Before revision:  In order to explore the solely and fundamental effect of the clustering  , we employ a minimal model where no game is involved and a simple cycle is adopted. In this way, we disentangle the clustering and the games. The applied process reflects very nontrivial effects of the clustering. Our results show the assortment is an amplifier of the selection for the connected mutants compared with the separated ones.
After revision:  In order to explore the solely and fundamental effect of the clustering , we employ a minimal model with frequency independent fitness on a circle. It disentangles the clustering of mutants from game dynamics. The distance between two mutants on the circle is adopted as a natural indicator for the clustering of mutants or assortment. We find that the assortment is an amplifier of the selection for the connected mutants compared with the separated ones.