A Male Expressed Copulatory Plug Increases Female Fertility in Caenorhabditis Nematodes

The genomes of self-fertilizing hermaphrodites offer a unique opportunity to probe why some genes with sex-specific functions are lost while others are maintained. In the androdiecious species, Caenorhabditis elegans, the presence of mate plugging is polymorphic across genetic backgrounds. The production of a mating plug is controlled by a single gene, plg-1, which has male-specific expression. Given that males are present less than 1% of the time, this gene is likely lost through relaxed selection or purifying selection, especially if mate plugging is maintained through intrasexual selection in males as is often hypothesized. We capitalized on a diverse panel of almost 2,000 C. elegans natu