This idea is based on the observation that populations living near the boundary of a less hospitable habitat are affected, because the neighboring habitats are connected by migration.
From D > 100, power starts to decrease, which is expected as highly differentiated populations are connected by migration events that are distantly spaced in time, so recombination has time to break up associations between alleles.
Such populations are connected by migration rates that are high enough to rescue local populations from extinction, but low enough for genetic drift to generate measurable genetic differences among populations [ 22].
If the frequencies of the oscillations differ sufficiently between two or more of the populations and the demes are connected by migration (i.e. gene flow), the equilibrium points in all populations become stable rather than unstable.
Yet, whether or not a lineage is indeed a phylogenetic species or e.g. represents demes from a metapopulation that is connected by infrequent migration, can be obscured.
In other words, genetic differentiation would be practically 0 even if the three subpopulations were connected by very small migration rates.
A necessary requirement, however, is that individuals comprising the separate clades correspond to different lineages or populations that themselves are connected by little or no migration, since significant gene exchange would erase the signature of high divergence among clades.
Within patches, a stepping stone of demes were connected by an appreciable level of migration (m > 0.1), while the migration rate between patches was much smaller (m bar << 0.1).
Anatomically, the retroperitoneum, mediastinum, back and neck are connected by fascial planes which allow migration of air due to pressure gradient.
