The role of genomic balance in accumulating species hybrid incompatibilities is discussed. Aneuploidy has been shown to produce more global modulations than polyploidy with the responsible genes being transcription factors and signaling components involved in molecular complexes, illustrating a stoichiometric component to gene expression. Genomic imbalance is usually detrimental to the organism and in many cases results in lethality. Here, it is proposed that once gene flow is prevented between or within populations by various speciation initiating processes, the stoichiometric relationship of members of macromolecular complexes can change via compensatory drift with the eventual result of newly established functional balances. However, when these new relationships are brought together in interspecific hybrids, detrimental consequences will occur. We suggest that these detrimental interactions contribute to hybrid incompatibilities.
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