What do genetic tests often reveal about many historical North American subspecies classifications?

That morphological differences are superficial compared to the shared genome.

The shift in taxonomy from relying on external appearance to using molecular data demonstrates a key scientific insight into wolf evolution. In the past, slight variations in coat color or skull shape due to local environmental pressures were often used to establish new subspecies names. However, modern genetic testing frequently demonstrates that these visible, morphological differences are relatively superficial when compared against the overall shared genome of the population. This indicates a rapid, recent post-Pleistocene range expansion where populations intermingled before true, substantial genetic divergence could occur below the species level, suggesting historical subspecies boundaries were sometimes drawn too finely.