Discussion:
A mounting body of work has suggested that mitonuclear incompatibilities
are among the first genetic barriers to evolve at early stages of
population divergence across taxa (Burton & Barreto 2012; Burtonet al. 2013; Hill 2016; Sloan et al. 2017; 2018; Hillet al. 2018), affecting multiple life history traits that render
hybrids unfit. Nevertheless, it is still unclear whether such BDMIs
involve a few nuclear regions in a localized part of the genome, or if
they involve many regions throughout the nuclear genome. Understanding
the genetic architecture of mitonuclear incompatibilities can benefit
from the “evolve-and-resequence” approach developed for model
organisms (Burke et al. 2014; Schlotterer et al. 2015),
where adaptation to divergent environments stems from standing genetic
variation generated from an initial hybrid population. In this study, we
evolved sickly F2 hybrids of the copepod Tigriopus californicus ,
where parental nuclear alleles are represented at similar frequencies,
and monitor change in these allele frequencies after experimental
evolution under two divergent mitochondrial backgrounds. We hypothesize
that recovery of hybrid fitness will primarily result from selection
favoring mitonuclear compatibility and that allelic frequency changes
across the genome will reveal locations where such selection has acted.