Peltigera lichens are bi- or tripartite associations widespread in several environments worldwide. In Chile, only bipartite Peltigera in association with Nostoc cyanobacteria as photobiont are reported. The level of specificity in the lichen association can be determined by elucidating the number of photosynthetic partners joined to one mycobiont species, which could be classified from strict specialist to broad generalist. Here, we studied the genetic diversity of 311 Peltigera specimens collected in forests and grasslands from the Coyhaique National Reserve and the Patagonia National Park (300 km away), and we evaluated their specificity. The mycobionts identity was confirmed by analyzing fungal LSU and ITS sequences, while cyanobionts were grouped in haplotypes (identical sequences) according to their SSU sequences. We found 10 Peltigera species, including a new species yet not described from the P. rufescens clade, associated with 24 different Nostoc haplotypes. In forests, the most abundant species were P. fuscopraetextata and P. frigida, while P. antarctica and P. rufescens predominate in grasslands. Nostoc H07 was the most common haplotype (45%), but it was only associated with P. fuscopraetextata and P. frigida. Some species (e.g. P. frigida and P. truculenta) were highly specific and were associated with only one or few Nostoc haplotypes, while others (e.g. P. antarctica, P. fuscopraetextata and P. aubertii) were associated with up to 6 different Nostoc haplotypes. Although some Nostoc haplotypes were widely distributed, most of them were only found in a specific environment, being several Peltigera species associated with the same Nostoc haplotype at each site. Altogether, these results suggest that the association patterns among lichen symbionts would be environmentally structured rather than phylogenetically constrained by the mycobiont identity, supporting functional lichen guilds as reported in other studies of cyanolichens. Funding: JO (FONDECYT-1181510), KA (ANID-PCHA/Doctorado Nacional/2016-21160637).
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