The identity of the North American endemic Dendriscocaulon intricatulum and two southern South American cyanomorphs in the Peltigerales

Lichen photomorphs refer to distinct symbiotic structures formed by conspecific fungi associated with different photosynthetic partners, either a green alga or a cyanobacterium. Thus, a single fungal species can engage in symbiotic relationships with different photobionts, resulting in independent, often morphologically distinct, lichen thalli. Historically, the morphological dissimilarity between photomorphs has often led to their classification as separate fungal species, which could even have been accommodated in different genera. However, molecular data have played a crucial role in revealing the genetic similarity and conspecific nature of the fungi composing these photomorphs. In this study, we employed a phylogenetic framework to validate the conspecificity of photomorph pairs within three species indigenous to the Americas: Nephroma kuehnemannii, Ricasolia quercizans and Sticta ainoae. Consequently, Nephroma microphyllum is considered a synonym of N. kuehnemannii, Dendriscocaulon intricatulum a synonym of R. quercizans, and free-living Chilean dendriscocauloid lichens are shown to be cyanomorphs of S. ainoae. A species distribution modeling approach to investigate the geographical distribution and niche characteristics of photomorphs within R. quercizans in eastern North America revealed that its two photomorphs exhibit distinct distributions and ecological niches, suggesting potential adaptations to different environmental conditions. The confirmed conspecificity and niche variation among the considered photomorphs provide insights into the ecological and evolutionary dynamics of these symbiotic associations.