The geographic separation of populations derived from common ancestors may continue long enough so that the populations become completely differentiated species before ever regaining sympatry and the opportunity to interbreed.
"The timing of mutations must be earlier than the separation of populations," says Stanford geneticist Luca CavaLucaSforza.
The isolating factor is most often the separation of populations in geographic space (Mayr 1942).
Cospeciation may also occur independently of coevolution when speciation is caused via the separation of populations by geographic barriers such as mountain ranges (Page 1994; Roderick 1997).
One of the events that can trigger cladogenesis is the physical separation of populations, which may then differentiate and form different species.
Spatial separation of populations can also provide the opportunity to validate the generality and applicability of model predictions in the absence of long-term monitoring data.
The distribution of genetic diversity in P. cadaverina is due in large part to the separation of populations into different major watersheds and mountain ranges.
For all three of the cores, structure clustering didn't yield any separation of populations within each of them (data not shown).
Classically, this diversity has been explained through allopatric models of speciation, in which reproductive isolation arises through the physical separation of populations [1].
