Finally, in stabilizing selection there is selection against extreme trait values on both ends, which causes a decrease in variance around the average value and less diversity.
Stabilizing selection, if ubiquitously spread across the network, could then be a wall that makes the formation of novel interactions more difficult and maintains previously established interactions.
Those elements that are responsible for similarities between different species should be conserved through time (stabilizing selection), while those elements responsible for differences among species should be divergent (positive selection).