Geographic Barriers and Speciation

Often geographic barriers keep populations of animals from interacting. Over time, these populations become so different from one another they can no longer interbreed, becoming distinct species (a process called vicariance). Brown lemurs live in forests found around the edges of Madagascar. Look at the range map below to see where you would find each of the different subspecies we've been studying.

  1. E.f. rufus
  2. E.f. fulvus
  3. E.f. mayottensis
  4. E.f. albifrons
  5. E.f. sanfordi
  6. E.f. albocollaris
  7. E.f. collaris

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The rivers that run through the forests form natural barriers to lemur movement and separate populations. Click on the map to see how geographic barriers divide brown lemur habitat.

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How does this compare to the distribution of various brown lemur subspecies?

In some cases, a river (like the Betsiboka) clearly defines a boundary between two subspecies (E.f.fulvus and E.f.rufus). But sometimes major rivers (or even an area with lack of forest) do not. In order to help resolve questions regarding how the populations of brown lemurs became separate subspecies we can to turn to genetics.