The Evolutionary Dynamics of Gynodioecy inLobelia

Abstract

Premise of research. Plant mitochondria are expected to show no within-species haplotype diversity. However, sex is determined in some plants by an interaction between mitochondrial cytoplasmic male sterility (CMS) genes and nuclear restorers, resulting in gynodioecy. A question arises as to whether CMS genes are transient or under balancing selection. With balancing selection, rare CMS genes should be favored, potentially resulting in the maintenance of multiple mitochondrial haplotypes. Given that populations with multiple CMS genes are expected to have higher proportions of females, we predicted that the percentage of females in a population would be positively correlated with mitochondrial haplotype diversity.Methodology. We compared sequence diversity in regions of the mitochondrial cob and cox1 genes for populations of multiple species of Lobelia, which includes hermaphroditic and gynodioecious members.Pivotal results. Sequence variation was low, with haplotypes across five North American species va...