families, biogeograhy, evolution

[John Grehan]

Regarding comments by Allan Shanfield:

And what of the
>Laurasian intrusions into (many) tropical mountains - at expense of more
>Neotropical (mostly Gondwanan elements it seems from recalling Raven and
>Axelrod's paper).

Some of these "intrusions" may be more fanciful than factual, based on
the premise that there is a geographically narrow center of origin for
differentiated taxa.

A lot of "Neotropical" taxa are not Gondwanan elements at all, but Pacific.

Selection doesn't really have to be at the family level
>but rather at the individual level (godknows what problem "group
>selection" brings forth).

It my be that families or other higher taxa represent the ancestors of
the subordinate taxa, and that this ancestor not only constrains subsequent
evolution, but also may contribute to a "bias" in the subsequent evolution
of characters within the separate lineages of the descendant taxa.

>
>Thus, in the Great American Biotic Interchange (and other collisions)
>there was mixing, presumed competitions and winners that reflect at the
>family level (realizing earlier contact occured previously and back
>further likely in W and E Gondwanaland.

The "Great" American biotic interchange may not be all that great. The
exchange
did not obscure the trans-Atlantic and trans-Pacific patterns that are the
foundation of American biogeography.

>
>Superior floras? Superior spp? Is it enigmatic that in gaps Trema (a
>Laurasian) outperforms Neotropic/Paleotropical pioneers too - of course
>not always...

Such notions of "superior" might be more trouble than they are worth if
they are not predictive. If the outcome is contingent upon both biological
and environmental inheritance, then there may be no such thing as a
superior flora, fauna, or biota in a spatiotemporaly unrestricted sense.

My 5 cents worth.

John Grehan