How are new species formed?
Stage 3: Two Different Species.
However, the different dog breeds are different enough in some
cases, both due to differences in body form or DNA that some of the breeds could
in the future become separate species!
Consider a male Dachsund trying to mate with a female Great
Dane. He's going to be pretty frustrated trying to successfully mate with the
larger Dane. Or consider the female Dachsund mating with the male Great Dane.
Is she large enough to hold the hybrid puppies that might result? Will the puppies
that result be structurally able to function and survive due to the differences
in their 2 parents?
At this point, we consider the 2 breeds to be the same species
because both can still intermix their genes with other more similar breeds,
which in turn can interbreed with other breeds. Dachsunds and Great Danes are
still connected by this chain of breeding.
If the 2 breeds continue to develop away from each other, and
the connection of breeding between them to be disrupted, then in the future,
the 2 breeds could be considered separate species!
Long & Slichter