Riccia crustata
Riccia crustata Trab.
Ricciaceae
Conservation status. Critically Endangered [CR B2ab(iii)]. The species is listed in the Red Data Book of European Bryophytes as “Vulnerable”.
Morphology and biology. Annual thalloid liverwort forming irregular rosettes 2–4 mm long and about 1 mm wide with deep and narrow channel in the middle. When fresh, the thallus is bluish green, when dry whitish and fragile. Using hand-lens, the grainy surface is clearly visible because of the spherical, calcium carbonate-covered epidermal cell wall projections. Fertile plants were not found in Bulgaria.
Habitats and populations. Plants grow on exposed calcareous soils in lax herb and shrub habitats with Juniperus oxycedrus in shrub layer. The populations are characterized by limited distribution, low cover, low growth rate, and density fluctuations related to climate dynamics (succession of dryer and wetter years).
Distribution in Bulgaria. Pirin Mts (Southern – the hill eastwards of Nova Lovcha village, Gotse Delchev district).
General distribution. Balkan Peninsula (Bulgaria), France, Estonia, Belarus, N Africa, C and W Asia. Mediterranean species.
Threats. Trampling, plough up for agriculture activities, afforestation, air pollution. Ceasing grazing with concomitant trees and shrubs succession causes a loss of appropriate microhabitats such as calcareous soils with lax herb vegetation.
Conservation measures taken. The locality is in a site of the European ecological network Natura 2000 in Bulgaria.
Conservation measures needed. Studies on population dynamics and growth rate; legal protection of the species; designation of the locality of the species which is also a locality of Mannia triandra (a species listed in the Habitats Directive and Biological Diversity Act) as a protected area.
References. Petrov 1966a.
Author: Anna Ganeva
