Coadaptation and conflict, misconception and muddle, in the evolution of genomic imprinting

Abstract

Common misconceptions of the 'parental conflict' theory of genomic imprinting are addressed. Contrary to widespread belief, the theory defines conditions for cooperation as well as conflict in mother-offspring relations. Moreover, conflict between genes of maternal and paternal origin is not the same as conflict between mothers and fathers. In theory, imprinting can evolve either because genes of maternal and paternal origin have divergent interests or because offspring benefit from a phenotypic match, or mismatch, to one or other parent. The latter class of models usually require maintenance of polymorphism at imprinted loci for the maintenance of imprinted expression. The conflict hypothesis does not require maintenance of polymorphism and is therefore a more plausible explanation of evolutionarily conserved imprinting.

Non-conflict theories for the evolution of genomic imprinting

“…Wolf and Hager (2006) argued that genetic variation is ubiquitous, however, and should thus be present at these imprinted loci. The issue of simple population-genetic models of selection depleting variation is by no means confined to models for the evolution of imprinting, but the maintenance of variation would seem to be critical here when its elimination is a potential solution to the problem being investigated (see also Haig, 2014).…”

“…Moreover, it should be recognized that cooperation and co-adaptation can arise from genetic conflict (see also Haig, 2014); the metaphor of genetic conflict does not mean that maternal-fetal conflict is the outcome. As far as we are aware, there has been no mathematical modelling in this area, although it is possible that some extension of the approach of Weisstein and Spencer (2003) that incorporates the benefits to the mother may be applicable.…”

Imprinted gene expression in hybrids: perturbed mechanisms and evolutionary implications

“…This difference in mating system could potentially be relevant with regards to the evolution of genomic imprinting because it should lead to different patterns of intrafamilial conflict. The most widely accepted theory for the evolution of imprinting-the 'conflict hypothesis' (Moore and Haig, 1991)-assumes that competition over maternally provided resources between offspring fathered by different males can favour imprinted expression (Haig, 2013; see also Burt and Trivers, 2008). Hence, difference in mating system could alter patterns of relatedness and change patterns of conflict within families.…”

Mammalian viviparity: a complex niche in the evolution of genomic imprinting

“…Very few publications on genomic imprinting had appeared at the time when parent-offspring conflict was formulated (Haig, 1992) or indeed the theory of parent-offspring co-adaptation (Curley et al, 2004;Wolf and Hager, 2006). Haig (2014) now makes clear 'parental conflict theory defines conditions for co-operation as well as conflict in mother-infant relationships' . With the wealth of knowledge now available for the molecular genetic control of genomic imprinting and the phenotypes this represents, I now feel these theories can be viewed with a more critical eye.…”