The great bulk of the world’s charophyte literature of the past 100
years or more suffers from several major limitations. Much is entirely
descriptive with but few attempts to ascribe any functionality to the features
under consideration, or how they adapt such species to their respective
ecological niches. Charophyte distributions have been attributed almost
entirely to physical parameters with virtually no consideration given to the
role of aquatic herbivores or other biotic environmental factors. Furthermore,
most workers have focused on relatively restricted areas with little or no
reference to others either near or far removed. That there is much to be
gained from a wider focus (both spatially and conceptually) that incorporates
greater conjecture as well as enhanced collaboration is here suggested. How
are the charophyte floras of one region similar to, or different from, those
of another, and, of particular significance,
‘Why?’ The authors, being North American,
focus on that continent but with the firm conviction that most generalities
applicable there hold equally true for other landmasses, and have done so for
the previous 10, if not 100, million years. This account focuses first, if
somewhat superficially, on 14 widely distinct North American charophyte
communities (plus South American Lake Titicaca) and then in greater detail on
four of those. Among other issues considered are how species richness relates
to latitude; why some geographical entities support more charophyte species
than do others; the extent to which charophyte floras reflect the availability
of different habitats; the contributions of herbivory to the preceding; the
stability of the North American charophyte flora; the ecological
considerations most often reflected by charophyte zonation and how–or to
what extent–range extensions reflect niche preferences or requirements.
While the authors well appreciate just how minimal their efforts may appear a
century hence, at least they hope to have placed on the table some
considerations with which colleagues from other landmasses may agree, disagree
or suggest modifications.