[Re:] families, biogeography, evolution.....

[Thomas Schlemmermeyer]

>If Croizat's contention that ancestors are widespread relative to the
>distributions of their vicariant descendants, then bottlenecks may be
>less a primary feature of evolution than many might suppose.

Let's say in one point on earth a new species arose in some unique,
peculiar, extremely localized "centre of origin".
Let's suppose that this species has a very poor dispersing power.

It would be worth to calculate it through, but I think even under those
circumstances (centre of origin, low dispersion) the species would quickly
fill out the whole space suitable as habitat, until coming to some geological
or ecological limit line.
What I want to say is the following: Let dispersion be as slow as it may be, it
will still be very much faster than tectonic events at a geological time scale.
Or in other words: Maybe Croizat's idea of wide-spread ancestors does not
contradict the assumption of small centres of origin. It might be rather
a question of scaling time. At the point of time when the ancestor is
widespread, he is so due to the result of dispersion which has already
happened before.
But the time between origin and reaching maximal distribution might be
very small when compared with the geological time scale.

But, what is orthogenetics?

   Thomas

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Thomas Schlemmermeyer
Museu de Zoologia, Universidade de Sco Paulo
Caixa Postal 42694
CEP 04299-970
Sco Paulo, SP, Brasil