Any non-aggressive folks interested in discussing taxonomy?

Discussion in 'Codex taxinomiae plantarum (CTP)' started by VAAlbert, Feb 17, 2009.

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  1. Sep 6, 2010 #101

    ohio-guy

    ohio-guy

    ohio-guy

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    I only see two strong red blotches in this image, but very interesting never the less. How far along are you in your work?
     
  2. Sep 6, 2010 #102

    VAAlbert

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    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.
     
  3. Sep 6, 2010 #103

    ohio-guy

    ohio-guy

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    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?
     
  4. Sep 6, 2010 #104

    VAAlbert

    VAAlbert

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    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.
     
  5. Sep 6, 2010 #105

    VAAlbert

    VAAlbert

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    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:

    [​IMG]

    dianthum:

    [​IMG]
     
  6. Sep 7, 2010 #106
    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
     
  7. Sep 7, 2010 #107

    NYEric

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    Very interesting, in my clones you will need to repair the near sightedness, thank you.
     
  8. Jul 10, 2011 #108

    Braem

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    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: Jul 10, 2011
  9. Mar 5, 2012 #109
    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!
     

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