Laurasian vs. southern families/taxa

[Allan Shanfield]

Dear Taxacomers,

I am under the general, perhaps erroneous notion, that in the Great
American Interchange and in Asia during the Pleistocene that more
Laurasian families like Lauraceae, genera like Lithocarpus and more
occuped the higher elevations and perhaps outcompeted the more tropical
spp. at the time via island hopping, wind dispersal, land bridges and
more. My question is: Is it true that the Laurasian intrusion reflected a
more "hardy" stock? Also, I hear there were some exceptions in parts of
Asia. Finally, if the record does show that northern families/taxa are
hardier at higher elevations viz. more southern ones, has this hypothesis
been actually tested? (competition studies, etc)?

A corollary is that in instances where Laurasian families/taxa did not
migrate north and that the tropical plants radiated to fill montane
niches, have there been tests of ecological/structural/ecophysiolocial
convergence.

Long questions...can't find much in the literature in this regard.

If anyone has some good hints, please address them to me and I would be
especially grateful. If anyone is interested, I can either post good
sources or pass them along personally.

Thanking you in advance.

Sincerely,

Allan Shanfield

Grad. Group in Geography
UC Davis