Species diversification and phylogenetically constrained symbiont switching generated high modularity in the lichen genus Peltigera

1. Ecological interactions range from purely specialized to extremely generalized in nature. Recent research has showed very high levels of specialization in the cyanolichens involving Peltigera (mycobionts) and their Nostoc photosynthetic partners (cyanobionts). Yet, little is known about the mechanisms contributing to the establishment and maintenance of such high specialization levels. 2. Here, we characterized interactions between Peltigera and Nostoc partners at a global scale, using more than one thousand thalli. We used tools from network theory, community phylogenetics and biogeographical history reconstruction to evaluate how these symbiotic interactions may have evolved. 3. After splitting the interaction matrix into modules of preferentially interacting partners, we evaluated how module membership might have evolved along the mycobionts’ phylogeny. We also teased apart the contributions of geographical overlap vs phylogeny in driving interaction establishment between Peltiger...

1. 生态相互作用在本质上呈现从严格特化到极度泛化的连续谱系。已有研究表明，包含肺衣属（Peltigera，真菌共生体mycobionts）与其念珠藻属（Nostoc，光合蓝藻共生体cyanobionts）的蓝藻地衣（cyanolichens）中，存在极高程度的特化互作模式。然而，目前学界对这类高度特化关系的建立与维持机制仍缺乏深入认知。
2. 本研究依托逾1000份地衣体（thalli）样本，在全球尺度下解析肺衣属与念珠藻属共生伙伴间的相互作用特征；我们运用网络理论（network theory）、群落系统发育学（community phylogenetics）及生物地理历史重建（biogeographical history reconstruction）等分析手段，探究此类共生相互作用的演化路径。
3. 本研究先将相互作用矩阵划分为由偏好性互作伙伴构成的功能模块，进而评估真菌共生体的系统发育历程如何影响模块归属的演化模式；同时我们还厘清了地理分布重叠与系统发育关系在驱动肺衣属物种间互作建立过程中的相对贡献……