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Drosera (x)? anglica

Dexenthes

Aristoloingulamata
So after reading Cthulu's giveaway thread I was alerted to the fact that some believe D. anglica to be a hybrid between D. rotundifolia and D. linearis. I guess I am confused because whereas D. anglica can be found locally in my area in various localities, I have never seen a D. linearis before. Or maybe all the D. anglica I have seen were actually D. linearis? Somebody help me on this one. . . Are these plants actually D. linearis?





 
Where did you see those plants?
 
These are in southern southeast Alaska.
 
Drosera anglica appears to have hybrid origns between D. rotundifolia and D. linearis. The cross between these two species is sterile. However alloploidy (doubling or more of the chromosomes) can occur randomly to produce fertile seeds (and offspring).

John Brittnacher's write up on Drosera chromosomes explains it much better than I ever will:

http://www.carnivorousplants.org/cp/DroseraChromosomes.php
Drosera anglica

Drosera anglica
is a widespread tetraploid, 2n=40, species of known hybrid origin. Its parents are the diploid, 2n=20, Drosera rotundifolia and the diploid, 2n=20, Drosera linearis. Drosera anglica and Drosera rotundifolia are found in North America, Europe, and Asia while Drosera linearis is only found in North America in a narrow range from Montana to the Canadian Maritime provinces. Drosera rotundifolia and Drosera linearis form sterile, homoploid, 2n=20, hybrids where they grow together. As with Drosera x hybrida and triploid progenitor of Drosera tokaiensis, this homoploid hybrid will generate neo Drosera anglica at a very low rate. However it is obvious from its very extended distribution that Drosera anglica has been around for a long time. It would be interesting to study Drosera anglica across its full range to see if populations in different areas can be traced to different polyploidization events and to see the full extent that the peripheral populations have genomic differences from the populations with the neo individuals. Studies of the neo allopolyploid Tragopogon species have shown that those species had more than a dozen progenitors across numerous locations. But those populations and new species are too young to show what happens after an extended period of time as the genome(s) of the new species evolve. Drosera anglica is a good candidate for exploring genome evolution because it has populations with old and young lineages

The notation Drosera ×anglica is not commonly used. Schnell made the argument that the cross "×" should only be used on sterile natural hybrids, if it is fertile it should be treated more or less as a species - this pretty much goes back to old definitions of species.
 
Dexenthes - those are some sweet photos!
 
These are in southern southeast Alaska.

D. linearis is not known to be that far west.

http://ontariowildflowers.com/main/species.php?id=147

They're easy enough to identify between D. anglica by the seed:

D. linearis: Seeds black, oblong-obovate, rhomboidal, 0.5-0.8 mm. long, densely and irregularly crateriform.
D. anglica: Seeds black, sigmoid- fusiform, 1-1.5 mm. longitudinally striate-areolate
 
Don't forget that Drosera anglica is also known, from several different areas in the Hawaiian islands. Yet, so far as I know, no other native CP, of any kind, are found there - not even either, assumed parent species. If Drosera anglica did develop from hybrids of Drosera rotundifolia with Drosera linearis, it is natural to speculate how this species managed to arrive at its present distribution.

Though I've visited several areas, in many parts of the world, where Drosera anglica is known to be native, the only region I've actually seen them, was at various locations in the cascade mountains of Washington state. Though I usually observed Drosera rotundifolia growing nearby, that was not always the case, either. And when they were growing near each other, they did not seem to appreciate similar micro-environments. The Drosera anglica almost exclusively chose to grow on rotten logs or small rotten branches that were floating in the water, or nearly submerged, while Drosera rotundifolia chose slightly less waterlogged locations.

Your photos seem to show a Drosera anglica, with somewhat longer lamina than usual, but not quite as long or parallel-sided, as Drosera linearis. Very nice, though.

- / - / - /
It seems, that a little, expensive, genetic analysis, to compare Drosera anglica with Drosera rotundifolia and Drosera linearis, might be able to increase the confidence of this hypothesis, as Mr. Brittnacher has speculated. I, for one, would certainly appreciate seeing the results of such testing.
 
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Thanks for the input guys. I guess this is a really interesting subject for me because it would seem that it could very well be possible that D. anglica is of hybrid origins, however, given the Hawaiin populations as well as all the other populations on various continents where D. linearis are not present, that it seems almost nonsensical to discuss its theoretical hybrid origin?

I mean... one of the hypothetical parents in some cases is separated by oceans from their progeny. :scratch:

Couldn't many species of Nepenthes be referred to as hybrids in a similar respect? N. macrophylla comes to mind. It doesn't seem that far from reality to imagine that N. macrophylla is actually an ancient ingressed hybrid between N. lowii and N. edwardsiana. If so, there could be many more carnivorous plants that could get referred to by their theoretically ancient hybrid names instead of the species name that was given to them?

