Each new form,
also, as soon as it has been much improved, will be able to spread
over the open and continuous area, and will thus come into competition
with many others. Hence more new places will be formed, and the
competition to fill them will be more severe, on a large than on a
small and isolated area. Moreover, great areas, though now continuous,
owing to oscillations of level, will often have recently existed in a
broken condition, so that the good effects of isolation will
generally, to a certain extent, have concurred. Finally, I conclude
that, although small isolated areas probably have been in some
respects highly favourable for the production of new species, yet that
the course of modification will generally have been more rapid on
large areas; and what is more important, that the new forms produced
on large areas, which already have been victorious over many
competitors, will be those that will spread most widely, will give
rise to most new varieties and species, and will thus play an
important part in the changing history of the organic world.
We can, perhaps, on these views, understand some facts which will be
again alluded to in our chapter on geographical distribution; for
instance, that the productions of the smaller continent of Australia
have formerly yielded, and apparently are now yielding, before those
of the larger Europaeo-Asiatic area. Thus, also, it is that
continental productions have everywhere become so largely naturalised
on islands.
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