This cyto-nuclear disequilibrium had already been noticed earlier by Avise et al.[ 12].
Hybrids based on: potential hybrids detected using a) N EWH YBRIDS software, b) diagnostic microsatellite alleles or c) cyto-nuclear disequilibrium.
Third, we identified individuals as hybrids if they were assigned by STRUCTURE to one clade but contained mtDNA from the other (= cyto-nuclear disequilibrium).
Here, cyto-nuclear disequilibrium has been identified in the narrow zone of species overlap in Iceland [ 12, 29, 30, 74, 75], which scales well with a transition zone based on vertebral counts, a nearly diagnostic trait between the two species of eels [ 12, 32].
AF: atrial fibrillation; ANP: atrial natriuretic peptide; APD: action potential duration; GWAS: genome-wide association study; LD: linkage disequilibrium; NPC: nuclear pore complex; OR: odds ratio; SNP: single nucleotide polymorphism.
Also, studies of D. subobscura populations assessing linkage disequilibrium between nuclear markers such as chromosomal inversions or allozymes and mtDNA variability, indicative of selection on mitonuclear genotypes [ 24, 25], found subtle and seemingly transient disequilibria [ 29– 33].
CCL5: C-C motif ligand 5; IκB: inhibitor of NF-κB; IL: interleukin; IPD: invasive pneumococcal disease; LD: linkage disequilibrium; NF: nuclear factor; OR: odds ratio; PCR: polymerase chain reaction; RANTES: 'regulated upon activation normal T cell expressed and secreted'; SNP: single nucleotide polymorphism; TNF: tumour necrosis factor.
As in the previous case involving the Mid-Atlantic Ridge (MAR) mussels, the present example from the eastern Pacific Ocean also exhibits the properties of a Tension Zone: (1) coincident clines at multiple loci; (2) heterozygote deficiencies in the contact zone; and (3) significant gametic disequilibrium among nuclear and cytoplasmic genes.
However, we detected highly significant linkage disequilibrium for 3 nuclear locus-pairs across populations after a sequential Bonferroni correction for k tests (k = 703, p < 7.1 × 10-5): One_MHC2-190 (I = 0.433) and One_MHC2-251 (I = 0.465); One_Tf_ex10-7 (I = 0.632) and One_Tf_ex3-18 (I = 0.084); One_GPDH (I = 0.668) and One_GPDH2 (I = 0.082).
Third, the phenotypic effects of nuDNA and mtDNA x nuDNA seen in our study provides indirect evidence for linkage disequilibrium between mtDNA haplotypes and nuclear genes, as the nuclear genomes were classified based on the mtDNA haplotype with which they were co-expressed in the founding population.
We did not find any evidence of linkage disequilibrium between pairs of nuclear microsatellite markers.
