XVI International Botanical Congess

Extant vascular plants have an aquatic ancestor or ancestors. Today they dominate the terrestrial vegetation of the world. Those which now live in water have, for a second or even third time, reinvaded water. Aquatic species are found in 418 genera from 92 families of living vascular plants. Analyzing the morphological and phylogenetic affinities of all aquatics at taxonomic levels from division to varieties of species, indicate that the event of evolving from land back to water has taken place, at least 212 times but it could have happened 252 or even more times (ferns 7 times, seed plants 204 to 245). Aquatic plants have evolved from often very different genetic and ecological backgrounds. Also, they have evolved at different times, some old ones are aquatic at the level of order or family, which others, more recent, are isolated species in otherwise terrestrial genera or races within species. It is, nevertheless, wonderful that such a large variety of plants have evolved solutions to the single problem of remastering life in water.