Freshwater bryozoans: a zoogeographical reassessment

Significant changes have occurred since the publication of Bushnell’s 1973 paper on the zoogeography of freshwater bryozoans. There have been important new field surveys:, the number of recognized species has nearly doubled and the taxonomic foundation is much more solid. Taxonomic revisions and the re-examination of misidentified material have diminished the reported ranges pf many species. Such nolonger-widespread species include Plumatella emarginata, P. repens, P. longigemmis, Stolella indica, Fredericella sultana , and Gelatinella toanensis . An assumption of dispersal by migrating waterfowl explains the narrow, intercontinental ranges of several species. In other instances the dispersal patterns suggest human activities as a major contributing factor. Some species are clearly more vaglie than others for reasons currently unknown. Asia, Africa, and South America are still largely unexplored for freshwater bryozoans. Nearly half of all known species are reported from only one or two collections. At a time when extinctions among freshwater animals have reached an unprecedented high rate, endemic bryozoan species may warrant special vigilance and protection. New initiatives are needed to inventory species in large, unexplored regions.