Search

The genus Hydrocharis L. includes free-floating, occasionally rooted obligate pleistophytes and rooted hydrohelophytes, which are edificators and subedificators in freshwater vegetation communities. How ecologically similar are these closely related species? It has been established that Hydrocharis dubia (Blume) Backer. and H. morsus-ranae L. are facultatively freshwater alkaliphilic mesoeutrophic ortho- and mesoalluviophilic detrito- and psammopelophiles. H. chevalieri (De Wild.) is ecologically isolated; it is a freshwater acidoneutrophilic meso-, mesoeutrophic, ortho-mesoalluvialophilic species indifferent to the mechanical composition of bottom sediments. The coenocomplex of H. chevalieri is characterized by the abundance of helophyte communities; the key role in the composition of the coenocomplex of two other species is played by hydatophyte and pleistophyte communities. Communities with species of the genus Hydrocharis have simple synmorphology, a relatively high species richness, and a high proportion of low-abundance species. [ABSTRACT FROM AUTHOR]

Hydrilla verticillata (L. f.) Royle is a hydatophyte with a disjunctive semicosmopolite range playing a significant role in the functioning of aquatic ecosystems. The structure of the coenocompleх of the species in northern Eurasia includes 19 associations belonging to 17 formations of the freshwater macrophyte vegetation. Ninety-one species of hydromacrophytes have been recorded as part of the phytocoenosis with the participation of H. verticillata. Associations Hydrilla verticillata (Northern Eurasia) and Nymphaea candida— Ceratophyllum demersum + Hydrilla verticillata (Eastern Europe and Western and Central Siberia) have the widest geographical range. This paper describes the tolerance limits of H. verticillata to major abiotic factors: type of bottom soil, flow rate, trophicity, saprobity, alluviality, and content of main ions of dissolved salts and soluble forms of heavy metals in the water. In environmental terms, H. verticillata should be regarded as a freshwater alkaliphylic oligo-mesotrophic oligo-β-mesosaprobic mesoalluvialitic psammopelophyt. [ABSTRACT FROM AUTHOR]