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Hybrids, grexes (greges), nature, evolution, human interest and

  • To: Multiple recipients of list AROID-L <aroid-l@mobot.org>
  • Subject: Hybrids, grexes (greges), nature, evolution, human interest and
  • From: "Wilbert Hetterscheid" <hetter@worldonline.nl>
  • Date: Sat, 29 Apr 2000 13:04:42 -0500 (CDT)


Peoples of aroid-l and Arisaema-l,

Since there has been some cross-posting on the subjects in the header above,
I forward this message to both lists. It's gonna be a longer one and not for
the romantic souls among us, so there you have two reasons to delete this
message right now..........

You're still reading this? O.k., suit yourself...................

The main players in the discussion are Bonaventure Magrys
(Aroid-l/Arisaema-l), Neil Carroll (Aroid-l), Bjoern Malkmus (Aroid-l), Mark
Burack (Aroid-l) and Eduardo Goncalves (Aroid-l). The main themes that I'd
like to address here shortly are the differences between nature's way of
hybridising species and the human way, the naming of artificial hybrids and
why humans hybdridise plants (here's your last chance to NOT get involved.
RETURN NOW, while you still can............!!).

1) naming hybrids: Bonaventure (may I refer to you as BM from here? Thanks)
introduces the grex-naming system as in place for orchids, as a means of
documenting Amorphophallus hybrids (or any hybrid, I suppose). As co-author
of the International Code for Nomenclature of Cultivated Plant (ICNCP), I
can tell you all that the grex system has been under fire for a few years
now, resulting in deferring that system to a mere note(#4) to art. 4,
dealing with cultivar-groups. The problem of the grex is that its
information content is limited. BM's explanation in his message to aroid-l
(27 April) perfectly illustrates this. You need a LOT of extra background
information to interpret e.g. his example grex Amorphophallus Bloody Giant.
Since it represents a collection of seedlings, which individually may
undergo different fates (clonal perpetuation, recognition at the cultivar
level, or die), it actually tells us nothing of great relevance. It merely
tells us, WHEN its history is recorded at all, that entity A and entity B
have been
crossed (in one particular order) and produced offspring. Nothing more,
nothing less. NO horticultural
characters of a grex are registered, not even in The RHS register (which IS
a grex NAME register and, unfortunately, NOT a cultivar register!!). This
system implies preciseness because names are created, but it indirectly
promotes an explosion of "names" of horticultural entities (grexes/greges)
of which the horticultural value is unknown. We, as members of the
commission preparing
the ICNCP, have often discussed why it has any relevance to put a name on
results of a mere intermediate stage in the breeding chain that should lead
to improved horticultural products, worthy of a really useful name (i.e. the
cultivar!!). A majority of the commission came to conclude that it has no
relevance to start naming such entities at an official level. Hence the grex
nomenclature is NOT part of ICNCP and is not supported by it. Nomenclatural
("taxonomic") focus should be on end-products (cultivars) because it is that
entity that by its definition (ICNCP, art. 2.2) is a stable entity. It is
the cultivar that bears a full description and can be qualified in terms of
horticultural value and can be preserved by designating a standard specimen
(all described in ICNCP). Neil Carroll (message to Aroid-l on April 29th)
describes the reasons for the focus on cultivars excellently. We are trying
to "improve our life" by creating plants that fit those demands better (more
beauty, better harvest yields, better tastes, etc., etc.). Cultivars that
have been named (mostly because they ARE an improvement), are registered in
cultivar-registers, either statutory (enforced by law) or non-statutory
(consensus of interested parties). Cultivars may be systematically grouped
into cultivar-groups (for the definition and content of which ICNCP has
issued a set of rules/definitions).

Thus, a cultivar name (as found on plant labels and in cultivar registers)
identifies a product of which characteristics are known and published (in
catalogues, research publications, taxonomic literature) whereas a grex name
merely says that A and B have been crossed. With the creation of a new grex
name with almost every new cross, the orchid register of the RHS is a giant
list (see also Sander's list of Orchid names = a grex encyclopedia of many
volumes) of crosses that have yielded offspring. Is that what we want to
know? I think it is a playground for people who like to give names to just
about everything they create in a nursery or their backyard, without
bothering about the question whether the result of their hybridisation hobby
has any merit beyond that nursery or backyard. Horticulturally important
products are usually the result of long breeding processes and the final
results that are introduced to society are only a small minority of all
resulting plants from the crosses that may have been done in the breeding
process. No serious breeder will want to register all these intermediate
crosses and put names on them, only to find that 99% of those crosses yield
inferior material.

I therefore would vote against the use of grex names in aroid "breeding"! I
advise the IAS as International Registration Authority for cultivated
aroids, not to succumb to this system. It will put a lot of extra work on
the registrar (Donna Atwood at Selby) and distracts from finding out what
are the properly introduced cultivars of aroids through the decades (a big
enough job as it is!).

