Specialist taxa restricted to threatened habitats contribute significantly to the regional diversity of Peltigera (Lecanoromycetes, Ascomycota) in Estonia

The widespread cyanolichen genus Peltigera comprises many insufficiently known poorly delimited and/or undescribed species. Phylogenetic analysis of 252 Peltigera specimens from a wide range of habitat types in Estonia revealed 31 putative taxa (OTUs). Multivariate analysis revealed habitat-specific segregation between the Peltigera species along a gradient from humid eutrophic forests to dry oligotrophic forests and grasslands and along a soil pH gradient from alkaline soils of alvar grasslands to acidic soils of conifer forests. The diversity of Peltigera was the highest on roadsides and dunes and the lowest in alvar habitats which, however, supported the unique assemblage of undescribed Peltigera taxa. Deciduous broad-leaved forests, too, included several undescribed or rare and red-listed species. The results demonstrate that in Estonia many Peltigera species have narrow habitat requirements and are at present threatened by habitat loss and degradation.