The rising mountains separated populations of Poulsenia, setting them on different evolutionary paths.
Natural selection can also cause speciation even when there is a fair degree of gene flow, especially in circumstances where geographically separated populations experience different selective forces.
However, the limited knowledge of the genetic diversity within and between widely separated populations suggests the possibility that the loss of local populations might be significant.
In a study on butterfly species from Central Asia, Lukhtanov et al. (2009) discussed how the inclusion of geographically separated populations influenced DNA barcoding.
Genetic differentiation among spatially separated populations, using biparentally and maternally inherited genetic markers, allows determination of the relative historical effectiveness of pollen and seed dispersal.
If you compare geographically separated populations within the "continental" areas, you get the exact same kind of variation.
This suggests that forest fragmentation may not completely isolate separated populations.
Nor could significant genetic differences be detected between widely separated populations of coyotes.
The kitefin shark has an almost circumglobal range in tropical and warm-temperature waters, consisting of a number of widely separated populations with likely little interchange between them.
The small number of geographically separated populations may also threaten the species' genetic health, although a 2004 study concluded that genetic diversity was still relatively high.
In addition, these constrained conditions resembled a scenario in which ecologically different situations may have triggered the formation of varying traditions in geographically separated populations.