Also, Joseph, I agree that D. rotundifolia and D. anglica prefer slightly different microhabitats. Although I have found the D. anglica in my area almost exclusively grow on the margins of ponds amongst grasses and reeds, whereas D. rotundifolia can be found in a wide variety of habitats, even sometimes being in woodlands.
 
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Drosera tokaiensis is another plant believed to be from hybrid origin that is D. spatulata x rotundifolia
 
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  • #10
Introgressive hybridization is a well-accepted precept for some mechanisms of speciation. And polyploidy can be part of the process, as well.

I'm sure that Nepenthes are also involved in the speciation process.

I remember, the very first time I saw wild Drosera rotundifolia. It was adjacent to a little copse of evergreen trees, the copse of trees were facing south, towards the north shore of Lake Michigan, there on Michigan's upper peninsula. I stopped at this spot, because there was a clearing in the overgrowth, and a small sandy beach, where the lake was easily visible. This was while I was on my way to visit Big Manistique Lake, hoping I would see other CP at that lake. Anyway, I was standing, with my back to the trees, and facing the lake, there was a small sand dune between me and those trees. This created a small protected depression, and provided a little shade for the back of the dune and the depression. I was a little frustrated that I hadn't spotted any CP, yet, but just as I was giving up at this location, I turned towards the back side of the dune and Lake Michigan, preparing to climb out of the depression, when, out of the corner of my eye, I noticed that the back side of the dune top (the side facing north, towards the trees), was covered with Drosera rotundifolia plants. These wild plants were the first ever Drosera rotundifolia plants I had ever seen - they were, beautiful, and they immediately stopped me in my tracks. At that angle, they were a little backlit, and sparkled in the sunlight. As I examined them more closely, I was surprised to see that some had rabbit dung stuck on their leaves. Ahh, memories. That was in the late 1970's.
 
  • #12
D. anglica probably started out a very localized plant (though at one point the habitat of D. linearis was also far more widespread), however has since been widely distributed due to waterways and, in the case of the Hawaiian populations, migratory bird routes.
 
  • #13
Here is Hudson's 1778 description of Drosera anglica (#3). He also describes Drosera longifolia (#2) which is now considered a synonym of D. anglica from examination of herbarium specimens. All the habitats listed are in England.


Here is Goldie's 1822 description of Drosera linearis. He notes in appearance it looks like an intermediate (hybrid) between D. anglica and D. filiformis.

The type specimen was collected from around Lake Simcoe, Ontario, Canada and is the Kew Garden Herbarium.

Drosera anglica
was not described as having hybrid origins until 1952 by Lepage and Williams.

I have found no literature citations, historical records (herbaria speciemens), paleontological records or mitochondrial RNA studies to show Drosera linearis ranging in either Europe or Asia. If you know of any such citations I would be most interested in knowing what they are.
 
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  • #14
D. anglica probably started out a very localized plant (though at one point the habitat of D. linearis was also far more widespread), however has since been widely distributed due to waterways and, in the case of the Hawaiian populations, migratory bird routes.

Are you saying coconuts are migratory :p
 
  • #15
I never said D. linearis was once found outside North America. Fens however were once more widespread on this continent. D. anglica, being a far more adaptable plant in terms of tolerable habitation, had no such limiting factor which likely allowed it, like D. rotundifolia, to flourish further than that of the original linearis parent.
And kula, not quite sure what you're trying to get at there... but coconuts are spread by currents, and plants don't move once sprouted, so they can't be migratory.
 
  • #16
If Drosera anglica is the fertile polyploid hybrid of Drosera rotundifolia and Drosera linearis, which somehow migrated to Hawaii, Japan, and most of the northern temperate hemisphere. In all the time it must have taken to colonize so far and wide, how then did it manage to avoid South America and any other tropical locations.

Just makes me wonder, even more, what a comparison of the genetic fingerprints of Drosera anglica, Drosera rotundifolia, and Drosera linearis, from various locations throughout their ranges, and comparing them, would show.

For me, it also has me wondering about the history and genesis of the entire Drosera genus.
 
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  • #17
I never said D. linearis was once found outside North America. Fens however were once more widespread on this continent. D. anglica, being a far more adaptable plant in terms of tolerable habitation, had no such limiting factor which likely allowed it, like D. rotundifolia, to flourish further than that of the original linearis parent.
And kula, not quite sure what you're trying to get at there... but coconuts are spread by currents, and plants don't move once sprouted, so they can't be migratory.




humor. Dating myself again.....
 
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  • #18
Abstract from "Cytotaxonomical study of the species and natural hybrids of genus Drosera (Droseraceae) in Quebec," (Gervais and Gauthier 1999).

