Nuclear-mitochondrial conflict in the bladder campion Silene vulgaris. Populations of gynodiecious plants such as S. vulgaris consist of females (pictured here) and hermaphrodites, the latter producing both seeds and pollen [24, 26]. Females are produced from hermaphrodites by mitochondrial variants that interfere with the development of the stamens, called cytoplasmic male sterility (CMS). Because they are primarily transmitted through ovules but not pollen, the mitochondria gain a fitness advantage from reducing allocation to male reproduction. CMS variants, however, are often subject to counter-evolutionary changes in nuclear-encoded genes that suppress their effects and restore male fertility. Photo courtesy of Doug Taylor, University of Virginia.