Gavrilets, S. 2000. "Waiting time to parapatric speciation"
Proceedings of the Royal Society London B 256 : 2483-2492
ABSTRACT
Using a weak migration and weak mutation approximation, I study the average
waiting time to parapatric speciation. The description of reproductive
isolation used is based on the classical Dobzhansky model and its recently
proposed multilocus generalizations. The dynamics of parapatric speciation is modeled as a biased random walk performed by the average genetic distance
between the residents and immigrants. If a small number of genetic changes is
sufficient for complete reproductive isolation, mutation and random genetic
drift alone can cause speciation on the time scale of 10-1000 times the
inverse of the mutation rate over a set of loci underlying reproductive
isolation. Even relatively weak selection for local adaptation can dramatically
decrease the waiting time to speciation. The actual duration of the parapatric
speciation process (that is the duration of intermediate forms in the actual
transition to a state of complete reproductive isolation) is shorter by orders
of magnitude than the overall waiting time to speciation. For a wide range of
parameter values, the actual duration of parapatric speciation is order one
over the mutation rate. In general, parapatric speciation is expected to be
triggered by changes in the environment.