The role of hydrochory in structuring riparian and wetland vegetation

• Hydrochory, or the passive dispersal of organisms by water, is an important means of propagule transport, especially forplants. During recent years, knowledge about hydrochory and its ecological consequences has increased considerablyand a substantial body of literature has been produced. Here, we review this literature and define the state of the art ofthe discipline. A substantial proportion of species growing in or near water have propagules (fruits, seeds or vegetativeunits) able to disperse by water, either floating, submerged in flowing water, or with the help of floating vessels.Hydrochory can enable plants to colonize sites out of reach with other dispersal vectors, but the timing of dispersaland mechanisms of establishment are important for successful establishment. At the population level, hydrochorymay increase the effective size and longevity of populations, and control their spatial configuration. Hydrochory isalso an important source of species colonizing recruitment-limited riparian and wetland communities, contributing tomaintenance of community species richness. Dispersal by water may even influence community composition in differentlandscape elements, resulting in landscape-level patterns. Genetically, hydrochory may reduce spatial aggregation ofgenetically related individuals, lead to high gene flow among populations, and increase genetic diversity in populationsreceiving many propagules. Humans have impacted hydrochory in many ways. For example, dams affect hydrochoryby reducing peak flows and hence dispersal capacity, altering the timing of dispersal, and by presenting physical barriersto dispersal, with consequences for riverine plant communities. Hydrochory has been inferred to be an important vectorfor the spread of many invasive species, but there is also the potential for enhancing ecosystem restoration by improvingor restoring water dispersal pathways. Climate change may alter the role of hydrochory by modifying the hydrology ofwater-bodies as well as conditions for propagule release and plant colonization.

Nyckelord

landscapes

plant dispersal

plants

propagules

restoration

rivers

species richness

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