Any non-aggressive folks interested in discussing taxonomy?

Slippertalk Orchid Forum

Help Support Slippertalk Orchid Forum:

ohio-guy

Well-Known Member
Joined
Dec 1, 2006
Messages
551
Reaction score
0
Location
Central Ohio
I only see two strong red blotches in this image, but very interesting never the less. How far along are you in your work?
 

VAAlbert

Well-Known Member
Joined
Nov 26, 2006
Messages
113
Reaction score
0
Location
Buffalo, NY
Sorry, my words were a little misleading --

The main loci are the 2 VERY STRONG red sites, and the 2 very strong green sites. Again, these are clusters of DNA that encode two different genes that are principal in eventually making all proteins.

By 3 red BLOTCHES, I meant the LESS STRONG red sites, of which there are three, and note that there are also 2 really weak sites (both less strong and weak sites kind of look doubled since they are on 2 chromosome arms each; the strong, strong sites are so strong that the arms are obscured). So the weak sites are homozygous, but the less-strong blotches are heterozygous. The main sites, which are VERY BRIGHT, are homozygous as well.

We're actually rather far along with the Paphs, now working our way into the Phrags and a couple of Cyps. Again, the focus is species.

Regards,

Vic.
 

ohio-guy

Well-Known Member
Joined
Dec 1, 2006
Messages
551
Reaction score
0
Location
Central Ohio
what do you think of differing chromosome counts as evidence 2 plants would be two different species? It seems to me I once read Phrag besseae and Phrag delassandroi had 2 different counts, which in my mind (if the counts were accurate/reproducible) would indicate 2 different species. Yet there is still a lot of discussion that they are just extremes of a population. do Chromosome numbers vary within a species in plants?
 

VAAlbert

Well-Known Member
Joined
Nov 26, 2006
Messages
113
Reaction score
0
Location
Buffalo, NY
Different chromosome numbers could be used as evidence for difference between species, but I'm afraid it isn't so easy. There have been reports of different chromosome numbers in Paph wardii, for example, 2n=41 or 2n=42.... and Paph venustum 2n=40, 41 or 42. Now one could claim that these numbers are identifying what could be "cryptic species" in wardii or venustum, or perhaps better stated, population polymorphism in these plants. I would go for the latter. If you have 2 populations of venustum, e.g., that are 40 and 42, then when they come into contact, some progeny of intraspecific mating will have 41. We see examples of FISH heterozygosity (remembering my figure) in SPECIES plants quite frequently, and this could just as easily be considered to result from crosses between different populations that are fixed for one chromosomal trait vs. the other.

Hope this helps,

Vic.
 

VAAlbert

Well-Known Member
Joined
Nov 26, 2006
Messages
113
Reaction score
0
Location
Buffalo, NY
more o chromosomes

Hi all:

See below some more shots of chromosomes, this time 2 species with their telomeres and telomere sequences lighting up. The top one is Paph moquttianum; the second id Paph dianthum. Telomeres are sequences that cap chromosomes to keep the ends from degrading. You'll note that there is one signal per chromosome arm in moquettianum (a little noise is visible = nonspecific staining, to be ignored), whereas there are massively hybridizing regions INSIDE chromosomes of dianthum, as well as the normal dots at the ends of the arms. We're working now on the significance of these differences, but I can tell you for sure that one thing is that chromosomal evolution in dianthum is currently more dynamic (not to say that moquettianum genomes weren't in the past -- almost had to have been since the chromosome number is higher than dianthum's, and when chromosomes split, they need more telomeres to cap their new chromosomes).

moquettianum:



dianthum:

 
D

Drorchid

Guest
Very Interesting, and thanks for posting those pics. I definitely believe Cytology is a very useful tool in Plant Taxonomy, it is also interesting to see what happens to chromosomes when you create hybrids, especially the more complex ones. For my Masters degree, I did some C-Banding techniques on Alstroemeria, and when you looked at the chromosomes of an unknown hybrid you could tell what the ancestral species where of that hybrid.

