这些序列来源于10个梅衣科（Parmeliaceae）真菌共生体（mycobiont）属、2个茶渍科（Lecanoraceae）真菌共生体属的地衣样本，以及20株培养的共球藻（Trebouxia）菌株。研究将藻类序列划分为操作分类单元（OTUs），并基于生态地理分布与真菌共生体的分类学特征，解析了这些地衣中共生体的互作模式。研究发现共球藻属存在大量未被描述的多样性；多数光共生体（photobiont）OTUs可广泛分布于不同生态区；且真菌共生体对光共生体的选择性与专一性水平存在显著差异。基于上述结果，本研究认为真菌对藻类共生伙伴的专一性与选择性，是决定地衣共生关系的核心因素，在本研究涉及的生态地理尺度下，其作用甚至可能超越生态环境的影响。为便于未来研究中的有效交流与术语统一，本研究为共球藻属光共生体提出了一套暂定命名系统，并为本研究界定的每个OTU提供了代表性序列。