  A classical view of speciation is that reproductive isolation arises as a
by-product of genetic divergence. Here, individual-based simulations are used
to evaluate whether the mechanisms implied by this view may result in rapid
speciation if the only source of genetic divergence are mutation and random
genetic drift. Distinctive features of the simulations are the consideration of
the complete process of speciation (from initiation until completion), and of a
large number of loci, which was only one order of magnitude smaller than that
of bacteria. It is demonstrated that rapid speciation on the time scale of
hundreds of generations is plausible without the need for extreme founder
events, complete geographic isolation, the existence of distinct adaptive peaks
or selection for local adaptation. The plausibility of speciation is enhanced
by population subdivision. Simultaneous emergence of more than two new species
from a subdivided population is highly probable. Numerical examples relevant to
the theory of centrifugal speciation and to the conjectures about the fate of
``ring species'' and ``sexual continuums'' are presented.
