BACKUP SYSTEM. “Hermaphrodites can mate with each other and benefit from the advantages of sex by mixing their genomes, but when mates are difficult to find, hermaphrodites can also escape the need for a reproductive partner by self-fertilization (which, however, may produce low-fitness offspring due to “inbreeding depression.”
http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1001899