There seemed to be no end to the tricks that [Drosophila] pseudoobscura could do: one stock had odd sex ratios, another diplayed what seemed to be maternal inheritance, and so on. ... Pseudoobscura was so full of new tricks because it was an undomesticated, wild organism that had not yet been stripped of its natural genetic diversity, as melanogaster had long since been.
In, Lords of the Fly (1994) by R.E. Kohler, University of Chicago Press (Chicago, IL). pg. 260.