What is an alliance?

[tropterrarium]

Can someone clue me in on the definition of an alliance? Although it is used in the name of many Forum groups, the glossary of Orchidboard does not contain an entry for it! Google? no luck. Wikipedia: nothing. Rather strange.

From what I gather, it is not a formal rank in botanical taxonomy (though Wikipedia implies it a bit). It would be above genus and below subfamily. Supergenus, infrasubfamily?

I only found here (not a terribly reliable source, I fully realize) that "The term Alliance is used to describe a group of genera that have many common characteristics and can be used for cross breeding." So, is it just a horticulturist term with no botanical/scientific underpinnings? Popular grades (as opposed to clades), maybe?

Does that then mean that not all genera are assigned to an alliance? Are alliances just for the favorites amongst collectors and hybrid breeders? Just received the The Marie Selby Botanical Gardens Illustrated Dictionary of Orchid Genera and read through the intro. No word of "alliances", which supports that angle.

Any illumination of the topic would be great. Thanks!

[RosieC]

An alliance is a grouping of orchid Genuses. It can be looked at the oposite way arround as well, it's a way of dividing the orchid family down into smaller sections.

However people often use the word for a grouping which is not in the strict sence an official alliance group. This is generally when it seems natural to most people to group certain genuses together.

The taxonomy of Orchids generally has the following levels...

Family (that's Orchidaceae or Orchid)
Subfamily (there are 5 of these within Orchids)
Tribe
Subtribe
Alliance
Genus
Subgenus
Section
Species/Hybrid

Not all orchids will bother with all levels, for example if there is only a few orchids in a genus there is no need for subgenus and section, a large genus like Phalaenopsis has these sub-groupings though.

Generally an Alliance groups together similar genuses inside the larger tribes/subtribes. I find that many times what people call an Alliance is actually one of the smaller tribes or subtribes. Or even a sub-section of that.

For example here on OB I have noticed that we have a 'Vanda Alliance' which includes Trichoglottis, but more strictly the Trichoglottis is part of the Vanda tribe but is not part of the Vanda alliance (it has it's own alliance called Trichoglottis). At the same time Phalaenopsis is part of the Vanda tribe, but we have listed that alliance seperatly.

That happens simply due to how much we talk about certain orchids. Trichoglottis gets talked about less and so there is not much point seperating it to it's own alliance section.

At least... what I have said above is true based on one set of taxonomy, but taxonomy is fluid and things keep moving from one grouping to another as new research occurs.

This Wikki page may either help, or confuse you more. However note that this is mostly based on the work of Dressler and as said above folks are constantly re-clasifying orchids and moving them about the structure so while it may give you an idea, it could easily be out of date in many places.

Taxonomy of the Orchidaceae - Wikipedia, the free encyclopedia

[Tindomul]

I never considered this question. I really think alliances are a horticultural division. Botanically speaking it is better to group the orchid genera by subfamily (Cypripedioideae, Spiranthoideae, Epidendroideae etc...) and then by tribes ( Diurideae, Diseae, Epidendreae, Vandeae, Vanilleae etc...)
Then there are subtribes, and sections, etc..

Also, found a reference for you.
R.L. Dressler (1993) Phylogeny and Classification of the Orchid Family

[susiep]

Thanks, Rosie! That was actually very helpful.

[tropterrarium]

Hi Rosie,

that helps a bit. Is Alliance an ICBN sanctioned rank? from Taxonomic rank - Wikipedia, the free encyclopedia it does not look like it. Specifically "If names were "intended as names of orders, but published with their rank denoted by a term such as": "cohors" [Latin for "cohort"[4]], "nixus", "alliance", or "Reihe" instead of "order" (Article 17.2), they are treated as names of orders."

Notice that alliance = order, so ABOVE family!

The informal nature of alliance also seems to be supported by having the same name as the main genus, including same ending. Subgenera are in parentheses, and (sub)tribes, (sub)families etc. have different endings/suffixes: -ina, - aea, -oideae, -aceae.

And some subtribes with multiple genera do not have an alliance. Many alliances also seem to contain but a single genus, so serious oversplitting, IMHO. It is particularly noticeable among Tribe Cymbidieae, also happens to be a group of prime horticultural interest.

The wikipedia page is very helpful, printed it out.

Timodul: looking into getting Dressler.

P.S. Plural of Genus is genera, not "genuses"

[Tindomul]

alliance cannot equal order. All orchids are in one family Orchidaceae. Alliance has to be lower in rank than family, not higher. The order they are in is Asparagales which includes other plant families.

[RosieC]

I've no idea if it's ICBN sanctioned. I've only really come across it here and in that link above.

As I understand it Dressler is one of the main references for all this stuff in Orchids so it's worth taking a look at his book.

[Connie Star]

It would be fascinating to do DNA studies of orchids to classify them. Tindo?

[Tindomul]

Most taxonomy today uses dna evidence to help organize plant species. I don't know how far they have gotten with orchids, but they have Masdies, and Phals pretty much sorted out. I'm sure they have most of the family sorted out also.

[calvin_orchidL]

Rosie,

Excellent definitions and explanation. I'm no taxonomist, but I've always been mildly miffed that phals and neos got their own section of the forum, despite being merely little alliances under the aeridinae subtribe (which includes vandas, and basically everything else vandaceous). On the other hand, the other two major subtribes angraecinae and aerangidinae were lumped in with all the other vandaceous genera, which aren't even in the same subtribe.

With that said, I'm heavily biased, and I understand that on a forum like this, it's much more useful to group sections by their relative popularity