Viola elatior, V. pumila and V. stagnina in Austria, Czechia and Slovakia: a story of decline.

Specimens of Viola elatior (VE), V. pumila (VP) and V. stagnina (VS) in 40 Austrian, Czech and Slovak public herbaria were revised, a total of almost 1750 specimens from the three countries. Apart from VE, the quality of the original identifications was rather poor, especially of VS, which was frequently confused with VP and V. canina. This, together with the confusion of nomenclature that persisted during the 19th century, made the old literature records unreliable. Hybrids are usually difficult to identify and are rarer than generally believed. VS and VP have similar distribution patterns: they occur mainly on floodplains of large lowland rivers and in adjacent hills in the N part of Bohemia, S and Central Moravia, E Austria and S Slovakia; they may be classified as river corridor plants. VS differs from VE and VP mainly by its presence in S Bohemia and its absence from large parts of S Slovakia, as well as its rarity in Austria and Slovakia. All three species grow predominantly in regions with a relatively warm and dry climate: most localities are situated in regions with a mean annual temperature of 7–11 °C and mean annual precipitation 401–700 mm. A temporal analysis of records revealed that all three species are declining in all three countries: generally, this decline is weakest in Austria, with 46–61% of grid cells with occurrences confirmed after 1980 (compared with the number of grid cells with records for 1801–2008), and strongest in Slovakia, with 18–32% of grid cells with occurrences confirmed after 1980. The decline is due mainly to the canalization of rivers and subsequent changes in land use, urbanization and recently afforestation. VE may also be endangered by modern forestry practices. The inclusion of all three species in national Red Lists and subsequent conservation measures are justified and necessary, though national Red List status may differ between countries.