Current knowledge about Sorbus gemella

Sorbus gemella is a stabilised apomictic species endemic to Czechia. It originated by hybridisation between S. torminalis and probably S. danubialis, and occurs in the Džbán region in north-western Bohemia. The species was described in 1996 and to date very little was known about its population size. A detailed survey of its distribution carried out in 2018–2021 showed that the number of individuals of the species is at least 1,500, which makes it the second most abundant endemic Sorbus species in Czechia. Despite the relatively high number of individuals, the species is critically endangered, mainly due to the geographically limited distribution range, aging of the populations, and the unfavourable state of its habitats. Sorbus gemella is endangered by spontaneous colonisation of open habitats (especially open-canopy forests) by trees, and by wild herbivore grazing. The traditional management of woodlands in the area used to include maintaining open-canopy and oligotrophic forests, which are the main habitat of the species. The closed canopy which prevails in present-day forests is unfavourable for survival in the long term and for regular reproduction of this light-demanding species. Particular attention should be paid to active protection of the species in the future. Building fences for the protection of seedlings, reduction of game populations, and appropriate forest management should be implemented. A distribution map, an improved description of the species, a list of studied herbarium specimens, comments on the origin, reproduction, and biology of the species’, and other relevant information are provided. The paper also includes a line drawing and photographs of the species and a photograph of the type specimen.