Re: No island fossils

On Mar 8, 9:12 pm, Tim Tyler <seemy...@xxxxxxxxxxxxxx> wrote:
Lorentz wrote:
I don't think "islands in the sea" are actually the most
productive means of isolation for stimulating evolution.
Caves and mountains represent other types of isolation,
Freshwater lakes can be isolation - for fishies.
Glaciation and deserts could also produce isolation.
It is normally the interior -
I think my point is that all these environments can form pockets
of isolation. Furthermore, these pockets don't have to last millions
of years, just maybe a few thousand. The pocket has to be isolated
just long enough to form a hybridization barrier. Once the subspecies
has formed a hybridization barrier, even a partial hybridization
barrier, it has the potential of becoming a new species and eventually
a new class of animals.
The hybridization barrier in effect becomes a portable island. The
animal is embedded in its pocket of isolation. The pocket will grow
deeper with time. Maybe a hole in the pocket will form, generating a
taxon much higher than species. Even a difference in mating behavior
can start the evolution ball rolling.
Suppose the environmental pocket stops being isolated. If the
hybridization barrier is partial, then a new species can form by
hybridization or by selection. Animals with the partial hybridization
barriers are selected to avoid the other animals. If the
hybridization barrier is complete, essentially a reproduction barrier,
natural selection will proceed to make this new species far different
from the other one.
Look at the Amazon. Every meander of the river contains different
"species" of salamander. But these are only new "species" in the sense
of hybridization barrier, for the differences are slight. Surely,
these breaks in river last only a few thousand years. However, once
there is a hybridization barrier one has a portable form of isolation.
When the river system starts shrinking, these different "species" will
compete among themselves. Then larger differences will be seen.

.

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