Biparental care improves major male paternity in a burying beetle, testing a hypothesis of paternity assurance

Biparental care of offspring is present but rare across the animal kingdom and has been postulated as a beneficial strategy that increases the number of offspring that can be raised. However, paternity assurance is generally doubtful compared to maternity; polyandrous broods, high rate of extra‐pair matings and sperm competition lead to less certain paternity, and this uncertainty of paternity would incline males to desertion from biparental care. Therefore, high paternity assurance should favour the evolution of paternal care of offspring. Paternity was estimated using two methods: the pedigree method and the pairwise method. We compared paternity between the broods of uniparental (female) and biparental care in a semi‐natural setting using co‐dominant markers, microsatellite DNA markers, in the burying beetle Nicrophorus quadripunctatus (Coleoptera: Staphylinidae: Silphini). Parentage analysis using the pedigree method showed that paternity of the putative major males (i.e., the proportion of larvae sired by the first dominant father per brood) was significantly higher in biparental care broods than in uniparental care broods (mean ± SD = 0.81 ± 0.20 for biparental care and 0.67 ± 0.17 for uniparental care). Consistent with this result, the pairwise method also showed that paternity of resident males (sampled males) was significantly higher in biparental broods than in uniparental broods. Biparental care of N. quadripunctatus can limit extra‐pair copulation but may not limit the paternity of their own. Biparental care can function as a behavioural mechanism of paternity assurance, suggesting that cooperation between males and females may evolve not only for offspring survival but also to secure reproductive success under conditions of uncertain paternity.