From: "NAME \"Wilbert Hetterscheid\"" <W.HETTER at pbga.agro.nl> on 1997.01.08 at 00:06:54(57)
Aroidellers and advisors:
I hope this taxonomy thread is still endurable to you all. If
not, I am sure the moderators will throw us out. Until that
point is reached there are some points to be made regarding
John Grimshaws and Darth Vaders points of view.
The emphasis on similarities rather than differences in asses-
sing phylogenetic relationships is nothing like a personal
choice! It has been proven beyond any doubt in many papers,
that to estimate phylogennies ONLY shared similarities are
evidence. John mistakes the act of differentiating species
from one another by using differences from estimating phyloge-
nies. Indeed delimiting species, the so called "terminal taxa"
of most phylogenies is a matter of weighing differences AND
similarities but the final grouping of those species in phylo-
genetic meaningful groups (higher taxa) is done solely by
estimating shared similarities. Differences play NO role in
this segment of taxonomy. There is no law either that states
when and when not a group of organisms should be selected for
individual recognition by assigning it to a Linnean category
and giving it a name accordingly. Once the phylogeny has been
reconstructed (like as in the original graphs presented by me)
it is up to the taxonomist to cut up that graph in units that
he wants to give a rank and a name. In the case of the
Sauromatum/Typhonium graph that Peter and I reconstructed, the
choice to maintain Sauromatum as a genus is still open. When
we would decide to maintain Sauromatum, we would have to
redefine Typhonium AND create a new genus alongside it and
Sauromatum. This particular choice COULD be based on differen-
ces indeed, as John rightfully claims. One could argue that
Sauromatum looks "so peculiar" that it needs a separate status
as genus. This "so peculiar" is nothing else but the statement
"It differs SO much from all other related genera, it should
stay". However we have learned during the last decades that it
is better to try and avoid idiosyncrasies as much as possible.
The interpretation of the morphology of a certain plant in
terms of categorical assignment (e.g. is this a genus or a
number of genera in a subfamily?) is totally subjective and
has no basis in evolutionary thinking. Therefore we propose to
make a choice of genera based on phylogeny alone. Stability of
names is a second argument that may be used subsidiary to the
primary choice. Therefore we think that reflecting the correct
phylogeny of S. venosum and S. brevipes is best served by
identifying them as part of the evolutionary closed unit
called Typhonium. The alternative would mean the creation of a
new genus of Araceaa that accomodates a number of former
Typhoniums. The net result, three genera, does not reflect the
phylogenetic relationships between all species in this study.
The fact that two are in Sauromatum, several in Tyhonium and
several in Grimshawia is uninformative as to their mutual
relationships.
I agree with Johns paragraph on the conservation but I, as
many of you, also have a bit of a disappointed feeling that
such a well-known name like Sauromatum should fall. There are
however taxonomists today that advocate to maintain such well
known generic names even when the correct phylogeny tells
another story. It has been called "The New Phyletics" (Todd
Stuessy being the founder of it) and I have seen it proposed
in a recent revision of Begonia groups in Africa. Alas, I am
not yet convinced that we should do this but there's always
room for reconsidering stances.
To Darth Vader: Darthy baby, let's see what I can say about
your background grumble. I don't think that I had to expose
all the data that have lead to the cladogram I showed in my
first message. That is beside the point. The idea was to
illustrate a reason to sink Sauromatum. As I said, fellow
taxonomists will judge the value of the data used and the
methodology. Your problem with CLADISTS (what the hell are
"cladisticians"????) is outdated I am afraid. The discussion
about the bad manners of many prime-time cladists has long
subsided and a new generation is working on the details of the
methodology. The days that they fought like cats and dogs in a
less than subtle manner are over. The cladistic revolution has
had profound and positive influence on systematic thinking in
general. It has showed us that a method used to reconstruct
something needs a basic philosophy that clarifies that the
method can reach such a conclusion at all. Cladistic philosop-
hy started out by showing that until the 19sixtees, the phi-
losophy of taxonomy had many faulty logic (if at all!) in it.
Cladistics (now called Phylogenetic Systematics) has brought
up a whole new generation of systematists with the notion that
authoritarianism in taxonomy has yielded NOTHING that lasts
for science to use in evolutionary reconstruction. We had to
start all over again and we did. The result is a period of
great instability in classifications that will certainly last
many years to come. But I'd sooner blame the oldies for that
than the cladists.
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As to phenetics the case is simple: had they maintained that
their method of data analysis yields purely statistical outco-
mes about overall similarity between compared entities, then
nothing would have gone wrong for them. Alas, some prophets
started to feel that the contribution of phenetics to biologi-
cal science would be very limited indeed and started to murmur
that there WAS something "phylogenetic" about their outcomes.
Rightfully so, they lost the debate over this issue, since
they were usinfg wrong logic. Cladists got an easy victory
there but that wasn't their fault.
Phenetic analysis will be a good tool in the analysis of data
in a non-evolutionary field, like the classification of unna-
tural biodiversity as found in cultivated plants.
I get suspicious when people introduce the term "religion".
That term is often used by bystanders who do not fathom the
details of the discussions and all too easily translate fana-
tic adherence to a scientific system as "religion". It also
seems to place them "above" the debate, which I find a trifle
irritating. In religious suroundings a doubters' head comes
off without discussion, in science ones head comes off AFTER
discussion. A very essential difference.
I appreciate the cladistic way of reconstructing phylogenies
because its basic logic is so simple and has proven to
withstand all critique. There IS no better way of reconstruc-
ting phylogenies at this moment. And even when a better system
will be devised in the future, I am sure that cladistics will
be the basis! The latter sentence may be looked upon as
"belief", I grant you that.
Obee Wan Kenobee
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