Question re species or sub species.

[bil]

OK. I read somewhere (probably the Big Boys' Book of Useless Facts) that the plant on the planet with the most species is grass, closely followed by orchids.

I also see a huge number of species of orchid that will hybridise (and presumably produce fertile offspring).

Now, the technical definition of a species, as destinct from another is that two seperate species cannnot produce fertile offspring.

If we stuck to that strictly, how many true species of orchids would there be?

[Brooke]

When you talk about sub-species do you mean hybrids. They do occasionally find a new species but a species is a species but if bred to another species they become primary hybrids.

You can't breed two different species if they aren't in the same "family".

Or am I totally not understanding your question?

[naoki]

Bil, there are many different kinds of species concept. "species" is a concept which is made up by human for our convenience any way. So depending on the topic of your interest (taxonomy, conservation, evolutionary biology, virology etc), biologists use the relevant types of species concept to discuss the topic.

Considering reproductively isolated groups as different species is a convenient concept in animals, but not in plants. For example, there are some species with various ploidy. A single species could contain diploid (2x), tetraploid (4x), hexaploid (6x) individuals etc. There could be (but not necessarily) reduced gene flow between the different ploidy, but they are considered to be a single species (in sense that they share the evolutionary fate). Evolutionary path of plants had lots of intermixing, and it is one of main features of plant evolution. Also evolution through hybridization is not unique to orchids and occurs in majority of plants.

Orchids went through explosive divergence recently, so lots of species are relatively new. That's a part of the reasons why orchids seem to have less reproductive isolation.

Also, grass family (Poaceae) isn't the most diverse family in plant kingdom. You can look at this:
https://en.wikipedia.org/wiki/Flower...lant_diversity

Composite family (dandelions etc) is the most specious at this point, and then Orchid family.

[Subrosa]

"Taxonomy is the diaper used to package the mess of evolution into discrete packages". What differentiates a species depends upon the species. By the definition of being able to produce fertile offspring, there are considerably fewer, perhaps even only one species in the genus Xiphophorus. This will come as a surprise to the describers of quite a few species. As a matter of fact most Swordtails, Platys, and Variatus available in the trade are hybrids of multiple species. Pure species are most commonly passed between hobbyists. Differences in skin color and pattern, along with skeletal differences in North American ratsnakes (many of which hybridize readily in intergrade areas producing fertile young) warrants species distinction. However there is sufficient overlap between some species so that without knowing where a skeleton was collected a positive species id based solely upon the skeleton may not be possible. This same standard applied to human beings would likely result in our being split into multiple species or subspecies along racial lines, as any forensic pathologist can determine fairly reliably the the race of a person by careful examination of the skeleton.

[plantbuddy]

As Naoki said, the non-fertile offspring concept of a species is only applicable to animals. Such as the horse + donkey = sterile mule.

In plants, taxonomists argue and re-define species endlessly, some are called lumpers, and lump many species into one, and others splitters, who sub-divide existing taxa into smaller units (and therefore often get to name them).

The appellation of sub-species only applies to non-cultivated plants, as it is part of the botanical classification regime ( International Code of Botanical Nomenclature) ie. the botanical latin names; Genus, sub-genus, species, sub-species, variety, sub-variety, form, subform, (if I recall correctly).

Cultivated plants are named according to the ICBNCP (International Code of Botanical Nomenclature of Cultivated Plants). Thus the grex names, hybrid cross names and hybrid name registration.

[PaphMadMan]

Using hybridizing ability as part of the definition of the species concept isn't something any serious biologist would do as a general principle. Species is defined in different ways for different groups of organisms. Hybridizing ability doesn't come close to working in general even for animals. Genus Canis (wolves, coyotes, dogs) would all be a single species, domestic cattle and bison would be the same species, lions and tigers and leopards would all be the same species, the live-bearing fish in Genus Xiphophorus were already mentioned, and the list goes on and on and on.

Among orchids, most genera, many subtribes, and even some tribes might be reduced to a single species each. Genus Paphiopedilum, one species? Laeliinae subtribe, one species? If Cattleya labiata, Epidendrum radicans and Prosthechea cochleata would be considered the same species, obviously the species concept would be pointless. There would be perhaps a few dozen species of orchids in all. The grasses wouldn't fare that much better as there are plenty of hybrids there too, including intergenerics.

It is worth remembering that species is a concept we find convenient and try to impose on the natural world. The natural world is not obligated to comply, no matter what the definition.