Riccia papillosa
Riccia papillosa Moris
Ricciaceae
Conservation status. Endangered [EN B2ab(iii)c(ii)].
Morphology and biology. Annual thalloid liverwort forming comparatively regular bluish green rosettes. Thallus lobes 4–5 mm long and 0.5–1 mm wide, with narrow channel. Upper part of the thallus is covered with large, thick, colourless, often hook-shaped papillae. The cover tissue is of a 2-cells layer, the upper with spherical cells; ventral scales are colourless, soon vanishing. Spores blackish brown, its surface areolate. Unisexual.
Habitats and populations. Plants grow on bare soil in lax herb and shrub communities in oak forest belts. Changes in population density could be observed over the years if there is lack of appropriate ecological conditions for species development. The species is characterised by limited distribution and low growth rate.
Distribution in Bulgaria. Sofia Region (Iskar River valley between Kokalyane and Gorni Pasarel villages), Slavyanka Mt (Petrovska River valley and along the road between Petrovo and Goleshevo villages).
General distribution. Balkan Peninsula (Bosnia and Herzegovina, Bulgaria, Croatia, Greece, Montenegro, Romania, Serbia) and other parts of Europe (France, Portugal, Canary Islands, Hungary, Estonia, Ukraine, Crete), N Africa, Middle and W Asia. Sub-Mediterranean species.
Threats. Agriculture activities (farming, plough up of agriculture lands), afforestation, soil pollution, building activities, succession of shrubs and trees, climate change. Ceasing grazing results in overgrowth of shrubs and trees and lost of suitable microhabitats such as exposed soils with lax herb vegetation.
Conservation measures taken. Some localities are within sites of the European ecological network Natura 2000 in Bulgaria.
Conservation measures needed. Studies on population dynamics and growth rate using monitoring sampling plots in more vulnerable and less vulnerable localities.
References. Petrov 1963.
Author: Anna Ganeva
