I think there are two comparisons being compared in this example with one comparison being shrimp vs. shrimp (which makes this example a little confusing because of the wording).

I think this example could have been easier to understand if it were with another animal/species.

Ex. The genetic differences between the canine population and are much less significant than those between canines and any other mammal.

We know a golden retriever and pomeranian are still much more genetically similar than that of a cat and a Pomeranian. Same goes for any other mammal and our example canines.

I don't know if that helps.