A new botanical classification system ??



> Forwarded message re classification I thought might interest you - has
> anybody heard about this

Connie Hoy

>
>
>   ------- Forwarded message follows -------
> Very interesting article in today's Independent:-
>
> A rose is still a rose, but everything else in botany is turned on its
> head
>
> By Michael McCarthy, Environment Correspondent
>
> It began seven years ago, when scientists at Kew Gardens started comparing
> the plants of the world through their DNA, their genetic blueprint, on a
> large scale for the first time. What they found will cause a botanical
> revolution.
>
> Comparison of individual genes showed that the relationships between plant
> families, which had hitherto been widely assumed, were in some cases
> wildly inaccurate; more than that, the most surprising kinships existed
> between the most unlikely flowers and trees.
>
> Gazing on the red blooms of the Asian lotus as they emerge from the still
> waters of a pool, for example, you are not immediately put in mind of
> Berkeley Square. But you might well be, Kew's molecular biologists have
> discovered.
>
> The huge flowers of Nelumbo nucifera, for thousands of years a sacred
> plant in India, China and Tibet, are not related to the waterlily family
> which they resemble, and with which botanists have long and naturally
> associated them. Their closest relative, it turns out, is Platanus hybrida
> - the familiar and hardy plane tree of London's squares, so common because
> until the Clean Air Act got rid of London's smog more than 40 years ago,
> they were the only things that would grow there. The sacred water flower
> of the East and the giant tree of Britain's capital are first cousins.
>
> In revealing many more such unusual relationships, the exploding science
> of genetics has made possible a complete - and now accurate -
> reclassification of all the families of the world's flowering plants and
> trees, which the scientists at Kew have led and which has just been
> completed. It represents for the first time an evolutionary tree of plants
> which is certain to be accurate.
>
> It has been based on comparing their DNA, their genetic code, rather than
> their morphology - their appearance and physical characteristics, which is
> all that plant taxonomists have hitherto had available to them.
>
> People have been classifying plants since prehistorical times, of course:
> which ones provided food, which were poisonous, which were medicinal.
>
> Medieval herbalists made bigger classifications, but it was not until the
> Age of Enlightenment at the end of the 18th century that a complete and
> systematic classification of plant families was first attempted, by the
> Swedish Naturalist Carl von Linne, known as Linnaeus.
>
> His classification was considerably improved by 19th- century French
> botanists, such as Decandolle and Jussieu, who established the families
> with which we are now familiar, such as the compositae, the daisy family,
> the brassicae, the cabbages or mustards, the rosaceae, the rose family,
> and the orchidaceae, the orchids.
>
> Twentieth century botanists have continually refined these
> classifications. The trouble has been, says Dr Mark Chase, the man who has
> led the Kew DNA team, that no two of them have been exactly the same.
>
> "There have been three major classifications of the world's plants in the
> last 20 years and each of them has had different ideas, not only between
> each other, but between different versions of the same classification," he
> said.
>
> For example, in 1981, the American Arthur Cronquist divided all plants
> into 321 families; the next year, his fellow American Robert Thorne
> divided them into 440 families; and in 1997, the Russian Armen Takhtajan
> divided all plants into 598 families.
>
> "These men were trying to assess the plants' genetic information from what
> they could see with the naked eye," Dr Chase said. But he and his fellow
> scientists from Kew and from around the world have now done something new:
> they have gone to the genetic information directly.
>
> New techniques of molecular biology that became available in the past
> decade have allowed them to sequence, or identify, individual genes in
> plants' DNA and then assess them for similarities across species.
>
> They have done this with three genes for each of 565 plants representing
> all the world's flowering plant families, the first and most important
> being the gene responsible for rubisco, the enzyme that controls
> photosynthesis, the essential process by which plants convert sunlight
> into energy.
>
> The relationships between plant families indicated by the rubisco gene has
> been exactly repeated with the next two genes, convincing Dr Chase and his
> colleagues that at last, 200 years after Linnaeus, they have the true
> picture of how all the world's plants are related.
>
> They now class them in 464 families. Botanists will have to rewrite their
> floras as a result. Not only is the lotus related to the plane tree rather
> than the water lily. Roses are not related to saxifrages or the bean
> family, as had been thought, but to the buckthorns, the nettles and the
> figs. Orchids are not related to lillies, as once thought, but to the
> yellow star-grasses.
>
> So from next month, when the new classification is published, a rose will
> still be a rose; but much else in the plant kingdom will be very
> different.
>
> Family Trees
>
> It was an 18th-century Swedish botanist who first developed a scientific
> system for classifying all plants, and subsequently all living things.
>
> Linnaeus was born in 1707 as Carl von Linne, the son of a country curate,
> and was obsessed with flowers from the age of eight. As a research student
> at the University of Uppsala in 1730 he realised that the scientific
> arrangement of plant species was inadequate, and began to sketch out his
> own.
>
> Linnaeus invented binomial nomenclature - the system of using two Latin
> names to describe plants and animals, the first describing the genus, or
> related group, and the second the species itself.
>
> Thus herb robert, the common pink flower of English woodlands, is
> (Geranium robertianu : it is a member of the Geranium genus, like many
> others, but robertyianum describes this particular one. This naming system
> is now in universal use for all living organisms.
>
> The criterion of classification Linnaeus used for plants has been
> superseded. He classified them according to their sexual parts, such at
> the stamens or anthers (the male parts), and how many each had: a plant
> with five anthers would be in the pentandriae. The modern division of the
> plant kingdom into large related families, such as the cabbages
> (brassicae) or the daisy family (compositae) is a product of 19th-century
> botanists.
>
> The new classification supersedes both: it divides the plant world into
> families, but for the first time does it with precision.
>
> Independent
>
> Stand by for major renaming over the next few years!
> It also raises some intriguing horticultural possibilities - sacred lotus
> grafted onto plane trees ????
>
> David Roberts-Jones, Heald Green, Cheshire
> d*@cix.co.uk
> Apologies for the long post, but thought this might be of interest to many
>
> --



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