Date: Thu, 29 Oct 1998 18:34:22 From: SCHLAUER@chemie.uni-wuerzburg.de To: cp@opus.hpl.hp.com Message-Id: <aabcdefg3448$foo@default> Subject: Re: Sarracenia evolution
Dear Bill,
> So then I asked which came first; i.e. if we are looking
> at, say, S. oreophila, is it likely that this was an evolutionary ancestor
> of S. flava - with a migration from the mountains - or the other way round.
This can almost only be speculated about in the virtual absence of
even the slightest historical data. The oldest records of
_Sarracenia_ known to mankind (or at least known to me) are not even
500 years old. This is absolutely nothing in terms of evolutionary
time scales.
The modern ranges of both _S. flava_ and _S. oreophila_ are probably
different from their original ranges at the time when both taxa
separated from a common ancestor. I assume that the range of _S.
oreophila_ fragmented after an initial spread in an originally
coherent area. This must not necessarily have been in the mountains
originally (if the climate was cooler than nowadays, it could well
have been in the plains). Now the climatic requirements of this
species are only found in the mountains, and this species seems to
be in a stage of retreat that may eventually lead to its extinction.
_S. flava_ is a (nowadays) far more tolerant and adaptable species.
It was able to spread throughout a vast area in the subtropical E of
the USA, without any obvious relation to mountains. This present
range is quite certainly of post-glacial origin (the area of
subtropical climate was considerably smaller during the glaciations),
but it is difficult to say if _S. flava_ became heat-tolerant (cf.
the recently remarkably cold-tolerant _S. purpurea_!) within its
already large range or if it spread rapidly after the last glaciation
(_S. purpurea_ must have spread to the N *after* the glaciation
because there is no realistic mechanism for range extension beneath a
solid cover of glacial ice).
> These sort of questions might find clues in the age of the mountain ranges
> compared with "estimates" of the evolutionary timescale of the plants,
> numbers which I haven't the slightest idea of.
The mountains (belonging to the Appalachian range) are certainly much
older than the plants (belonging to the angiosperms). But I fear this
will not be of much value for your phylogenetic considerations.
Kind regards
Jan
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