Chapter 1: The Characeae Plant

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what has been described as a species with a genetically discrete ‘clade’ or group of
individuals is one of the frontiers of taxonomy today. Traditionally characeae species have
been organised into groups within a genus (subgenera, sections, subsections) and ‘complexes’
of closely related species have been recognised. A charophyte ‘species complex’ is a group of
morphologically similar, closely related taxa that have, historically, had the morphological
extremes described as different species by some authors (e.g. Braun and Nordstedt 1882), and
described as different varieties or forms by other authors (Wood 1965; Boegle et al. 2007;
Blume et al. 2009). Examples of these are the Nitella hookeri complex of Australia and New
Zealand (Casanova et al. 2007) and the Chara baltica complex of central Europe and the
Baltic Sea (Boegle et al. 2007; Blume et al. 2009).
Historically the first comprehensive taxonomic treatment on characeae was by Braun and
Nordstedt (1882), and was based on the specimens from around the world available to those
experts at the time. They distinguished between the genera Chara and Nitella, but the other
genera were not delineated and named until later in the 19 th (Tolypella, Lychnothamnus,
Nitellopsis) or 20 th centuries (Lamprothamnium). Researchers in the past often saw few
specimens of each species, so the conclusion that many characeae ‘species’ had a broad range
of characteristics was a natural conclusion. Subsequent taxonomists used Braun and
Nordstedt (1882) as a basis for their taxonomy (Zaneveld 1940, Wood 1962), but it was not
until 1965 that a world-wide treatment of family Characeae was attempted. Wood (1965)
tried to rationalise the species concept in Characeae, amalgamating monoecious and
dioecious species and grouping morphologically similar specimens from around the world.
His work resulted in a reduction of the 350 recognised species to just 18 species of Chara,
three of Lamprothamnium, 90 of Nitella, three of Nitellopsis and two of Tolypella.
Subsequent research has shown Wood’s species concept to be erroneous, and rather than
there being c. 180 species in family Characeae, the older treatments (c. 380 species) give a
better representation of the true diversity. This has consequences for physiologists seeking to
identify charophytes. Firstly Wood’s work resulted in confusion rather than consensus among
taxonomists. Long-held species concepts had been demolished and in many places in the
English-speaking world Wood’s treatment was accepted without challenge. Few people using
Wood’s taxonomy were able to reliably identify characeae to species. This was especially
true for some of the species most frequently used by physiologists: Chara
australis/corallina/inflata, Lamprothamnium macropogon/paulosum/succinctum. With the
use of molecular taxonomy (e.g. McCourt et al. 1996) and an experimental approach to the