Populations of Knautia in ecologically distinct refugia on the Hercynian massif belong to two endemic species.

Comprehensive taxonomic studies in which a combination of molecular, cytogenetic, morphological and ecological approaches are used have resulted in remarkable discoveries even in well-known floras. In particular, recognition of new local endemics has important implications for conservation and management of plant diversity. Due to Quaternary climatic oscillations, the vascular flora of the Czech Republic only includes a few endemic taxa, usually microspecies with an apomictic mode of reproduction. Here we re-evaluate the taxonomy of Knautia arvensis, an intricate eco-geographically differentiated diploid-polyploid complex, and identify two new sexual species endemic to central Europe, which were previously included in the polymorphic K. arvensis. While K. serpentinicola Smejkal ex Kolář, Z. Kaplan, J. Suda et Štech is a diploid and tetraploid species restricted to four isolated serpentine areas in the Czech Republic and Germany, diploid K. pseudolongifolia (Szabó) Żmuda is known from a single subalpine site in the Krkonoše Mts. Our investigation of 38 populations of K. arvensis s. str. and the two newly recognized species sampled across eastern central Europe revealed a distinct yet incomplete (i.e. confounded by phenotypic plasticity) morphological differences between the three species. These results together with available data on cytological (distinct nuclear genome size), genetic (independent evolutionary histories) and ecological (distinct ecological preferences) variation support an independent taxonomic status for the newly described species. Our study highlights the importance of ecologically stable habitats where plant competition is not severe (Holocene refugia) for preserving unique plant diversity. In addition, it demonstrates the value of multi-disciplinary taxonomic research even in botanically well-known areas.