New species like callosum - Vietnam?

[Eric Muehlbauer]

"But then, as you say, you have a different species ... and if that happened in the wild ... then the original tetraploid "specimen" must have become immediately isolated and must have propagated vegetatively only .... ????
How the hell would that work???"
True....but, given the 1000's of years that these plants are growing and reproducing in this area....in the case of R. calendulaceum, the Appalachians, where there is (or at least was) tremendous diversity of azalea species, variants, and natural hybrids, if you have more than one tetraploid mutation in the pollinator's area, you could have successful progeny of those plants. From that point on, the tetraploid population would increase, eventually forming what I would imagine a taxonomist would consider a valid species. At any 1 moment in time, the likelihood of 2 tetraploid mutations appearing at the same time in the same area is very low...but given the 1000's of years, possibly more if the parent species shifted south during glaciations, wouldn't the likelihood be much greater?

 

[Braem]

For anyone who is interested, here are a few Wikipedia articles that mention tetraploid or other higher ploidy populations in various plants. I'm sure anyone could easily locate more detailed and scholarly sources if they want to.

Utricularia inflata
Rosa acicularis
Asplenium scolopendrium
Acorus
Solidago altissima
Campanula rotundifolia
Liatris bracteata

Maybe you noted that there is no orchid involved. And maybe you can show the evidence that you talk about "populations" from the wild ... and by evidence, I mean the chromosome counts, etc. Maybe you can read up on meiosis in any textbook ...

 

[Braem]

"But then, as you say, you have a different species ... and if that happened in the wild ... then the original tetraploid "specimen" must have become immediately isolated and must have propagated vegetatively only .... ????
How the hell would that work???"
True....but, given the 1000's of years that these plants are growing and reproducing in this area....in the case of R. calendulaceum, the Appalachians, where there is (or at least was) tremendous diversity of azalea species, variants, and natural hybrids, if you have more than one tetraploid mutation in the pollinator's area, you could have successful progeny of those plants. From that point on, the tetraploid population would increase, eventually forming what I would imagine a taxonomist would consider a valid species. At any 1 moment in time, the likelihood of 2 tetraploid mutations appearing at the same time in the same area is very low...but given the 1000's of years, possibly more if the parent species shifted south during glaciations, wouldn't the likelihood be much greater?

Yes, but then you have a different species ... that is how speciation works (most of the time) ... mutation and isolation and "lots of luck" over a long period of time. And that happens ... after all we are all hybrids of some kind. But that is not the point in this issue ... the point is that everytime someone finds a single plant that is wider, taller. higher, has "bigger flowers" they start screaming "tetraploid". A tetraploid is a plant of which the chromosomes have been counted and have proven to be 4N instead of 2N ...
And if those tetraploid "populations" of Rosa acicularis, Campanula rotundifolia, etc. exist (in the wild that is) ... then explain how they got there? Because how would a tetraploid specimen have been isolated. Obviously at the origin there was a diploid population ... so why and how did the diploid specimens all disappear ... and if there was crossing ... then the progeny was triploid and therefore most probably infertile .... Thus the population would have died out .....

 

[KyushuCalanthe]

I wish I was smart!

Some individual plants are ... but not "species". A "species" is a population of individuals. A "species" is never a single plant.

And yes, the counting is eucledian mathematics ... one, one more, one more ... and that is done under a microscope after you make the chromosomes visual im metaphase by a very complicated, time consuming and difficult procedure.

Cool! That's what I like, a sense of humor

As I said, I wouldn't know specifically, having never personally counted any chromosomes (lots of algae though), still, I've seen repeated references to R. calendulaceum being tetraploid. A few studies from the net:

Chromosome Studies in the Azaleas of Eastern North America (Hui-Lin Li, American Journal of Botany, 1957) - an extract from the abstract :rollhappy:

Chromosomes of 15 species of Rhododendron, series Azalea, subseries Luteum, were studied from 271 plants gathered from 21 states in eastern North America. Both somatic cells from stem tips and pollen mother cells were examined. The study reveals that the majority of the species are diploid with n = 13, and 2n = 26. A tetraploid species R. calendulaceum may have arisen by polyploidization, in part at least from the diploid R. cumberlandense. Hybrids of R. calendulaceum and diploid populations are mostly tetraploid, but triploids occasionally occur. (Diploid hybrids identified in the field as involving R. calendulaceum probably do not actually involve that species at all.)

Less scholarly, but a more recent extract from an online article out of the Journal of the American Rhododendron Society (Martha Prince, 1981):

The Flame Azalea is a tall plant (up to fifteen feet.) Botanically,, the most interesting feature is that it is the only one of our eastern azaleas in the Luteum subseries which is tetraploid. That means there are twice the usual number of chromosomes; as chromosomes come in pairs (and the azalea number is 13), 2N = 52. This accounts for the variety; the genetic "pool" is enormous.

Yet, another study entitled "Variation and Phenological Forms in Rhododendron calendulaceum" in Castanea (Southern Appalachian Botanical Society, 1976) makes reference to this species being tetraploid:

Rhododendron calendulaceum (Michx.) Torrey is the only tetraploid azalea native to the southeastern United States (2n=52)(Janaki Ammal et al., 1950).

And so on...

Can they all be wrong

 

[Pete]

ive only read bits of this thread, but stomata size and density has been documented to be an effective indicator of polyploidy when assessing plants that have been treated.

 

[Pete]

oh ya, and im with dr. braem. polyploids (tetrapolids) do occur naturally, but would almost certainly not occur as large populations, but rather one or a few individuals that are rare mutations of "chance" polyploidy. if entire populations of plants appear as if they are all polyploids of a highly similar species, chances are that it is indeed a geographically isolated variant that has become stabile for whatever reason of fitness.

