In June 2015 the best possible alvar study sites and other habitats in Estonia were selected. Nearly 300 hundred Peltigera samples with both mycobiont and photobiont sequences were characterized. Phylogenetic analyses of ITS sequences revealed previously undetected diversity especially within the Peltigera canina group. Direct ordination methods were used to assess the significance of associations between phylogenetically identified lichen taxa and environmental variables. Multivariate analysis revealed habitat-specific segregation between Peltigera species along a moisture gradient from humid eutrophic forests to dry oligotrophic forests and grasslands. Changes in species composition were also found along a soil pH gradient form alkaline soils of alvar grasslands to acidic soils of conifer forests.
Using nucleotide differences in the tRNALeu (UAA) intron more than 30 different symbiotic Nostoc genotypes were identified. In studied habitats we found the highest number of symbiotic Nostoc haplotypes in alvar grasslands and dunes. However, genetic diversity of Nostoc haplotype was the highest in roadside grassland and on ground of eutrophic forest. Some Peltigera taxa associated with a single or a few closely related Nostoc genotypes, others were generalists, being able to associate with a spectrum of different Nostoc genotypes. The association of different Nostoc haplotypes of studied Peltigera taxa is not necessarily correlated with mycobiont taxonomy instead seems to be correlated to environmental factors.
In addition, environmental factors and ground disturbance affecting the composition of species and functional traits of ground layer lichens on grey dunes and dune heaths of Estonia were analyzed. Several Peltigera species were revealed to be characteristic species for grey dunes and lichens with cyanobacterium as the main photobiont favored grey dune habitat. It was concluded that to protect and conserve the species-rich lichen biota, it is necessary to protect the dune habitats from building activity, to avoid over trampling in recreation areas and to regularly remove shrubs and trees.
Locality data of rare and protected species (Peltigera, Solorina) will be deposited and stored in EELIS (Estonian Nature Information System). Moreover, the evaluation of host tree preferences of red-listed epiphytic lichens, including cyanolichens, was performed. The highest number of red-listed species were accounted for Fraxinus excelsior, Quercus robur and Populus tremula. It was revealed, that several taxa, mainly the cyanolichens, prefer P. tremula to other trees, confirming its high importance as phorophyte species for the threatened epiphytes. Populus tremula can be conisidered as the best possible altervnative phorophyte for the gratest part of threatened lichen species that are growing on temperate broad-leaved trees.
