Abstract
Bryophytes occurring in riparian systems where they are seasonally submerged or inundated are poorly documented in many parts of the world. The actual number of rheophytic bryophytes remains speculative but we believe the number could easily exceed 500 taxa. Rheophytic bryophytes generally display highly disjunct populations and adjacent rivers and streams can have considerably different species composition. Water management in the form of flood control, dams, and hydroelectric development can adversely impact many rheophytic bryophyte species and communities due to changes in river ecology, timing of water flow, and water temperature. Specimens of rheophytic bryophytes are underrepresented in herbaria and labels rarely indicate the actual micro-habitat and ecological attributes for bryophytes collected within riparian systems. Many rheophytes are morphological anomalies compared to their terrestrial relatives and the evolution of the rheophytic condition has occurred repeatedly in many bryophyte lineages.