Date: Thu, 9 Jan 1997 22:48:53 -0500 (EST) From: JewelR@aol.com To: cp@opus.hpl.hp.com Message-Id: <aabcdefg145$foo@default> Subject: Re: "Dandylions"
I refered the reference to "dandylions" to Dr. Voss writer of Michigan Flora
Vol. !, II, & III just coming off the presses this week.
>Edward G. Voss wrote:
>
> I do not want to expend much time elaborating on the strange
> memo you received regarding "dandylions." I concur in your reaction!
> Everybody knows that dandelions are apomictic, although almost no one
> would accept the particular definition of apomixis stated in the memo.
> In the narrow definition, apomixis is reproduction by seed without
> fertilization; the result is, indeed, as stated: genetic identity with
> the parent plant. In a broader sense, apomixis is any non-sexual
> reproduction that tends to replace sexual reproduction and could well
> include such a phenomenon as origin in a vegetative cell. You can find
> a multitude of definitions in the literature. However, any apomict
> would be ultimately derived, would it not, from some sexual ancestor?
> Whether that derivation occurred on this continent after migration here
> or on another before migration might have some bearing on whether to
> consider a given population native or not in an area. But apomicts and
> dandelions have been studied intensively, especially by European
> botanists, for many, many years, and the whole mess is extraordinarily
> complex (see references under Taraxacum on p. 353 of my new third
> volume). I would not want to place any credence whatsoever in your memo
> without knowing WHOSE "evidence shows" and HOW one could conclude
> anything therefrom regarding nativity. If "This" also holds for other
> weeds, what is the antecedent of the pronoun "This"? Is the writer
> trying to say that other weeds are apomictic? Some are, some aren't.
> Or that others have been shown to be distinct from European relatives?
> Some are and some aren't, but genetic distinctness does not necessarily
> mean species distinctness. (White- and red-flowered plants are
> genetically distinct, but so what?). Apomixis, in one or another form,
> permits maintenance of a trivial genetic difference throughout a number
> of "individuals" which in fact are hardly to be considered different
> individuals--any more than aspen stems in a clone are different. The
> big question is, bluntly, SO WHAT? In short, I personally would pay no
> attention so so poorly documented an assertion nor beginb to list our
> common weeds as indigenous! Of course, another interpretation of what's
> behind this might be that the writer is confusing the accepted native
> dandelion species of far-northern parts of North America with the
> presumably introduced weedy species of more temperate latitudes.
> --Ed Voss
This archive was generated by hypermail 2b30 : Tue Jan 02 2001 - 17:30:58 PST