Meeting Abstract
Cytonuclear linkage disequilibrium (LD) is the non-random association of alleles between nuclear and cytoplasmic genomes (ptDNA or mtDNA). Patterns of cytonuclear LD can indicate admixture of divergent populations, cytonuclear selection, non-traditional organellar inheritance, or the occurrence of more than one type of mtDNA or ptDNA within an individual (heteroplasmy). Gynodioecious plant species are known to exhibit biparental inheritance of organelles, creating heteroplasmy. We used the gynodioecious plant species, Daucus carota, or wild carrot, to investigate cytonuclear LD. We genotyped 265 individuals from two North American regions, 136 from the Olympic Peninsula, Washington State and 129 from Nantucket Island, Massachusetts. We used 15 nuclear microsatellites, one SNP and one insertion-deletion (indel) located in the mtDNA, and one indel located in the ptDNA to calculate nuclear-nuclear LD, cytonuclear LD, and LD between each pair of organellar loci. We were further able to identify over 100 individuals heteroplasmic for one of the mitochondrial SNPs and over 30 individuals heteroplasmic for the plastid indel. Thus, we were able to calculate the same sets of cytonuclear LD values for individuals that are heteroplasmic and homoplasmic (non-heteroplasmic) for the mitochondrial SNP and plastid indel. When considering heteroplasmy or homoplasmy as the cytotype, no non-random associations were found, and LD values were low. However, when considering the SNP or indel variant as the cytotype, differences were found in the LD values between heteroplasmic and homoplasmic groups. In particular, the range of LD values increased when found in the heteroplasmic state.
