Relationship between reproductive mode and mitochondrial diversification inferred by cytonuclear disequilibria in the bark louse Echmepteryx hageni

The bark louse Echmepteryx hageni is a common species in the eastern United States that is parthenogenetic, with only two known, small populations that reproduce sexually.  Previous work has shown that contrary to theoretical expectations, the asexual forms have exceptionally high haplotypic diversity, whereas sexuals have very low haplotypic and nucleotide diversity.  There are three hypotheses that could explain the elevated haplotypic diversity of the asexual relative to sexual populations:  (1) sexuals are derived from the asexuals, (2) asexual E. hageni have a higher mutation rate, and (3) conversion of a genetically diverse species from sexual to primarily asexual reproduction.  A defining difference among the hypotheses is whether haplotype diversification took place during a period of sexual or asexual reproduction. We use measures of cytonuclear disequilibrium between multiple SNP loci and mitochondrial haplotypes to infer the mode of reproduction during mitochondrial diversification.