[Taxacom] Biogeographical reasoning
kinman at hotmail.com
Wed Dec 27 18:53:00 CST 2006
I believe that the two most likely and parsimonious hypotheses would be
either 1a (vicariance) or 1b (dispersal). For instance, N. menziesii has
probably always been in NZ (and I lean toward 1b being more likely than 1a;
and I'm pretty sure Knapp et al. would also agree with that). It could have
evolved elsewhere (and gone extinct in that region without a trace), but
that seems even less likely to me. Anyway, if 1b (dispersal) did occur, the
one tree of N. cunninghami that reached NZ was the founding ancestor of N.
menziesii, and thus N. cunninghami is paraphyletic (just like many other
species that have spun off new daughter species).
If it was actually vicariance (1a), the most likely scenario would
probably be a species in New Zealand barely squeaking through the Oligocene
bottleneck and founding N. menziesii in that manner, although one could
perhaps argue it was N. menziesii on both sides of the bottleneck since
species are such "fuzzy" entities in the time dimension. Luckily, dispersal
to a new island can make the break much more abrupt (and the line between
species easier to draw), and I still believe parasitic and/or symbiont taxa
will help show it was not vicariance in this case. And hopefully the same
for the dispersal of Nothofagus gunnii (or cethanica) to found the
truncata-fusca-solandri group. It isn't going to be easy or without
controversy over the interpretations, but it certainly will be interesting.
>OK, let's imagine a few possibilities for Nothofagus sp. A (NA), which is
>currently found in New Zealand (NZ):
>1. NA has always been in NZ.
>1a. NA evolved in NZ within a lineage which has always been in NZ.
>1b. NA evolved in NZ within a lineage which dispersed to NZ from somewhere
>2. NA dispersed to NZ from somewhere else.
>2a. NA evolved somewhere else within a lineage was never in NZ. (dispersal)
>2b. NA evolved somewhere else within a lineage which at one time was in NZ,
>but became extinct there. (vicariance/dispersal)
>2b. NA evolved in NZ (see possibilities 1a and 1b), became extinct there,
>and re-established in NZ from somewhere else. (vicariance/dispersal)
>From photos to predictions, The MSN Entertainment Guide to Golden Globes has
it all. http://tv.msn.com/tv/globes2007/
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