From Dunbart’s Guide to Telara, Ember Isle:

One of the defining features of Ember Isle is the large number of spirits who live within its jungles. These spirits are called Telaran Spirits, because as best as anyone can tell, they seem to be born of the energy of Telara itself. They do not seem to reproduce, nor has anyone credible observed the exact method of their creation and manifestation. Folk lore of Ember Isle dictates that they are born within the sourcewells. If these sourcewells are indeed connected to the very heart of Telara, then spirits born out of them would be Telaran in the purest sense possible. However, no recent first-hand reports have confirmed that they are in fact born from the sourcewells, and folk lore cannot be regarded as truth.

It is clear that they do have some connection to the sourcewells. Ember Isle has a great many of these sourcewells, and the spirits are drawn to them as moths are drawn to a flame. The correlation between the number of sourcewells and the number of spirits is most likely not happenstance. Whether or not they simply feed on the great energy of these wells or whether they are native to the wells is, however, a matter of debate.