Compensation-Draft Feedback
The co-evolution of mt and N genes has been proposed to lead to rapid
serial fixation of alleles if a positive feedback loop arises as a
consequence of changes and counter-changes between coevolving mt and
N-mt genes. This idea is called the compensation-draft feedback
hypothesis (Oliveira et al. 2008). Compensatory coevolution describes a
situation whereby co-functioning sets of mt and N-mt genes are each
under strong selection to improve aspects of performance that arise from
the products of the other genome (Hill 2020). For instance, it was
experimentally demonstrated that in a lab population of nematodes that
the mt genome rapidly evolved a novel genotype to compensate for an
OXPHOS dysfunction created by a N-mt allele (Christy et al. 2017). This
example involves the interaction of protein-coding genes in an
experimental lab setting, but for the reasons stated above, in most
natural populations, the interacting mt and N gene products may be
involved in transcription, translation, and replication of mt genes. The
rapid fixation of mt genomes that carried this single adaptive
nucleotide change might also have led to fixation of slightly
deleterious alleles that happened to be associated with that allele. By
this process of compensation-draft feedback, selective sweeps fix one
problem while creating future problems that can be fixed through further
selective sweeps when solutions happen to evolve. Such a series of
selective sweeps would perpetually suppress with-population variation in
mt genotypes while rapidly generating unique mt nucleotide sequences
among populations thereby giving rise to mt DNA barcode gaps.