Distribution, state of population and other knowledge of Sorbus rhodanthera, an endemic tree from western Bohemia

Sorbus rhodanthera was described in 1996 as endemic to the Chlumská hora hill in the surroundings of the town of Manětín in western Bohemia, Czech Republic. It is an apomictic hybridogenous taxon of the subgenus Tormaria, with the assumed parentage of S. torminalis and S. danubialis or S. collina. In 2014–2020 we surveyed in detail its distribution. Sorbus rhodanthera occurs mainly on Chlumská hora hill and rarely on nearby Doubravický vrch hill. The total number of individuals including saplings taller than 1 m is 741. The distance between the two most remote individuals is 4.9 km and distribution of this species covers area of 390 ha. It mainly grows in open forests including both semi-natural vegetation of the alliances Carpinion betuli and its transition to Quercion roboris or Quercion pubescenti-petraeae, and in Pinus sylvestris, Larix decidua plantations and their clearings. It was rarely recorded also in woodland communities of the Tilio platyphylli-Acerion alliance, edges of screes and other tree plantations and on rocks. Sorbus rhodanthera is endangered by wild herbivore grazing (seedlings and saplings are rare and often damaged) and by spontaneous colonization of open habitats (especially open-canopy forests) by trees. The traditional management of woodlands in the area used to maintain open-canopy and oligotrophic forests, which are the main habitat for the species. The closed canopy, which prevails in present-day forests, is unfavourable for a long-term survival and regular reproduction of this light demanding species. Particular attention should be paid to active protection of the species in the future. Building fences for protection of seedlings, reduction of game population, and appropriate forest management should be implemented especially in the Chlum Nature Reserve. A distribution map, improved description of the species, list of all studied herbarium specimens, comments on the species’ origin, reproduction and biology and other relevant information are provided. The paper also includes a pen drawing and photographs of the species and a photograph of the type specimen.