Die Wasserschlauch-Arten im oberen Glatttal, Kanton Zürich, mit besonderer Berücksichtigung von Utricularia stygia Thor

Abstract

Occurrence and distribution of Central European bladderworts (Utricularia spp.) have been studied in the upper Glatt Valley (Canton of Zurich, Switzerland), with special reference to U. stygia Thor. Due to the taxonomic problems in this genus the identification of the species is largely based upon reproductive and micromorphological characters such as the leaf margins and the quadrifids inside the traps. For five species regional maps and photographs of flowers are presented. Morphological characters of U. stygia and U. intermedia are documented in detail. It is suggested that the historical records of U. ochroleuca Hartman in Switzerland refer today to U. stygia Thor, and it is questionable whether U. ochroleuca sensu stricto has ever been collected here. Recent decline of Utricularia spp. in the Swiss Plateau and its causes are outlined and recommendations for suitable habitat management are given to secure long-term survival of the rare Utricularia species in Switzerland. Special attention is paid to cooccurrence of Utricularia stygia, U. intermedia, U. minor and the damselfly Nehalennia speciosa, all exhibiting similar habitat requirements.