Drosophyllum and cladistics

[CactusChris]

Not that I know much about it all but....

In Drosophyllum and a _few_ other like Byblis the plant's new leaves unroll in the opposite manner to Drosera and to most plants including ferns. This sets these plants aside - but does it make them more primitive or less? This could not have 'just' happened, but if it Drosophyllum is evolved from some 'drosera' ancestor then this change must have happened early on, and as a case of parallel evolution it happened again in byblis?? or did it happen just once? and cladistically therefore these two are closeley related?

BR

Chris

[Guest Aidan]

Chris - Here are some articles that at least in part discuss this subject. The last is perhaps the most relevant:

http://www.carnivorousplants.org/cpn/sampl...ence262Evol.htm

www.uvm.edu/~biology/Faculty/Gotelli/TREE16p623.pdf

http://www.amjbot.org/cgi/content/full/89/9/1503#F2

http://www.amjbot.org/cgi/content/full/90/1/123

A phylogenetic analysis based on the sequences of two plastid genes, rbcL and matK, indicated that Drosophyllum lusitanicum, a perennial subshrub native to the Iberian coastal fringe and northern Morocco (Juniper, Robins, and Joel, 1989 ), does not form a clade with other members of the Droseraceae, but is sister to the Dioncophyllaceae-Ancistrocladaceae clade (Fay et al., 1997 ; Meimberg et al., 2000 ). The exclusion of Drosophyllum is also supported by some morphological characters (Takahashi and Sohma, 1982 ; Juniper, Robins, and Joel, 1989 ; Conran, Jaudzems, and Hallam, 1997 ).

It's heavy reading, so draw your own conclusions... :mrgreen:

[CactusChris]

Great - thanks Aidan - I had seen one of those. So the quick conclusion is that drosera, byblis and drosophyllum developed glands and carnivory separately - and from very separate ancetors(?).

Interesting stuff

It seems to be a coincidence that byblis and drosophyllum also developed 'revese curl' on the leaf unfurling. This property is quite rare isn't it?

BR

Chris

[Bob H]

Assuming plastid genes cannot be lost or altered during evolutionary selection.

[Giles_KS]

Chris,

This paper is the most relevant to your question, but unfortunately I think only the abstract is freely available online.

Molecular Phylogeny of Caryophyllidae s.l. Based on MatK Sequences with Special Emphasis on Carnivorous Taxa

The way I see it, there was probably a sticky carnivorous ancestor for Dionaea, Aldrovanda, Drosera, Nepenthes, Drosophyllum & Triphyophyllum, as well as for the non-carnivorous members of the Dioncophyllaceae and Ancistrocladaceae (about 15 species of climbing plants). I think the common carnivorous ancestry is indicated by similar gland structures in Drosera, Drosophyllum & Triphyophyllum, so carnivory seems to have been lost in the other species. Byblis doesn't appear to be related to this group.

I don't think the reverse leaf curling (anticircinate vernation) occurs in any other genera, not even Triphyophyllum. I find it very surprising that this unusual feature is drawn wrongly for all the Byblis species in Allen Lowrie's CPs of Australia vol. 3

Giles

[CactusChris]

Hi Giles,

Thanks for 'anticirinate vernation' - I was looking for that. I notice that Darwin did not even seem to notice it, probably concentrating too much on the glands and whether they absorbed nutrients. Are you saying that reverse leaf curling occurs only in Drosophyllum and that it does not in Byblis or that it does in Byblis (I had it in my mind that it did) and the AL drawings were incorrect and did not show it? (one day i will buy his books...)

Am I correct in reading into your words that Drosophyllum is the only genus with this - or do you mean the only CP genus. If there are others what are they? I must say I can't think of any - but I am a horticulturalist rather than a botanist so that may not be surprising.

My latest sowing now has two out of three seeds up and growing well, but it is still early days....

One thing i do not understand with drosophyllum is that as it does not have tentacles that move how does it maximise the surface area of contact between the plant/glads and the prey?

BTW - I was hoping to find out what the reference was where Roth first mentioned drosera and carnivory - circa 1782 or so - does anyone have this reference that could send me a copy - I'm assuming it was in german - if so I can probably do a poor translation, but if it is in something other than german, french or English I will have to find someone to translate it for me.....

Best Regards

Chris

[Giles_KS]

Hi Chris,

Sorry if my post was unclear, I meant only in Drosophyllum and Byblis. Allen Lowrie's drawings show Byblis leaves unfurling like a fern, from the inside, even though the photos in the same book clearly show the opposite.

Giles

[CactusChris]

Hi Giles,

It is me not reading it correctly i'm sure.

This is really interesting, so these two genera show this trait and no others. Darwin did not spot this in his CP book, I must get Lloyd out and check what he said.

Arn't plants wonderful

Best Regards

Chris

[Greg Allan]

I'd like to add that Byblis gigantea leaves don't unroll at all. They just emerge from the growing point and grow longer, remaining fairly straight. Also, I have noticed that Byblis liniflora leaves sometimes bend backwards, so that they appear to be unfurling in the same way as Drosera filiformis leaves. This could account for the inaccuracies in Lowrie's drawings.

Chris, although I know very little about the biology of Drosophyllum, I have observed that when my plant catches a fly, it produces a lot of extra fluid that engulfs the prey. This seems to slowly drip down the leaf, presumably being reabsorbed into the plant along with the nutrients from the prey. I have also noticed a similar occurence on my Byblis gigantea, although there seems to be some dispute as to whether any of the Byblis produce digestive enzymes.