Offspring Dependency Is Not Reflected in the Social Immunity of Three Burying Beetle Species

Offspring dependency on parental care varies significantly across species, often driven by parental food provisioning and protection from predation. However, an often-overlooked factor is protection against pathogens through the exhibition of social immunity. However, if and how parental protection from microbial pressure shapes and scales with offspring dependency remains poorly understood. Here, we investigate both personal and social immunity in three species of Nicrophorus burying beetles—a model system known for elaborate parental care and social immunity. These species differ markedly in their offspring's ability to survive without parental care, ranging from independence to complete dependence on post-hatching care. We measured personal and social immunity in adult female and male beetles before, during, and outside of reproductive bouts. Our results show that species with more dependent offspring do not necessarily invest more heavily in social immunity, whereas reproductive state affected immunity differently across species. These findings emphasize the complexity of parent-offspring coadaptation, and the need for further study of the evolutionary trajectory from facultative to obligate family associations.