Biparental care is a resilient evolutionarily strategy persisting across multiple species of small carpenter bees despite low paternity

Biparental care is rare in insects and is commonly attributed to genetic monogamy, which yields high fitness benefits for caring males. The discovery of biparental care despite low male paternity in the bee Ceratina nigrolabiata challenges this view. We tested whether this pattern is population-specific or evolutionarily stable by examining the frequency of biparental care and male paternity in two additional populations of C. nigrolabiata and three closely related species. Biparental care occurred in all studied populations and species, although at varying frequencies. Guarding males exhibited low paternity due to female multiple mating. These results indicate that biparental care can persist over evolutionary timescales (ca. 5–8 million years) even under low paternity, suggesting that mate guarding may be a key selective force promoting its evolution.