In the end, as a horticultral taxonomist, I am of course NOT against
hybridising (Neil, don't worry!!) BUT I think that introducing the result of
hybridisation must go accompanied by a proper nomenclatural procedure, which
starts with thinking about the merit of introducing the hybrid in the first
place!! Bjoern Malkmus warns more generally against introducing new
Amorphophallus clones on the grounds that labels etc. get lost. That is
indeed a danger, and the longer the label is, the easier data get lost from
it, but I think that at some point when a particular genus of plants seems
to have horticultural potential, somebody will have to start introducing the
improved cultivars and they will have to be labelled. I think that would be
the proper way to do it because it will indicate that the introduced
cultivar is not the direct result of exclusively nature's actions but that
humans have interfered. That information is obviously relevant to some of
us. Those interested in buying a fine plant, will be able to communicate the
cultivar name to others and inspire them to ask for that cultivar in shops,
garden centers, and buy it. A good example is the recent introduction of a
clone of Pinellia, that may have developed spontaneously under cultivated
circumstances in a nursery as the result of a hybridisation between P.
tripartita (the purple form) and P. pedatisecta. The nursery was wise enough
to recognise it's potential merit and tageed it as a cultivar Pinellia
'Polly Spout'. Simple and effective. People will learn in the end what
'Polly Spout' looks like and they can then order it, knowing WHAT they may
expect to get. And THIS is the essence of effectively naming useful
cultivated plants. The grex cannot serve this purpose.

2) hybridising for the sake of taxonomy: this is a point that has to be
taken with great caution. Neil's example of the hybrid between Anth.
scherzerianum and wendlingeri having contributed to the idea that the latter
can be firmly placed in Sect. Porphyrochitonium, implies that species in
closer evolutionary proximity, should be easier to hybridise. This is
definitely not a general rule. It was so in the days when Mayr claimed that
the biological species (based on the Biological Species Concept) is a group
of individuals that may potentially interbreed with succes. This has
generally been promoted to mean that crossability in is an
indication of evolutionary relationships, not just between members of a
species, but also between species that are closely related. Shortly
thereafter, the discipline of "biosystematics" evolved rapidly, founded on
this notion. However, the discussion on species concepts has slowly
marginalised the biological species concept because crossability is just a
character of a set of plants, as is the posession of e.g. needle-like
leaves.

It is generally accepted that a speciation event may or may not lead to a
set of new species that can produce viable hybrids. This is brought about by
the fact that species in different plant genera show very different
behaviour in this respect. Orchids possess the proverbial promiscuity, even
to the point that species from different GENERA interbreed succesfully
("potentially", because in nature it may not happen at all, in greenhouses
it DOES!!). Orchids obviously have evolved a plethora of forms BUT they are
genetically far less progressive (that is the genetics of
breeding, which is a different thing from the genetics of morphological
change!!). Thus our ability to recognise species or higher taxa is obviously
NOT related to the interbreeding behaviour of those taxa! Therefore there is
no solid ground for evaluating evolutionary relationships between species or
higher taxa on the basis of potential interbreeding succes.

2) Now I am going to address a more fundamental point and that is the
parallell between evolutionary processes as going on in nature v.s. human
exploitation/copying of those processes. I have ended the above paragraph
with that distinction. Mark Burack asks if "undetermined" species may turn
out to be natural hybrids. Sure enough, when found in nature!!! Many
entities we cal "natural species" may have evolved through a chain of
processes of which hybridisation is one. Not to say, of course, that a
natural hybridisation always leads to a new species. In order for successful
hybridisation to occur "naturally" any or a combination of circumstances
must apply (proximity of different species geographically, coinciding
flowering times, compatibility of genome-parts dealing with developmental
success of embryos after pollination, correct pollination-vectors, correct
circumstances for hybrids to establish from seed etc.). For a species to
develop from this, the factor of duration/perpetuation is essential too. We
would not easily recognise a swarm of hybrids as a species when they appear
to be a mere ephemeral, very localised phenomenon. In fact, recognising that
a species is of hybrid origin is quite often done after the initial
publication/recognition of it at the species level.
In older days (when biosystematics reigned superior) we did it the other way
around, and recognised enormous numbers of species merely based on the idea
that hybridisation had occurred and that observed chromosome patterns,
indicating this, were tantamount to establishing species. These
"microspecies" e.g.
were recognised by the hundreds in a temperate Asteraceae genus as
Taraxacum. Luckily most of us have seen the "errors of our ways" and have
not perpetuated this line of recognising species this way, thereby accepting
that hybridisation as a means of speciation is o.k. but NOT the final story.
Eduardo says correctly that plants don't always tell us, and I say that that
doesn't matter at all. We recognise species even when we know nothing about
their origin.

