But they were still fruit flies. No one says that there is not specialization within a species. The gene info is becoming less and more selective not greater or different. Nothing is being added.
Standard creationist blat, and typical failure to understand what evolution is, how it works, and what the results are. ALL EVOLUTION is about "specialization within a species" UNTIL it reaches such a point of gross specialization that said "specialized species" cannot interbreed with the base species.
Lions and tigers are definitely considered separate species, but they CAN produce offspring (though I believe that the resultant offspring is sterile). Certainly that is true of horses and jackasses--the resultant mule IS sterile. The two variants of fruit flies are less closely related than that, and thus, ARE different species, despite the fact of surface resemblance.
Genetic analysis has re-shuffled the deck on a lot of species family trees, showing that certain animals with a strong surface similarity are, in fact, not closely related at all.