Inbreeding reduces the ability of young to exploit high-resource nurseries

Parents of many species create a "nursery" in which young develop, and variation in this environment can influence offspring phenotype and fitness. Recent studies have demonstrated that behavioural interactions within these nurseries may moderate inbreeding depression. However, whether other features of the nursery impact inbreeding depression, either directly or through secondary impacts on behaviour, has been less well studied. Here, I describe two experiments involving the burying beetle, Nicrophorus orbicollis, in which I test (1) whether inbreeding depression is sensitive to the size of the carcass that constitutes the nursery and (2) whether inbreeding and carcass size influence parental care behaviour. In the first experiment, I found that resource abundance in the nursery impacted inbreeding depression in larval mass, a trait that determines adult body size and competitive ability. In low-resource nurseries, inbred and outbred offspring did not differ in mass. However, in high-resource nurseries, inbred larvae were smaller than outbred larvae. This inbreeding-by-environment interaction occurred because the mass of outbred larvae was more responsive to resource abundance than the mass of inbred larvae. Larval survival from dispersal to eclosion exhibited inbreeding depression that was independent of resource abundance. In the second experiment, I found no evidence that the inability of inbred larvae to exploit high-resource nurseries was due to differences in parental behaviour. These results suggest that inbred larvae are less able than outbred larvae to take advantage of high-resource nurseries; however, further work is necessary to uncover the mechanisms generating this inbreeding-by-environment interaction.