Detection of extra‐pair maternity in a carrion beetle under natural conditions

The provision of care to offspring is a costly endeavour that can be hijacked by others—known as brood parasitism. Females can choose to lay eggs in the nest of a conspecific female, resulting in extra‐pair maternity (EPM). Burying beetles of the genus Nicrophorus use small vertebrate carcasses for reproduction and provide biparental care to their offspring. Carcasses are a rare resource; thus, competition often occurs among adults of the same sex. A previous study examined the outcomes of competition and subsequent parental care of Nicrophorus vespilloides using laboratory experiments. Larvae of losing females were sometimes cared for by the winning females, which is generally an evidence of EPM. However, the presence of EPM in burying beetles under natural conditions has not yet been well established. Here, we focused on the reproduction of N. quadripunctatus in the field. To examine the presence of EPM, maternity analysis was performed on 149 offspring and their caring females in 10 broods, using 8 microsatellite DNA loci. Seven larvae originating from three broods were unrelated to their caring females. There were one to three unrelated larvae in each of the three broods. Thus, EPM occurs in N. quadripunctatus reproduction under natural conditions. Here, we tested whether extra‐pair maternity occurs in the parental care of N. quadripunctatus in the field using parentage analyses with eight microsatellite DNA loci. Of 149 offspring from 10 families collected in a deciduous forest, 7 offspring from 3 families were unrelated to their caring females. This study demonstrates the presence of extra‐pair maternity in this species under natural conditions, consistent with the previous results for other Nicrophorus species.