Impact of land use on populations of Vertigo moulinsiana (Dupuy, 1849) and Vertigo angustior (Jeffreys, 1830) (Gastropoda: Pulmonata: Vertiginidae): Ilanka River valley (W. Poland)

Many sedge meadows in western Poland provide suitable habitats for Vertigo angustior Jeffreys and Vertigo moulinsiana (Dupuy) which are regarded as threatened across Europe. Such habitats are often subject to conservation measures aimed at supporting wetland birds in accordance with the European Birds Directive. Such measures, usually involving extensive mowing, may not favour the vertiginids. Both species are protected by another European act – The Habitats Directive. The range of methods used for maintaining the bird habitats is wide: the sites are mowed manually or mechanically in different ways, and the mowing covers the entire site or just selected patches. The aim of this study was to check how the different maintenance methods influenced the vertiginid populations. The abundance of V. angustior and V. moulinsiana was studied at 17 sampling sites along the Ilanka river valley (Lubuskie Province, W. Poland). The sites differed in size, moisture level, vegetation, type of land use and shadiness. The results suggest that extensive land management can be advantageous for botth species only when the site is divided in patches which are mowed alternately in consecutive years.