While the contour tree does not take the spatial locations of the input samples into account, we would expect to see repeating patterns of saddle and extrema due to the periodic behavior of the Ackley function. One can see some of this, for example, in the upper part of the graph where we can see similar-looking 3 branch tree structures. However, without knowing beforehand that these patterns exist it is not easy to understand what these repeating patterns mean.