I've typically seen the trifoliate types listed as Poncirus. I have also recently noticed it listed as Citrus trifoliata on this site. It this the new accepted genus name?
http://users.kymp.net/citruspages/trifoliates.html

Cheers, Barrie.

Its Poncirus Trifoliata. Flying Dragon is listed as being a cultivar of Poncirus Trifoliata but some list it as Poncirus Trifoliata var. monstrosa.

The Poncirus is now considered as a Citrus by scientists.
Like Australian Microcitrus.

So there's two schools of thought, scientific and personal.

Cheers, Barrie.

Not all scientist go along with Poncirus being classified in the genus Citrus, many taxonomist have not accepted the change. The jury is still out on this. - Millet (1066-)

There are two varieties of taxonomist --lumpers and splitters.

This should not be a question of belief but one of genetics. How close is Poncirus to Mandarin or Papeda? Or to Eremocitrus etc. ?
Fact is that P. can be crossed with any other true citrus. But what doese that mean? Apple can be crossed with pear and quince. Are they of the same genus?
/Robert

How far does the cross breeding ability go in the Rutaceae family?

If one uses the ability to cross concept, then the orchid family would only have 3 or 4 genera -- a nightmare.

I believe most (all?) Florida citrus scientists will keep Poncirus separate. It certainly merits separate genus status by a number of qualities -- deciduousness, compound leaves, physiological differences (cold hardiness), different flower structure, oil glands inside the fruit (as opposed to just on the surface). I think the DNA folks are going a bit off the deep end with their revisions -- remember, we share something like 90% of our DNA with mice.

We must also remember that taxonomy is a human endeavor, created by humans for human convenience. The plants don't know and don't care what genus they belong to -- it's totally a matter of human convenience. And in that case, I think it important that Poncirus be kept separate from Citrus. Yes, the DNA shows us that they're quite close. But they are too obviously different to say they are the same.

Adapting what Dr. Manners says about DNA closeness, if applied to the Chimpanzee and Humans (96 percent the same), some taxonomists could make the case that both Chimps and humans were in the same genus. - Millet (1,065-)

Guolu Liang, Guangming Xiong, Qigao Guo, Qiao He and Xiaolin Li. 2007. AFLP Analysis and the Taxonomy of Citrus. Proc. XXVII IHC-S1 Plant Genetic Resources. Ed. in Chief: K. E. Hummer. Acta Hort. 760:137-142.

This paper compares many species of Citrus, Fortunella, and Poncirus using amplified fragment length polymorphism (AFLP). In their study, Poncirus clustered as quite different from Citrus, except for C. Hystrix, which seems closer to Poncirus than to other citrus.

So while they don't redefine the genus Citrus, they do seem to consider Poncirus to be clearly different, and they make no suggestion that it should be included in a lumped genus Citrus.

I read that there was a common ancestor of all Citrus about 7 mio years ago. The question for me is: does this statement include Poncirus?
/Robert