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12046[AZ] Re: 4ns and 2ns: Where We are Now : Change in Thinking

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  • sjperk5
    Feb 2, 2009
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      Bill

      I respectively disagree with your position.

      Here is the paper on line

      http://www.lib.ncsu.edu/theses/available/etd-03112008-
      225130/unrestricted/etd.pdf

      Here is the conclusion

      No diploid R. austrinum or R. atlanticum was found despite extensive
      sampling of taxa from diverse sources and geographical origins (26 R.
      austrinum and 30 R. atlanticum accessions collected throughout the
      Southeast). The assessment of these species as diploids in previous
      studies was based on a much more limited sampling (Ammal, 1950; Li,
      1957; Sax, 1930). Therefore it seems unlikely that the lack of
      diploid forms of R. atlanticum and R. austrinum in this survey
      represents a sampling limitation, but rather a predominance of
      polyploids in these species. This appears to be the case for R.
      calendulaceum as well, where there are no reports (present study
      included) of diploid populations.

      Now yes Ranney did find that some things called austrinum were 2n and
      3n but these are in my opinion and of the author are most likely not
      austrinum had instead have been previously misidentified. The 2n
      austrinmum came from the Biltmore Estate and the 3ns from the North
      Carolina Arboretum. No plants thought to be austrinum in a native
      population were anything but 4ns. The same was true of atlanticum.

      Note: There were also some 4n flammeum not collected in the wild.

      Note: But all of this has at least 3 major problems. One the
      definition of species is not very precise. Two nature is not so
      simple. Three and most importantly Ranney and Hall start by assuming
      that species are as previously outlined and then go from there.

      Despite these problems and the newness of the technigues employed it
      is my position that the 3 findings outlined previously are simply too
      supporting of one another to not be taken seriously.

      Evidence is evidence and conclusions are just that conclusions and
      you have every right to come to your own.

      John Perkins
      Salem, NH




      --- In azaleas@yahoogroups.com, "William C. Miller III" <bill@...>
      wrote:
      >
      > John,
      >
      > Regarding Ranney's findings: If you take another look at Jones,
      Ranney,
      > Lynch, and Krebs, you will note that Ranney (ARS, Vol 61, No. 4,
      Fall
      > 2007, pp 220-227) found /austrinum/ to be 2n, 3n, and 4n using
      flow
      > cytometry. I think that's a significant finding given the relative
      > small power of the sample size.
      >
      > If Hall selected a different sequence of the genome to evaluate,
      what is
      > the possibility that an entirely different clade relationship might
      be
      > revealed?
      >
      > Bill
      >
      >
      > sjperk5 wrote:
      > >
      > > For many years the common belief, excluding canadense and vaseyi,
      was
      > > our native azaleas liked to cross with one another and produce
      > > fertile offspring.
      > >
      > > What was interesting is R. calendulaceum a known 4n for a long
      time
      > > seemd to be able to produce fertile offspring in both directions
      with
      > > known 2ns. Now crossing 4ns and 2ns should usually produce
      nonfertile
      > > offspring but in native azaleas the literatures was full of
      > > documented cases of fertile offpring from such crosses being the
      norm.
      > >
      > > For years R. calendulaceum and R. austrinum have been crossed to
      > > produce fertile hybrids. Dodd, Aromni, Sommerville, and many
      others
      > > have produced numerous beautiful hybrids using this combination.
      > >
      > > The theory was R. calendulaceum had some magicial powers to make
      > > crosses with the 2n native azalea not result in nonfertile 3ns but
      > > instead fully fertile 4ns. This magic power had something to do
      with
      > > R. calendulaceum being merely a 4n R. cumberlandense or a special
      > > unreduced combination of R. cumberlandense and other native 2ns.
      > >
      > > Three events changed the thinking. Ranney showed using new
      counting
      > > technigues that austrinum and atlanticum where 4n. Hall showed
      that
      > > the 4ns and 2ns were at least in nature not crossing to any great
      > > extend but instead formed distinct clades. Hybridizers of native
      > > azaleas doing controlled crosses in the north and south were
      finding
      > > that 4n X 2n were almost never successful and that 2n X 4n seemed
      to
      > > usually produce infertile offspring.
      > >
      > > Hall showed that R. cumberlandense and R. calenducaleum are in
      fact
      > > not all that closely related. R. calenducaleum is more closely
      > > related to luteum, austrinum, atlanticum, colemanii, canadense,
      and
      > > molle than to any of the memebrs of the 2n clade including R.
      > > cumberlandense.
      > >
      > > So three different approaches to analyzing our native azaleas
      seem to
      > > have converged on instead of our native azaleas being one large
      > > interbreeding collection of species they are instead divided into
      2
      > > clades along basically ploidy lines that are reluctant to share
      DNA
      > > across multiple generations.
      > >
      > > John Perkins
      > > Salem, NH
      > >
      > >
      >
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