More junk makes for better dads.

Prairie vole dads are models of dedicated fatherhood. Even among them, however, some dads are more exemplary than others. Now, a new molecules-to-behavior analysis links particularly dutiful fatherhood in these hamster-size rodents to a stretch of DNA that scientists once dismissed as meaningless junk.

Two closely related species of voles intrigue biologists because the voles live such different lives. Prairie voles bond into couples and share pup care. In meadow voles, males mate with various females and don't provide care for the pups.

Earlier research tied the prairie vole's paternal devotion to a long stretch of repeated DNA snippets near a gene linked to detecting the hormone vasopressin. This hormone affects family behavior in voles. Meadow voles come up short in this snippet count.

Now, Elizabeth Hammock and Larry Young of Emory University's Yerkes National Primate Research Center in Atlanta report on snippet variations within the prairie vole species itself. In specially bred lines of prairie voles, the researchers found that males with an especially long string of repeated DNA in the critical region spent more time with their mates and pups than did males with shorter strings.

Numbers of such snippets, also called DNA microsatellites, can change quickly over generations (SN: 12/18/04, p. 387). Thus, they could contribute to rapid evolution, the researchers note in the June 10 Science.--S.M.