How different are things with cultivated plants, of which we DO actually
know their origin (for the sake of argument I exclude ancient cultivars,
landraces etc., of which the history has not come down to us in written form
but of which we DO know they are "man-made"). Bjoern asks why we "improve"
plants at all when nature seems to be perfect to him. Well, Neill answered
that question perfectly correct. Whether nature is or is not perfect is an
evaluation of humans themselves and obviously we have decided that it is
not and there is a whole lot to improve. In fact we exploit nature to our
own goals but find that we also need to manipulate the natural products in
order to make them more to our liking. So we may start from accepting that
man-made
products, derived from "natural" products exist. And here lies a watershed
distinction between two worlds, the "natural" world where evolutionary
processes run in a number of ways and result in end-products
(species/populations/individuals) that make up the pattern we call
"biodiversity". Opposed to that is a grand
diversity of products brought about by man-made interference, whish does NOT
at all duplicate biodiversity as we percieve it in natural surroundings. Not
one Asteraceae taxonomist dealing with the genus Gerbera and revising it
taxonomically will describe for that genus all the morphological characters
he may have seen on Gerberas in a vase!! Nor will a Lactuca taxonomist
define that genus using the thousands of cultivars of lettuce as a basis for
describing the morphological diversity in that genus. In fact NO taxonomist
working on the revision of a genus of plants will include cultivars and
their characters in his work. He is working in an evolutionary context and
has a goal to publish with that paradigm in his mind. Apparently that does
not include man-made plant products (e.g. cultivars).

Obviously we DO perceive a difference between products of evolution as found
it in nature and manipulated man-made products
derived from the first group. In fact, we strive to differentiate them in
nomenclatural ways too. The first group (taxa, like genera, species,
families) are named using Linnean conventions described in the Botanical
Code, but to recognise the other set of end-results we use a different code
(ICNCP) that even tells us that we deal with a distinct entity, the
cultivar, which is NOT found in the Botancal Code. And although we may
indeed use processes or parts of processes as found in nature (hybridisation
as a prime one), we still feel that these processes yield different final
entities under cultivation (man-made) circumstances. We do not create
species in greenhouses, even though we may use "natural" processes!
Obviously we feel that what happens in nature and in greenhouses, although
superficially similar, IS essentially different.

I have written several papers with colleagues on this point because as
strange as this may seem, in history this obvious fact has seldom been given
recognition. In fact, this problem arises from the idea that man is part of
nature, hence what he does is, and what he creates is (Neil's point too in
his last message). Unfortunately, those saying this forget that man has a
unique feature, not found anywhere else in nature, and that is that he acts
with a pre-set goal. Although he may use hybridisation as a process to
create new things, he does that with purpose. If I wanted to create a red
Gerbera,
I could think of finding the fastest of most sucessful way of doing that and
start by crossing plant A with B because I think that particular combination
would be the best one for succes. Would an insect visiting Gerbera plants in
nature work that way? Would nature (or a player in nature, or a process)
think of putting plant A and B in proximity to create a red-flowering
offspring?
It is not inconceivable that at some short moment in time, nature would
accidentally create that red gerbera but then a plethora of circumstances
must be met for it to establish, whereas we, humans, would start
deliberately protecting that rare offspring, thereby increasing
exponentailly its chance to survive. Rightly so, because we WANT it to
survive! Could we say the same thing about nature? Would nature have its
"mind" set on preserving that red form? Guess not.

My conclusion: although we humans may be part of the natural context, we may
consider that some of our actions could be classified in different contexts,
even if we would like nature to be the all-embracing context in which we do
what we do. For purposes of human interest we already have created a
plethora of contexts in which we deal with objects and which we classify and
name especially for the purpose of that context. In our case, we have the
horticultural context, in which we try to establish methods, names, products
servant to the goal of the context: improving our surroundings/lives (see
earlier). I think that such a context needs its own labels and entities in
order to keep it from being confused with items in other contexts. Therefore
I think we must not look upon man-manipulated plants as the same things as
we find in the wild and logically therefore  NOT use the same classification
philosophy and nomenclature. Species names therefore are insufficient.
Species names are originally "devised" to indicate natural entities.
Linnaeus even excluded man-made plants from the species level (he made them
in "varieties" he often merely indicated by letters (alpha, beta)). Of
course, he sometimes did not recognise that a number of plants was not
God-made (his interpretation of the leading force of nature, not mine) and
gave them erroneously species binomials (e.g. Zea mays, Solanum tuberosum)
but we all know that was a mistake. These names perpetuate because we are
used to them
but no evolutionary scenario of the genus Solanum or Zea (should) includes
these.

In conclusion I am not saying that humans are "separate" from nature but we
must also accept that our actions have added a new kind of subclass of
contexts, in which pre-mindset things happen, something that nature had not
been confronted with until Homo sapiens came into being. Interesting is that
no
evolutionary scenario up to today, includes the existence of houses, cars,
railroads, cultivars, domesticated animals, even though each and everyone of
them has been "created" with the aid of "natural processes". They are all
separated from such scenarios because they are "man-made", and that is a
clean observation!!

3) Bernhard Strolka: at this moment a PhD student in Leiden (Netherlands) is
studying the genus Amorphophallus at the molecular level. He is putting
Amorphophalli, -uses, -us in the blender by the dozens....

Cheers,
Wilbert







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