Modern Taxonomic Rhododendron Grouping
Rhododendron ABC's #5
Okay! This is it! You probably are thinking "no more nomenclature dissertations", but, please bear with me one more time! I want to summarize the modern rhododendron taxonomic schemeand then I promise to go on to other rhododendron topics.
As I have mentioned before, the so-called artificial series system devised by Balfour in the UK sufficed for many years to bring some order into describing the Genus. It will probably be with us for a long time. Mr.H. H. Davidian,of the Royal Botanic Garden in Edinburgh, Scotland and who is one of the most respected rhododendron authorities, still uses the series system and is quite comfortable with it.
If you are inclined toward using the most modern thinking, however, you should become familiar with the scheme first proposed by Dr. Sleumer in the Netherlands and further developed by Cullen and Chamberlainin the UK and by Spethman in Germany.
These authorities, recognizing the large size and complexity of the Genus Rhododendron, have also broken it into a number of sub-units, just as Balfour did in his nearly arbitrary manner. This recent work, however, is based on detailed study of the traits, both botanical and sometimes chemical, of each species and proposes a rather complex-seeming hierarchy of groups between genus and species. The highest of these ranks is the subgenus and eight of these are now recognized. In certain subgenera, there are only very few species, but others have many and have been further divided into sections. Just as with subgenera, some of the sections are small and not further subdivided, while others contain many species and are divided into subsections.
This scheme, although it seems complicated, is really an approach to bringing rhododendron classification into a natural, Linnaean-type system. If you want to learn more about the newer work, I suggest that you read the articles by James Cullen, either in the January 1993 Rhododendron Species Foundation Newsletter or in the 1992 Rhododendron Handbook of the Royal Horticultural Society. If you can read German, I recommend the 1991 book by fellow member, Erhard Moser, on Rhododendrons and Hybrids. In this, he mentions, and relies on, Spethman's taxonomic work utilizing chemical analyses of species differences and affinities.
It turns out that most modern authorities are "lumpers" and the number of species is not as large as once was assumed. The number is still quite large and, even with the "lumpers" ascendant at the moment over the "splitters", there are over 800 recognized species in the Genus Rhododendron.
Remember, there are two ways to subdivide the Genus:
1. By naming 40 or so series in the Balfourian scheme and assigning each species to its series, based on its affinity to the type species of the series, or
2. By assigning each species to a natural order: subgenus, section, subsection.
The latter way is more complicated, but has the advantage that one call be pretty systematic about the taxonomy of this complicated Genus!
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