Late pleistocene and holocene history of genus isoetes L. (Lycopodiophyta) in the Western Rhodope Mountains, Bulgaria. New palynological and palaeoecological data

The genus Isoetes is represented in Bulgaria by one species I. lacustris L. (lake quillwort). It inhabits the littoral areas of some lakes in the Pirin Mountain range. Fossil records of Isoetes in Bulgaria are very scarce. A new palynological study was conducted on sediments collected from Kupena Mire in the Western Rhodope Mountains. The results indicated that lake quillwort was abundant 30 000 years ago and its growth was associated with the presence of shallow lake basins. The species disappeared from the composition of the local flora as the sedimentation regime changed from lacustrine to marsh after the warming of the climate at the onset of the Holocene. This study confirmed the existence of refugial areas during the last glaciation in the mountains of Southeastern Europe, where a number of glacial relics had survived.