Fig. 2

Proposed testable relationship between functional genomic network architecture, network node position, and evolutionary outcomes. SN are subnetworks within the functional genomic network of a population with distinct functions (e.g., metabolic pathways). Standing genetic variation exists within nodes, but depends on their position within the network. Black nodes (H) are essential for organismal function and not likely to accumulate non-synonymous mutations; Grey nodes (I) are functionally connected with many others and constrained in accumulating non-synonymous mutations. White nodes (P) are functionally connected to fewest others and most likely to accumulate non-synonymous mutations. Resulting from this, three evolutionary outcomes can be explained: Rapid adaptation is facilitated in white nodes through their high standing genetic variation. Selection being constrained to operate on these nodes in a specific subnetwork increases the speed of adaptation. Convergent evolution is facilitated through the finite number of networks that are related to specific functions and shared among species through common ancestry. The likelihood of convergent evolution within one subnetwork in response to selection increases through the moderate level of genetic variance, combined with constraint posed by the high number of connections to other nodes. Genic evolution is facilitated through the selection pressure only having an effect in the subnetwork with organismal functions related to it but not in others. Selection is likely to operate on standing genetic variation, which is likely concentrated in white nodes (shown as blue squares). These different processes can explain the coexistence of convergent and divergent (rapid, genic) evolution within the genomes of a population