Nest construction and its effect on posthatching family life in the burying beetle Nicrophorus vespilloides

Through the effort required to construct them, the microenvironmental conditions they impose on the family and their indirect influence on posthatching care, nests play a key role in influencing family life. We combined experimental evolution with cross-fostering experiments on laboratory populations of Nicrophorus vespilloides to investigate three ways in which the nest can contribute more broadly to parental investment. We used replicate populations of N. vespilloides that had evolved for 42 generations under contrasting regimes of care. Populations were either able to supply posthatching care (‘Full Care’) or prevented from supplying any posthatching care (‘No Care’). Research on these populations has previously shown that the No Care populations evolved to build rounder nests, more rapidly, by Generation 14. Here we found (1) larvae raised by Full Care parents on nests prepared by parents from the No Care population did not attain a higher mass by the end of larval development than larvae in other treatments. However, we did discover that (2) cross-fostering nests between families consistently reduced larval mass, and to a similar extent whether nests were cross-fostered between or within the populations. We suggest that cross-fostering disrupted the chemical environment on and around the nest since we found no evidence that (3) nests mediate interactions between males and females. The duration of paternal care was consistently shorter than the duration of maternal care, and even shorter for males from the No Care populations than males from the Full Care populations. Nevertheless, the duration of male care did not predict variation in duration of female care. In short, although the nest is the substrate for burying beetle family life, we found little evidence that it had evolved divergently in our experimental populations to influence parental investment.