Paphs and DNA analysis...

Discussion in 'Taxonomy' started by bench72, Apr 20, 2009.

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  1. Apr 21, 2009 #21

    emydura

    emydura

    emydura

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    Just trying to make sense of that cladogram. The Barbata group in particular seem to be all over the place. For example, I've always considered the following groups to be closely related species.

    callosum / barbatum / lawrenceanum
    wardii / venustum / sukhakulii
    papuanum / bougainvilleanum

    Yet from my interpretation of the cladogram they are not that closely related at all. Callosum is more closely related to wardii and purpuratum then it is to either barbatum or lawrenceanum. Papuanum is more closely related to barbatum and superbiens than it is to bougainvilleanum. Venustum and sukhakulii are closely related but not to wardii.

    David
     
  2. Apr 21, 2009 #22

    smartie2000

    smartie2000

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    I looked at it now through my university and I am suprised too. Especially with wardii and sukhakulii:confused:

    my prof also has discussed the same problems already mentioned about molecular systematics. She doesn't like Orchidaceae so much :( (I think she thinks we are nuts...)
     
  3. Apr 21, 2009 #23

    Leo Schordje

    Leo Schordje

    Leo Schordje

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    phenotypically, your groupings seem more or less correct. The DNA cladogram generated probably was based on only one short DNA segment. If you were to use 2 segments on different chromosomes, you would get a different answer, 3 segments, would yeild another answer. Until entire genomes are sequenced we have no real clue as to the significance of these DNA relationships. Since the function of the DNA segments is not very well known, it is not possible to tell how that particular segment used is a valid one for the relationship study.

    A hypothetical example: You sample a DNA segment that is conserved in one environment (say warm temps) and is unnecessary (therefore variable) in another environment (for example cool temps) it may look like 2 unrelated warm growing species are very close, because that segment was conserved. When in reality - a hypothetical cool grower could be much closer related, which would be shown if multiple DNA segments were analysed.

    Supossedly this is taken into account in more modern methods but I am skeptical, there is so little published DNA data for slipper orchids. Unless a serious look is taken at the technique and methodology for DNA studies, it is difficult to give them any credibility. Poorly chosen methods yeild less than useful information.

    Your clades based on morphology are probably more valid than the ones based on the DNA studies done to date.
     

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