 

[Pete]

tom ive got unlimited articles about polyploidy in angiosperms if you want some..

 

[Pete]

just found a paper that states that when a (chance/mutation) polyploid is present in a population it can attract a potentially entirely different suite of pollinators, which would then select for any other polyploids, be less likely to backcross to diploids etc. so, theoretically it sounds like it could be possible to establish small populations of polyploids naturally

 

[Rick]

I can also think of 2 documented cases of polyploids in lizards too. In these cases they exist as hybrids of two adjacent species where the resulting hybrid ends up with and odd number ploidy and the resulting "new" species is a parthenogenic population. Though quite isolated these are self sustaining populations. Ain't nature crazy?

 

[Braem]

Cool! That's what I like, a sense of humor

As I said, I wouldn't know specifically, having never personally counted any chromosomes (lots of algae though), still, I've seen repeated references to R. calendulaceum being tetraploid. A few studies from the net:

Chromosome Studies in the Azaleas of Eastern North America (Hui-Lin Li, American Journal of Botany, 1957) - an extract from the abstract :rollhappy:

Chromosomes of 15 species of Rhododendron, series Azalea, subseries Luteum, were studied from 271 plants gathered from 21 states in eastern North America. Both somatic cells from stem tips and pollen mother cells were examined. The study reveals that the majority of the species are diploid with n = 13, and 2n = 26. A tetraploid species R. calendulaceum may have arisen by polyploidization, in part at least from the diploid R. cumberlandense. Hybrids of R. calendulaceum and diploid populations are mostly tetraploid, but triploids occasionally occur. (Diploid hybrids identified in the field as involving R. calendulaceum probably do not actually involve that species at all.)

Less scholarly, but a more recent extract from an online article out of the Journal of the American Rhododendron Society (Martha Prince, 1981):

The Flame Azalea is a tall plant (up to fifteen feet.) Botanically,, the most interesting feature is that it is the only one of our eastern azaleas in the Luteum subseries which is tetraploid. That means there are twice the usual number of chromosomes; as chromosomes come in pairs (and the azalea number is 13), 2N = 52. This accounts for the variety; the genetic "pool" is enormous.

Yet, another study entitled "Variation and Phenological Forms in Rhododendron calendulaceum" in Castanea (Southern Appalachian Botanical Society, 1976) makes reference to this species being tetraploid:

Rhododendron calendulaceum (Michx.) Torrey is the only tetraploid azalea native to the southeastern United States (2n=52)(Janaki Ammal et al., 1950).

And so on...

Can they all be wrong

Assuming that the studies are really scientific ... the answer is "No, they can't all be wrong" ... but that still does not answer the questions .... and it still does not mean tha tall blonds with big boobs are necessarily tetraploids.

 

[Braem]

I can also think of 2 documented cases of polyploids in lizards too. In these cases they exist as hybrids of two adjacent species where the resulting hybrid ends up with and odd number ploidy and the resulting "new" species is a parthenogenic population. Though quite isolated these are self sustaining populations. Ain't nature crazy?

But if those lizards originate from hybridization of two species, its a whole different story ... and I am afraid that we are comparing apples with oranges.

 

[KyushuCalanthe]

Assuming that the studies are really scientific ... the answer is "No, they can't all be wrong" ... but that still does not answer the questions .... and it still does not mean tha tall blonds with big boobs are necessarily tetraploids.

Man, you do have a sense of humor! :clap:

 

[Clark]

hmmmm.

 

[Eric Muehlbauer]

"so why and how did the diploid specimens all disappear" In the case of R. calendulaceum, the diploids did not disappear. The diploids are R. cumberlandense (or bakeri....I think cumberlandense is the accepted name...too bad..I prefer bakeri, but if the other has priority, so be it) and the tetraploids are calendulaceum. Having grown both, they are very similar, but calendulaceum is larger and more robust in all respects.

 

[Braem]

OK Eric, but then we have two species ... and that is OK ... but I would be interested whether calendulum was found once in the wild and then propagated in gardens or whether calendulum still occurs with cumberlandense in the wild.
and about the accepted name ... we have the rule of priority ... but not everyone abides by it ... most people still use "callosum" although "crossii" was published first etc. etc. but that is something for another thread maybe.

 

[KyushuCalanthe]

There is an apparent "hybrid swarm" of native azaleas on Gregory Bald in Smoky Mountains National Park that includes a maddening variety of flowers. Truly a wonderful place. Here's a couple links.

http://www.tjhsst.edu/~dhyatt/azaleas/new/gregoryhybrids.html

http://www.tjhsst.edu/~dhyatt/azaleas/new/gregoryhybrids.html

Truly a gorgeous place. Sorry about hijacking this thread.

 

[PaphMadMan]

One could assume that all the references to tetraploid plant populations in unscholarly publications have no basis in rigorous peer reviewed science, and that the idea nevertheless became so prevasive as to be included in college botany curricula. I am comfortable assuming otherwise.

 

[Eric Muehlbauer]

To the best of my knowledge, R. calendulaceum and bakeri are found pretty extensively in the southern Appalachians, particularly around Georgia, N. Carolina, and Tennessee. I do have a book that discusses this...I'll have to look for it.

 

[Braem]

One could assume that all the references to tetraploid plant populations in unscholarly publications have no basis in rigorous peer reviewed science, and that the idea nevertheless became so prevasive as to be included in college botany curricula. I am comfortable assuming otherwise.

Well, that is a problem ... and I tend to join you in that opinion. However (without wanting to start that discussion again), peer review is no garantee for truth in articles.