Rozšíření druhu Hamatocaulis vernicosus (Calliergonaceae) v České republice

The historical and recent distribution of Hamatocaulis vernicosus, a species of Annex II of the Habitats Directive, was studied on the basis of herbarium specimens, a review of published literature and the authors’ own survey of potentially suitable biotopes. The species has been recorded recently at 54 localities, while its occurrence was not verified at 75 historical localities supported by specimens, and at 14 unsupported localities. Population size ranges from a few stems to tens of square metres most of the populations are considered to be adversely affected by various negative factors including unstable water regime, eutrophication, lack of appropriate management, expansion of woodland and other successional changes.