Evolution of the G-matrix on Dynamic Adaptive Landscapes

Abstract Experimental studies show that the G-matrix can be shaped by directional selection, so it is natural to ask whether the directional selection associated with peak movement will have appreciable, long-lasting effects on G. Simulation studies have explored the evolution of a two-trait G-matrix under a variety of peak movement scenarios. For example, when the adaptive peak moves at a constant, moderate rate, genetic variation is enhanced, not diminished, by peak movement. Furthermore, peak movement along a genetic line of least resistance promotes stability of the G-matrix. Thus, the greatest stability of the G-matrix can be expected when the M-matrix, the G-matrix, and the adaptive landscape are in three-way alignment, and the adaptive peak moves in that direction as well. Under these circumstances the G-matrix evolves towards an especially stable cigar shape. Simulation studies have also shown that both peak movement and correlational selection can promote the evolution of modular structure in the P- and G-matrices. Finally, we note that studies of G-matrix response to realistic selection regimes provide a bridge to genomic study of adaptation.