If allopatric speciation is the most prevalent mode of speciation, what do you predict about the geographic distributions of many closely related species? Does your answer differ for species that are sedentary versus species that are highly mobile?

It is likely that the emergence of geographical barriers among populations (such as for example, rivers, mountains, etc.) were responsible for the isolation of these species.  

Explanation:

The presence of geographical barriers among populations ensure that they begin to evolve independently and mechanisms of reproductive isolation will appear among them

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.