Quote: >But there are times when I really have to know the "right" name for an orchid >and these fluctuations are driving me batty.
It is a time of massive upheaval. There was a multi-gene assessment of relatedness amongst the birds published last week in AAAS Science: the passarines - Sparrows, finches - now have a new close relation: the parrots. Ostriches have been ejected from the rest of the birds but have acquired the tinamous; and their closest relations are the ducks. And so it goes on. I suspect that people who label colour forms are carrying out the equivalent of renaming suburban streets when the entire city is about to be re-zoned, or perhaps even the nation. My guess about orchids is that the intensely split genera - the Asian monopodials, to name one over-defined area - will be lumped, and that genera with finely split species (Paphiopedilums, Phalaenopsis to stay with the Asian theme) will also be lumped. I name not names, but just because two forms of something can be distinguished by minor markers does not usefully make them species! (Or, from a commercial point of view, perhaps it does.) Dendrobium and Bulbophyllum truly need to be split if one's brain is not to burst, but the dotted lines along which this should be done are not at all clear. One approach that is, IMHO, undervalued is the principal component analysis of morphological rather than genetic characters. That is, you measure things about (many) chimps, people and ourang outangs. A statistical technique shows you which of these matter, and how much of the internal variation they capture. It then combines these important measures into dimensions, ways of varying which combine important traits in exclusive ways. One about the primates might combine arm and leg lengths, body weight and chest width. Another might combine hairiness, mouth width and toe grip strength. These two dimensions create a 'space', a rectangle, on which each individual animal can be plotted as a point. If the analysis is done correctly, all the chimps cluster around one part of this space, the ourangs in another and the humans in a third. Individuals who overlap these clusters are indeed odd. If you do this with plants, you frequently find that they do not cluster in the same way, but rather form extended smudges. Their "phenotype", the way the genes turn into a physical object, is much more subject to variation, either intrinsically or because their growth has been disturbed by e.g. grazing. Looking out of my window I can see nettles that vary from one inch high mats to would-be shrubs. Consequently, taxonomists have tried to identify characters which do not vary so much, often associated with the flower, or things which are diagnostic of what they see as a divide in the 'smudge', such as having hairs on the stem or not having them. However, this plays straight into the hands of the splitters, for if you find a sub-population that has these diagnostic hairs in some other way - let's say, as waxy scales - you can then set up a new species. My very amateur sense is that genetic analysis, a clear view of where an organism grows and how it goes about its business and, third, phenotypic principal component analysis will all need to come together if we are to end up with a taxonomy that is stable, that is useful and that is parsimonious. = We need to know that the family relationship between entities is reflected in their genes and therefore in their evolutionary history. = We also need to know whether the plants live together or are adapted to entirely separate ecological niches. Many Himalayan Callista group Dendrobiums would not be valid separate species, I suggest, if it were not for the fact that they are adapted to and grow in and entirely different circumstances. = Third, we need to know what physical manifestations of genes and environment - hairs, stripes - are truly diagnostic of difference. Notice that this hierarchy inverts what has happened in taxonomic history. That is, we looked for stripes and hairs, largely ignored ecology and inferred family relationships. Hence the re-zoning that is going on, and will I suspect continue for some time. ______________________________ Oliver Sparrow +44 (0)1628 823187 www.chforum.org _______________________________________________ the OrchidGuide Digest (OGD) [email protected] http://orchidguide.com/mailman/listinfo/orchids_orchidguide.com
