Wątrobowiec Frullania dilatata w Wigierskim Parku Narodowym na tle jego występowania w Polsce

This paper presents the distribution of Frullania dilatata in Wigry National Park (north-eastern Poland) based on studies conducted during the period 2012–2018. The liverwort was documented at 43 localities (arranged in relation to the MGRS 100 × 100 m grid system) and at 188 inventory sites (trees and shrubs). Most of the stations (54%) were observed on the bark of hazel (Coryllus avelana), which is a unique feature throughout the country. On the basis of literature data from Poland (830 localities), the current threat to this species was analysed. The habitat characteristics of Frullania dilatata in the Wigry National Park and throughout the country are presented.