Water Plants
The land plants, from mosses to flowering plants, all share an aquatic ancestor that left the water to conquer new territory. Today's aquatic plants all had terrestrial ancestors that changed their minds: they left the land and re-adapted to life in the water.
Among the land plants, 103 families and 440 genera include aquatic species (Cook 1999). Only about 2% of angiosperm species are aquatic, but across the angiosperms, aquatic lifestyles are estimated to have evolved at least 200 times (Cook 1999). Add in some aquatic ferns and lycophytes, and the aquatic tracheophytes are a fascinatingly diverse group.
Useful references:
Cook CDK. 1999. The number and kinds of embryo-bearing plants which have become aquatic: a survey. Perspectives in Plant Ecology, Evolution and Systematics 2: 79–102. https://doi.org/10.1078/1433-8319-00066
Cook CDK. 1990. Aquatic Plant Book. SPB Academic Publishing, The Hauge, The Netherlands. 228 pages.
Meseguer AS, Carrillo R, Graham SW, Sanmartín I. 2022. Macroevolutionary dynamics in the transition of angiosperms to aquatic environments. New Phytologist. 2022 Mar 16. https://doi.org/10.1111/nph.18100
Philbrick CT, Les DH. 1996. Evolution of aquatic angiosperm reproductive systems. Bioscience 46(11): 813-26.
Rataj K, Horeman TJ. 1977. Aquarium Plants: Their Identification, Cultivation and Ecology. TFH Publications, New Jersey, USA.
