Riccia crystallina
Riccia crystallina L. emend. Raddi
Ricciaceae
Conservation status. Endangered [EN B2ab(iii)c(ii)].
Morphology and biology. Annual thalloid liverwort. Plants light green or yellowish green, forming rosettes to ca. 2.5 cm diameter. Thallus 2–3 times dichotomously branched, wide cuneiform, 5–10 mm long and 2–3 times as wide as thick. During growth, the outer tissue is destroyed, giving the upper thallus layer a spongy appearance. Propagation organs (antheridia and archegonia) and sporophytes are immersed in the thallus close to its upper layer. The sporophytes become mature in winter or early spring. The spores are yellowish brown, areolate (with small angular-shaped areas on surface). Bisexual.
Habitats and populations. Plants grow on moist and exposed clay soil on channel beds, also on mire margins and flooded areas. The species can be found in lax herb and shrub communities. During the years, changes in population density could be observed if there are no ecological conditions suitable for the species’ development. The species is characterized by limited dispersal potential and low growth rate.
Distribution in Bulgaria. Forebalkan (Western – at the foot of the Vrashka Chuka peak), Sofia Region (Sofia and the Iskar River valley between the villages Kokalyane and Gorni Pasarel), Valley of Struma River (Southern – Strumitsa River valley).
General distribution. Balkan Peninsula (Albania, Bulgaria, Croatia, Greece, Montenegro, Serbia), Europe, N and Tropical Africa, Siberia, W Asia, China, India, Australia, New Zealand. Mediterranean species.
Threats. Trampling, ploughing for agriculture activities, afforestation, soil contamination, building activities near species localities, successions towards shrubs and trees.
Conservation measures taken. The locality in the Forebalkan is within the Vrashka Chuka Protected Site.
Conservation measures needed. Studies on population dynamics and growth rates using sample plots for monitoring in both more vulnerable and less vulnerable localities.
References. Stefanoff & Petrov 1962, Petrov 1963, Šmarda 1970.
Author: Anna Ganeva
