"the DNA sequence of the organism IS the organism "
Isn't this like saying that the detailed blueprints for a motorcycle IS the
motorcycle? Or that the word "sun" IS the sun? An organism has DNA, and
requires DNA at all stages of life, but the two are not the same.
A single DNA sample of a given species is often regarded as sufficient for
molecular investigations. Yet how can a solitary specimen be regarded as
sufficiently representative of a species? Such a specimen cannot hold
information about infraspecific diversity, either within or between
populations; it also may not be representative of that species in various
ways. By contrast, the taxonomist is often able to consult multiple or many
specimens for a given species, from different localities and likely
exhibiting variation. This difference highlights differences in the goals
of these disciplines.
There is much debate about whether species exist in a traditional
sense. Taxonomy-- no matter the status or fashion of "species"-- is
maintained so that we can communicate with each other about plants. In
everyday life this is an essential tool. Scientific plant names do, by and
large, conform to unique and recognizable (morphological) character states,
to discrete species in nature. Taxonomic classification need not strive to
reflect the latest (and ever-changing) insights of molecular work. They are
not absolute parallels. Boundaries between species or genera may be fuzzy.
Taxonomy is practical, or applied, while most of the other subjects being
discussed here are theoretical. This is a critical distinction.
I wonder how many of these phylogenies and cladograms, which represent
wonderful insights to be sure, will be dog-eared treasures 50 or 100 years
from now. There are many, many classical monographs, revisions and floras
that are held in such regard today. Unfortunately, modern funding is
directed to molecular science, almost to the exclusion of revisionary and
floristic work. Few people are served by a cladogram elucidating the
phylogeny of the Rosaceae, while a revision of Ficus or Haemanthus will be
of use to foresters, horticulturists, law makers, naturalitsts and others
for decades.
Dylan Hannon
On 31 October 2012 15:19, Christian Lachaud <christian.lachaud@gmail.com>wrote:
> Sir, I'm sorry but I don't understand your statement, although getting a
> vague idea of the global picture ("This leads me to feel that there is
> probably no such thing as a "species" but rather many ways of viewing the
> biological world.").
> You seem to disagree with the way living forms are categorized, and maybe
> are you correct if defining the tool for this categorization is an
> impossible challenge.
>
> But if there is no species, there must be another concept representing
> stable (yet evolving) forms of living beings.
>
> What would be your suggestion? Dynamic systems? How would categories be
> defined?
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