Sex in time

So imagine the edge of a huge lake, where, for whatever reason, the original community of animals tended to move clockwise. Let's say there's a hill that ends in sharp drop just where the dark gray meets the bright white line, above. So, we have a species breeding at the bright white spot, and as it moves around the lake small, local changes occur. Longer / shorter legs, variations in coloration, and so on, but all [obviously] just a slight genetic difference on average from the animals next door. At every point in the circle, a community is basically indistinguishable from its immediate neighbors, and any individual could belong to either of its neighboring groups. Interbreeding is not a problem, and can extend in both directions some way beyond the neighbors. In practical terms, for creatures of a small size and with a lake of a large size - interbreeding occurs without limits.

But stepping back and looking at the image as a whole, by the time the circle is complete the last two neighboring communities, on either side of the hill / cliff, are quite distinct - different species, despite the fact they are connected by an unbroken chain of communities who can happily mix and breed with their neighbors. This is why the idea of 'species' is not as simple as it seems, either at a point in time, or, more to my purpose, over a very long period of time

My purpose is that if all the 'species' ever extant where brought back to life there could be one unbroken chain of fucking going right back to the first creatures that invented sex. I don't know what to do with this idea, but it seems to be a passion killer.