Invasion of Eragrostis albensis in Central Europe: distribution patterns,taxonomy and phylogenetic insight into the Eragrostis pilosa complex

The Eragrostis pilosa complex (Poaceae) comprises five widely distributed and regionally invasive species—E. albensis, E. amurensis, E. imberbis, E. multicaulis, and E. pilosa, distinguished by tiny and variable morphological characters and with so far unknown phylogenetic relationships. Recently, some doubts have been raised about the status of an invasive glandular morphotype occurring in Central Europe assigned either to E. amurensis or to E. albensis. Here, we addressed this issue by analysing morphology, internal transcribed spacers of nuclear ribosomal DNA, and five inter-simple sequence repeat markers. The genetic evidence supported closer relationship of this glandular morphotype to eglandular E. albensis, widely established in Central Europe, than to glandular E. amurensis described from Asia. We propose to adopt a new taxonomic treatment that E. albensis includes both eglandular and glandular individuals, and to classify the glandular ones as E. albensis var. scholziana M. Nobis & A. Wróbel var. nova. Currently this new taxon is known from a dozen of localities in Central Europe and is invasive in the lower section of the Oder River valley, whereas Eragrostis albensis var. albensis has already spread widely across Europe in riparian phytocenoses and anthropogenic habitats. Since probably the first registered records in 1940s, it has been observed in European part of Russia, Belarus, Ukraine, Poland, Slovakia, Czech Republic, Germany, Austria, the Netherlands, and its further invasion is likely to proceed. We provided distribution maps concerning spread dynamics of E. albensis in Europe from 1947 to 2020. In total, the species has been observed on over 1300 localities so far, most of which were found after 2000.