A cytological study of 25 individuals from different Drosera populations shows that the chromosome number of the four taxa occurring in Quebec confirms the results already published for these species and does not vary. Drosera rotundifolia L., D. intermedia Hayne and D. linearis Goldie possess 2n = 20 chromosomes, while D. anglica Huds, has 2n = 40. Three different hybrids however were detected: D. rotundifolia x D. linearis (2n = 20), D. linearis x D,. anglica (2n = 30) and D. rotundifolia x D. anglica (2n = 30). The occurrence of the latter hybrid, well known in Europe and Japan (D. x obovata Mert. & Koch), is cytologically confirmed for the first time in eastern North America. The name D, x linglica Kusakabe ex Gauthier & Gervais is suggested for the linearis-anglica hybrid. while D. x woodii Gauthier & Gervais is proposed for the linearis-rotundifolia progeny. The existence of spontaneous crosses involving D. rotundifolia, D. anglica and D. linearis is consistent with the hypothesis that D. anglica is an amphiploid resulting from the chromosome doubling of the sterile linearis x rotundifolia hybrid. The meiotic pairing configurations observed in a linearis x anglica (2n = 30) hybrid suggest however that the process must have taken place with a primitive D. linearis somewhat different from the present species. D, linearis is a species with narrow ecological requirements whose northeastern American lineage with some isolated western populations alone subsist and need protection.

Interesting conclusion, however I can't find the full text to see how they further support this...
 
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  • #19
Very interesting indeed...

I have to say though, I have trouble thinking of it as anything other than D. anglica - the species. It just seems rather extraneous to refer to it as a hybrid, seeing as the hypothetical hybridization event was long enough ago that D. linearis was "somewhat different" than the present day species.
 
  • #20
Abstract from "Cytotaxonomical study of the species and natural hybrids of genus Drosera (Droseraceae) in Quebec," (Gervais and Gauthier 1999).

Interesting conclusion, however I can't find the full text to see how they further support this...

Download it here - in French - get Peatmoss to translate :p

http://www.tandfonline.com/toc/tabg20/146/4

Looks like they are calling the sterile hybrid Drosera × woodii

Schlauer argues that (Carniv. Pl. Newslett. 39(2): 46. 2010) :

As noted before (Carniv. Pl. Newslett. 37:118-119, 2008), there can be only one legitimate name
for all hybrids (including hybridogenic stabilized segregates) between two taxa at the rank that distinguishes
the two parent taxa. In the case of Drosera linearis and D. rotundifolia as the parents (which are
distinguished at species rank), this name is D. anglica. This has led to the relegation of the back-cross
that has been known for a long time at the illegitimate rank of species (as D. × obovata) to a variety of
D. anglica.
There are two further, naturally occurring hybrid taxa that involve the same parent species, viz. the
primary, diploid hybrid that is usually sterile (as opposed to D. anglica var. anglica that is amphiploid
and fertile) and that has been likewise named at the nomenclaturally inappropriate rank of species (as
D. × woodii) and the back cross of D. anglica var. anglica with D. linearis that had first been created
in horticulture before it was described from several localities in the wild. Also the latter has received a
name at species rank (D. × linglica).

The purpose of this note is to validate the respective nomenclaturally acceptable (i.e. infraspecific)
combinations for the above mentioned taxa. As both are usually sterile and not dominant over their
respective parents, they depend on the presence of the parent taxa for their existence and persistence,
leading to sympatric distribution, which is recognized by varietal rank by the present author.
(emphasis mine)

Drosera anglica nothovar. woodii (Gauthier & Gervais) Schlauer comb. & stat. nov.
Basionym: Drosera × woodii Gauthier & Gervais, Acta Botanica Gallica 146: 395 (1999)

Drosera anglica nothovar. linglica (Kusakabe ex Gauthier & Gervais) Schlauer comb. & stat. nov.
Basionym: Drosera × linglica Kusakabe ex Gauthier & Gervais, Acta Botanica Gallica 146: 393
(1999)

Donald Schnell has taken the stance that amphiploid or otherwise fertile hybrids should be treated as species. This goes back to Darwin's definition of species (fertile interbreeding).

Summary:
<table width="530" border="1" summary=""><tr><td><b>Author</b></td><td><b>amphiploid (2n=40)*</b></td><td><b>diploid (2n=20)</b></td></tr><tr><td><b>Schnell</b></td><td><i>D. anglica</i></td><td><i>D. × anglica</i></td></tr><tr><td><b>Gauthier & Gervais</b></td><td><i>D. anglica</i></td><td><i>D. × woodii</i></td></tr><tr><td><b>Schlauer</b></td><td><i>D. anglica</i> var <i>anglica</i></td><td><i>D. anglica</i> var <i>woodii</i></td></tr></table>*fertile
 
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