Plants of hybrid origen

Jim McKenney
Mon, 14 Jun 2010 12:09:39 PDT
Donnie, I'm not a practicing taxonomist, but until we hear from one, let me
hazard an answer. In fact, I've discussed this informally with taxonomists
in the past. 

The short answer for situations such as the one you described is that the
population in question is often treated as a species. The plant we call
Fritillaria eastwoodiae provides a good example. It varies throughout its
range, in some areas tending towards one purported parent, in other areas
tending towards the other purported parent. And it is widely regarded as a
"good" species.

But the situation is not always so simple. In southwestern Virginia, Lilium
grayi seems to be in a species-like relationship with local populations of
Lilium canadense. Elsewhere in its range, Lilium grayi grows in relative
isolation and seems relatively distinct. Lilium canadense in other parts of
its range is distinct. But there is an area where the two nominally
different species behave as a single species. Most taxonomists are reluctant
to combine the two species (although I’ve read that Asa Gray himself had
doubts that the lily named for him was specifically distinct). 

But there is more to the story. I don't think there is a simple answer to
this question, in part because it addresses directly points over which
taxonomists differ: what is the significance of hybrids, what are hybrids? 

One school of thought says that if fertile hybrids occur naturally, then
that in itself is evidence that the populations involved are in fact members
of the same species (i.e. they share the same gene pool). This school of
thought views interspecies hybrids with skepticism; it takes the point of
view that if two populations with different species names interbreed, then
the taxonomy is bad; they are not different species, they are one and the
same species, however variable or different in appearance they seem. This is
the team I'm on. 

The contrasting point of view accepts the existence of interspecies hybrids
as entities nominally distinct from either parent. In the case of plants of
cultivated origin (garden hybrids), these entities are apt to be named as
nothospecies (with the name preceded by the times sign, ×). Wild populations
of “hybrids” are typically not given nothospecific designation but are named
according to the usual rules for plant nomenclature. 

There are cases where horticultural and formal botanical procedures either
clash or seem mutually contradictory. For instance, in the old days,
hybridists sometimes named their hybrids with Latinized names. Botanists
seem to have one take on this, horticulturists seem to have another. The
botanists sometimes use these Latinized names as the formal botanical name
for all hybrids of similar parentage. Horticulturists tend to use the names
to identify the original clone of the hybrid (if in fact there was one
original clone). If, for instance, the original hybrid clone or strain was
yellow flowered, but subsequent hybridizing along the same lines produced
red or blue flowered plants, then the practice of formal botany to use the
same name for all of these is very confusing to horticulturists who
associate the name with one particular plant.   

Before leaving this topic, be aware that the word hybrid itself is used in
mutually contradictory senses. Many people use the term hybrid in the sense
of a cross between two nominally distinct species. 

The Latinized Greek term from which the word hybrid is derived seems to have
had the sense of “mongrel” as opposed to interspecies hybrid, and this is in
agreement with a broader sense of the meaning of the word hybrid which is
just as prevalent as the interspecies concept: that hybrids are what result
when two different breeding lines (of the same species) cross. Corn, for
instance, is generally regarded as a single species, yet most corn grown
today is of hybrid origin. The hybrids in question are sometimes
distinguished as F1 hybrids. To the Romans, people of mixed parentage were
hybrids. In this sense, the puppies from a Dachshund mother and Poodle
father are hybrids.   

A lot more could be said about all of this.    

Jim McKenney
Montgomery County, Maryland, USA, 39.03871º North, 77.09829º West, USDA zone
My Virtual Maryland Garden
Webmaster Potomac Valley Chapter, NARGS 
Editor PVC Bulletin 
Webmaster Potomac Lily Society

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