Pre-hatching care effects offspring dependency in Nicrophorus vespilloides

Parental care is a widespread phenomenon that occurs in many taxa. However, once parental care evolves, offspring in some taxa appear to become increasingly dependent on their parents and family life can become obligatory. Theoretical considerations suggest that coevolutionary processes between parents and offspring during brood care shape offspring dependency. Although the effects of post-hatch care on offspring dependency have been extensively studied, the effects of pre-hatch care characteristics on offspring dependency, particularly in the absence of post-hatch care, remain unclear. To address this gap, we used Nicrophorus vespilloides as a model, a species known for its elaborate biparental care and intermediate larval dependency compared to other Nicrophorus species. We offered 12 N. vespilloides larvae either a carcass prepared by parents of N. vespilloides, N. pustulatus (independent species), or N. orbicollis (highly dependent species) We assessed larval survival and growth after 48 hours and again when the larvae dispersed the carcass for pupation. This allowed us to examine how different characteristics of pre-hatch care provided by different Nicrophorus species along a gradient of larval dependency affect offspring dependency on post-hatch care. We found that N. vespilloides larvae survived and developed best on carcasses prepared by conspecific parents, suggesting species-specific traits during brood care. We also determined the presence and size of feeding cavities that parents of different species opened in the carcasses. The results demonstrate that the mere presence of a feeding cavity, rather than its size, promotes larval survival and growth. Consequently, our data suggest that certain traits of pre-hatch care, such as the timing of opening the feeding cavity, shape larval dependency and thereby might promote the evolution of post-hatch care.