Hello all!
A little info for people who care.
 
There are varying definitions for what a species is and it can become very
confusing the more one studies the question. The main definition taught today
in classes is what is known as the Biological Species Concept (BSC). Mayr, one
of the founders of the the BSC, states in his book "This is Biology" that a
species is, " A reproductively isolated aggregate of populations which can
interbreed with one another because they share the same isolating mechanisms."
In actually having the honor to meet Mr. Mayr I took the opportunity to
discuss a little bit on the BSC and competing theories. He will admit that the
BSC does have its fault(s), the main one being is how does one apply it to
self-reproducing organisms (e.g. bacteria). But the most important piece of
advice he gave me is when I study a specific type of organism, treat each
"population" separately.
 
I hope that helps a bit.
 
Peace out!!
Emilio Jose