Yes you do, because according to evolution all species continue to mutate and change. You guys cannot have it both ways - either evolution is false or the studies are false. Species cannot both be mutating and in a state of stasis. This is the problem with evolutionists, constant doubletalk and circular reasoning.
Here's the sentence you appearently missed: "The difference will be accounted for by changes in BOTH species over that time." If I find that two species share a good deal of DNA I can surmise that they split off from each other at some point. These species will also have some DNA that is different and I could further surmise that this is because both species experienced change while isolated from one another.
Actually they can. Picture species not as a monolithic block, but as a cloud of individuals centered about a norm, the norm being the best adaptation to the particular environment of the species. The fringes of the cloud are the mutations that crop up ever generation. As they are farther from the norm, they have a decreased chance of surviving to propogate (it doesn't mean they won't surive, just that their chances are diminished). Hence, we have a species in stasis and mutating at the same time.
Now, suddenly, the environment changes and the norm moves in one direction or another. Those mutations that were on the fringe in that direction are now closer to the new norm, and their chances of survival have increased. The former center of the cloud is now the fringe and the fringe on the opposite side has become untenable and will likely die off. Eventually the species will cluster about the new norm, having evolved through the process of mutation (the fringes) and natural selection (the clustering about the norm).
Sometimes a group of this cloud will become isolated by some mechanism (a land bridge springs up, mountains arise, continents split) and your former cloud becomes two new clouds, each clustered about its own norm, and each free to move in completely different directions if the need arises. Hence we have speciation.
Now, none of the above is in any manner "double talk." It is clear, concise, and fairly accurate for the discussion at hand. Of course, I'm not holding my breath that you'll accept it as such and discuss it on its merits, and I'm fully prepared for you to simply dismiss this out of hand with one of your "liar evolutionist" comments.