The detection of brood parasitism and quasi-parasitism in the burying beetle Nicrophorus quadripunctatus under natural conditions

Intraspecific brood parasitism (IBP), where a parasitic female lays eggs in the nest of another female of the same species, occurs in insects and birds. Also, quasi-parasitism (QP), where a parasitic female copulates with a host male at his nest and lays eggs that are fertilized by the male, has been documented in a few monogamous birds, but QP has not been observed in any insects. Burying beetles, genus Nicrophorus, use small vertebrate carcasses for reproducing and providing biparental care for their offspring. IBP has been observed in one burying beetle by laboratory experiments, but has not been well reported under natural conditions. IBP and QP may occur under natural conditions in burying beetles. Here we focused on a burying beetle, Nicrophorus quadripunctatus. Ten broods, consisting of larvae and their parental female and male, were collected from a deciduous forest. To investigate the kin relationship between parents and larvae, eight microsatellite DNA loci were used. We detected three types of parasitic larvae: 1) larva not related to either its parental female or male, 2) larva not related to its parental female, but unknown regarding its parental male, and 3) larva not related to its parental female, but related to its parental male. These results suggested that IBP and QP can occur with certain frequencies in the reproduction of N. quadripunctatus under natural conditions. QP is thought to have a benefit for a parental male to enhance his paternity within one brood in this species.