Divergence: how close do they have to be?

[LJA]

Sue,

How "different" in terms of genera can two parents be before a cross just won't "take?" (Or, if it does take, will yield progeny that are sterile?) Do you have any idea? Would it make any sense to even try crossing a Cattleya with, say, an Angraecum?

Thanks...

[Sue]

Grrr.

I guess I'd better do a FAQ entry on Phylogeny.

The answer I will give will be complicated, specific (no pun), and contentious. But I need to put together a little diagram first.

I will get back to you later today or tomorrow.

[Sue]

Well, here's a short answer:

Some sections of the same genera cannot interbreed. This is especially likely in very large genera, such as Dendrobium and Oncidium.

Alternately, plants have been bred which are in different tribes. Which is perhaps just a sign that the taxonomy is wrong, or at least misleading with regard to the phylogeny.

For perspective, this is the grouping of family Orchidaceae:
Family>Subfamily>Tribe>Subtribe>Alliance>Genus>Sec tion>Species

So plants will always interbreed within a species. Some different sections among some Genera will not interbreed. So that's an incompatability on the first level up from species. Alternately, some will breed into a different tribe. So that's an incompatability (presumably) on the Subfamily level; the 6th level up from species. So that's an absurd amount of variation.

There are some groups which are closer to others, and there are certainly patterns to be laid out.

Details will be here soon.

[LJA]

Awesome, thanks. These are questions I've had in the back of my mind but can never remember when I'm around someone who might know the answer. Look forward to it!

[amaximia]

The rule of thumb is, same family will cross easily. Same subtribe may cross but with more difficulty. Same tribe may cross but very rarely. Different tribes will almost never cross. It is impossible to cross a monopodial (i.e., Phal) with a sympodial (i.e., Cattleya).

Having said that, many dendrobiums will not cross with eachother like Sue said and cymbidiums have been known to cross with species from the Bletiinae subtribe. I believe the taxonomists are wrong in a few of the classifications.

Incidentally, I have Oncidium chromosome counts from a couple of different sources (Withner, Arditti) and they are all over the place! Some serious misclassification going on there apparently.

[LJA]

Thank you, amaximia. That answers it as far as I'm concerned. Glad you're here!

[Sue]

Hey Alex! Glad you came over to play!

I was going to put together a FAQ entry on breeding distant cousins. Do you mind if I use your post in the FAQ (with credit of course)? You put it very well.

– Sue.

By the way, Alex, if you'd be interested in writing a FAQ entry or two, your help would be more than welcome.

[amaximia]

Sue,

My pleasure. Although I'm not sure what to write about. Any suggestions?

[Sue]

Hmm. I don't know; anything would be helpful.

I was intending to write a FAQ entry on Ploidy right after the one on this divergence issue. You're welcome to take that one, if you feel like it.

I guess we also need some sort of 'how does flasking work' FAQ entry.

Hey; have you tried any crosses lately? I haven't in a little while, but I've got a few Pleurothallidinae opening in the next couple of weeks. I'll be posting about that, with pictures, when that happens.

At any rate, if you've been doing any evil genius stuff, you should let us all know about it. Or at least post some pictures from your recent trip.

– Sue.

[Sue]

My complete answer to this question, with Alex's help, is now on the FAQ thread; entry #3.