Robert
 
B

Braem

Guest
Well, for starters, I am definitely in favor of checking relationships of particular plant individuals at the DNA level. When I say individuals, I really do mean individual clones, since the extent of natural genetic variation within what looks 'the same' or similar could be rather low or rather high. Populations of plants are notorious in this aspect, and understanding individual variation within populations -- AND between them -- is very important in my view. In narrow endemics like most Paphs and Phrags, the situation of ALLOPATRY (geographically distinctness) often leads to both genetic and morphological divergence. Allopatric SPECIATION can occur if gene flow, e.g., is largely cut off between populations, leaving them to go their own way further still. This said, in plants, the definition of species is more clouded than simple lumping vs. splitting, because real reproductive isolation may not be enforced at all if 'species' come into contact. Although botanists have found many, many more examples of cryptic reproductive isolation through, e.g., partial fertility barriers than previously supposed, there are NOWHERE NEAR as many examples of gene flow between recognized species of animals -- vertebrates, say. Plants extend their promiscuousness by having the tendency to form polyploids along with hybridization events. Angiosperms go crazy with polyploidization, and it's surprising that so few natural slipper tetraploids have been identified. Polyploidy is a way out of any reproductive barrier between 'species' (or distinct populations of 'species') that might come into contact.

Going on to the issue of when a new species, subspecies, or variety might be named, this does indeed involve quite a bit of hand waving. Some (like me) would like to see biodiversity given concrete description, and the best way to preserve the intent of describing biodiversity is at the species level, since species names NEVER DIE -- they can simply be ignored if one wants. So maybe it's A-OK to name a Phrag. dalessandroi and then have most of the world consider the plant Phrag. besseae var. or subspecies dalessandroi. I don't know which of the latter names have been validly published, or which are in most common use -- the fact remains that the Latin binomial Phrag. dalessandroi is always there as a formally described entity. Subsuming Phrag. dalessandroi into besseae is merely a decision you or I could make -- nobody can rid themselves of the existence of the name Phrag. dalessandroi since it was validly described. So use it if you like, or any other valid name that might apply to a given individual plant with features that fit.

As for Phrag. schlimii vs. fischeri vs. manzurii, I guess I'd support their DESCRIPTION as species in order to get the Latin binomial on record. Of course, one could validly describe manzurii as a variety of schlimii -- accept what you want -- the same packages of biodiversity are there even if one less 'species' is on the Phrag. list.

New species especially, but also new subspecies or hybrids, create a lot of excitement in the orchid world -- folks gotta have 'em. So, any new names create markets, no matter how small the morphological differences.

Many examples of new species are dead clear -- like when Phrag. besseae or Paph. malipoense were discovered. But then the subtlties creeped in when natural variation led some to accept the species Phrag. dalessandroi and Phrag. jackii. Well, the latter two are different from the former 2, and do appear to form distinct populations, and are probably a little distinct at the DNA level. I'm glad that Phrag. dalessandroi and Paph. jackii exist as names recognizing diversity, but it just doesn't matter taxonomically if they are referred to as varieties. If one is interested in various aspects of evolutionary biology beyond taxonomy, such as population genetics, pollination interactions, or ecology, one might care more than I would.

These are my 2 cents -- rambling a bit, sorry for that. And I may change my mind on some things I wrote!

All best,

Vic.

I stumbled across this posting ... and I guess I will be regarede as aggressive ... but I don't care.

I don't quite understand why someone claiming to be a scientist can write: "I guesss I support their description as species in order to get the Latin binominal on record." What do you want to say ... descriptions just to put names on record??????

And one can validly describe any plant as species or variety or form as there is no rule deliniating a plant "species", "variety" or form.
 
Last edited by a moderator:
C

cborchids

Guest
DNA has been part of taxonomy for a while now, but as above, variation in DNA can itself be low or high within a given taxon. In our species for example there's a lot more variation in African populations than in any others, though others as in China or India are more numerous, indicating a "bottleneck" or event that limited diversity in those larger populations. In orchids, also as above, starting with gross morphology seems sensible, as we're trying to distinguish one "kind" from another, rather than drawing relationships so obscure that we'd each need equipment for analyzing DNA in order to label our plants. All that done, there's an interesting book by Simon Conway Morris (used to do prep work for Stephen Jay Gould) contending that DNA also converges through evolution, same or very similar chemical pathways used over and over, obvious example being chitin used for arthropod shells and for fibers in fungi. So, DNA wouldn't necessarily be foolproof if a researcher didn't already recognize for instance that Paphiopedilums isn't very closely related to Cattleya.

I have been amused by the question of how different a species should be to have that rank - the cochlopetalums seem pretty close to one another, compared to the mastigopetalums, for instance, and maybe not surprising as the geographical range of cochlopetalums is rather limited by comparison.

OK now back to work for me!
 

Latest posts

Top