Biogeography of Plants in Western Amazonia

[john grehan]

>John Greham answered:
>
> > That is not correct.
> > There are innumerable case of organisms being
> > introduced into areas where they formally did not occur and have since
> > thrived.
>
>Are both statements contradictory? As long as the environment fit
>sufficiently with the needs of a species you can successfully introduce that
>species anywhere (see the ex situ greenhouse collections). On the other hand
>it would not be possible to introduce a rainforest epiphyte in a desert (to
>put it extreme :-)) even when both locations would be related geologically.
>The false positives or negatives in biogeographical data are for a great
>deal the result of the environmental needs of a given species.
>
>Guido Mathieu

The apparent contradiction may be resolved for me if the term 'can' or
'may' were used instead of 'will'. In the historical evolutionary context
the question becomes one of understanding how an organism comes to occur in
a particular set of locations that are not necessarily the entire range of
locations that are theoretically possible for a given set of environmental
conditions.

In evolutionary time it may well be possible for a rainforest epiphyte to
be introduced into a desert if it is able to 'adapt' within the constraints
of its current or future variation. In a less 'extreme' classic there are
plants that are disjunct between the seashore and inland localities in New
Zealand where the inland plants occur only around salt pans. A traditional
explanation has been chance dispersal from the coast. A panbiogeographic
model is for the coast to have moved away leaving some plants stranded
inland that could only continue to survive under a high salt environment.
They would have become extinct as predicted by Mathieu, but certain areas
maintained the necessary conditions through ground salt seepage.

Other organisms along the former coast did survive under the new
environmental parameters and are widespread although their distributions
today continue to track the former coastline. Classic evolutionary ecology
(not that one would generally find this in ecology textbooks, although if
anyone has seen this sort of thing cited I would be very interested to know).

John Grehan