There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.
Abstract
<p class="first" id="P1">The study of reproductive isolation and species barriers
frequently focuses on mitochondrial
genomes and has produced two alternative and almost diametrically opposed narratives.
On one hand, mtDNA may be at the forefront of speciation events, with coevolved mitonuclear
interactions responsible for some of the earliest genetic incompatibilities arising
among isolated populations. On the other hand, there are numerous cases of introgression
of mtDNA across species boundaries even when nuclear gene flow is restricted. We argue
that these seemingly contradictory patterns can result from a single underlying cause.
Specifically, the accumulation of deleterious mutations in mtDNA creates a problem
with two alternative evolutionary solutions. In some cases, compensatory or epistatic
changes in the nuclear genome may ameliorate the effects of mitochondrial mutations,
thereby establishing coadapted mitonuclear genotypes within populations and forming
the basis of reproductive incompatibilities between populations. Alternatively, populations
with high mitochondrial mutation loads may be rescued by replacement with a more fit,
foreign mitochondrial haplotype. Coupled with many non-adaptive mechanisms of introgression
that can preferentially affect cytoplasmic genomes, this form of adaptive introgression
may contribute to the widespread discordance between mitochondrial and nuclear genealogies.
Here, we review recent advances related to mitochondrial introgression and mitonuclear
incompatibilities, including the potential for cointrogression of mtDNA and interacting
nuclear genes. We also address an emerging controversy over the classic assumption
that selection on mitochondrial genomes is inefficient and discuss the mechanisms
that lead lineages down alternative evolutionary paths in response to mitochondrial
mutation accumulation.
</p>