Hornworts in Switzerland—endangered?

Maps of the distribution of Anthoceros punctatus L. var. cavernosus auct. and Phaeoceros laevis (L.) Prosk. ssp. carolinianus (Michx.) Prosk. in Switzerland are presented. They are based on herbarium specimens and field studies and distinguish between records before and since 1960. According to bibliographical data from the beginning of this century, both taxa were widespread throughout Central Europe, A. punctatus being more common than P. laevis. This view is not supported by herbarium collections. Detailed field research from 1981 to 1989 in the vicinity of Berne showed that the occurrence of hornworts depends largely on the type and treatment of cultivation. P. laevis seems to be more sensitive to changes in habitat conditions caused by modern agricultural practice (mechanical stress, increase in fertilizer input and use of pesticides) than A. punctatus. In conclusion, P. laevis is classified as endangered in Switzerland.