New article on Lithops genetic differentiation, Kellner et a

[Mawa]

New to me anyways. Probably this is old news for some, but I would be delighted to see what others think.

Kellner, A. et al.: Genetic differentiation in the genus Lithops L. (Ruschioideae, Aizoaceae) reveals a high level of convergent evolution and reflects geographic distribution; Plant Biology 13 (2011) 368–380.

Some conclusions:

-Geographic distribution reflects genetic differentiation.
-Flower color does not matter.
-The number of seed capsule locules does not matter.
-Windows don't matter, neither does morphology in general.
-Dinteranthus vanzilii is really close to Lithops.

What do you think, iann and others?

[Pete A]

They looked at the chloroplast DNA and discovered that there was little sequence variation in the investigated chloroplast markers. To quote the paper: By applying a probability limit of 80%, only 10% of the species could be correctly assigned. It's a first step but much more work is needed so I suggest not taking their results as the final answer.

Jonathan Clark (of the Lithops key) is writing a review of the paper for the BCSS journal.

[iann]

The article is about 18 months old and shows some results from work going back nearly a decade. Previous results have only been shown as poster displays at conferences so far as I know.

The article presents results from chloroplast DNA, nuclear DNA, and AFLP sequencing. Because of the limited resolution of standard DNA sequencing for mesembs, the group has been focussing on the use of AFLP. Most of the results in the paper stem from this, although the other DNA results are also shown. One huge caveat with this work is that it was done using plants that have been cultivated in a single collection for a number of generations. This may explain some of the odd data thrown up, such as an occasional plants appearing in different clades from others of the same species, or that may simply be down to the limited statistical reliability.

The results do not offer much information about species delimitation (somewhat inevitably given the source of material), but suggest that the widely accepted intra- and inter- species relationships within Lithops are not supported by the genetics. The clades found contain a mix of yellow and white flowered species, as well as mixtures of species from completely disjunct geographical regions. Not that it is entirely strange mixtures, with many of the expected close relationships also shown. There is also the suggestion that some subspecies, for example from L. karasmontana, do not correctly belong within the same species. Results from this and previous work further suggest that Lithops is paraphyletic wrt Dinteranthus and possibly others.

All that is from memory, so apologies if some of the information is slightly wrong. I have read the paper but don't have a copy of my own. The results are intriguing and quite plausible. I have been doing breeding experiments this year to test some of the more unusual suggested relationships. A successful cross between a yellow flowered species and a white flowered species is very unusual, and if the few random attempts I made produce seed then it would be strong support for that relationship.

[Lindsey]

Hi Ian
I wish someone would do genetic testing on L.steineckeana!

[iann]

Hi Ian
I wish someone would do genetic testing on L.steineckeana!

It wouldn't tell us anything we don't already know.

[mamuga]

I am not a botanist. I am a mathematician.

If someone changes my axioms it will come whole collapse.

Does that mean that someday I will have to change my lithops labels?

So. . . . Dinteranthus vanzilii is a lithops? . . . Or it is not a lithops?

The old question: to be or not to be.

[Marlon Machado]

Hi Iann,

I can send you the pdf of the article, just PM me your email address.

Cheers,

Marlon.

[iann]

Dinteranthus have traditionally been excluded from Lithops because of the complex capsules, tiny seed, lack of windows, and non-embedded growth habit. None of these things are really gamestoppers. There are already Lithops with capsules almost as complex as Dinteranthus, a huge range of seed sizes almost down to Dinteranthus size, essentially window-less Lithops, and the embedded growth habit isn't something which would be considered a critical feature by most taxonomists.

One of the difficulties of a phylogenetic approach to taxonomy is that something like Dinteranthus (or something even more extreme) can potentially arise from a particular Lithops and leave the rest of the genus paraphyletic. The alternatives are to include the highly developed oddball in the genus or split the genus into two or more pieces. In the case of Lithops it is far too early to do either, but it certainly looks like some changes would be needed to create a monophyletic genus. I forget the details of exactly where the Dinteranthus species sat within Lithops but I seem to remember them forming a tight group except for D. vanzylii which sat elsewhere.