Parents across a wide range of animal groups modify the environments in which their offspring develop. Such modifications are a central aspect of what is known as developmental niche construction: parents shape the conditions under which their offspring grow and, in doing so, alter the selection pressures acting upon them. In the burying beetle (Nicrophorus vespilloides), parents prepare the carcass on which their larvae develop by removing fur or feathers and applying antimicrobial secretions.
“Although developmental niche construction is of considerable theoretical importance, it is often studied only under simplified conditions or with a focus on individual aspects of parental care. As a result, it frequently remains unclear how different parental modifications interact in ecologically relevant contexts,” says Eric Grubmüller, doctoral researcher at the Evolutionary Animal Ecology research group at the University of Bayreuth and first author of the study.
To better understand these interactions, the researchers combined laboratory and field experiments. First, they compared the survival and growth of larvae raised on parent-prepared carcasses with those raised on unprepared carcasses. They also analysed the volatile compounds emitted by the carcasses.
“Our results show that larvae raised on prepared carcasses have higher survival rates and achieve greater growth than larvae raised on unprepared carcasses. At the same time, parental preparation alters the composition of the carcass’s odour profile,” says Prof. Dr. Sandra Steiger, Chair of Evolutionary Animal Ecology at the University of Bayreuth.
In nature, carcasses are a valuable and fiercely contested resource. In a field experiment, the researchers demonstrated that the altered odour profile of prepared carcasses makes them less attractive to competitors: prepared carcasses were visited significantly less often by competing insects than unprepared carcasses. In addition, parental secretions influence the microbial community on the carcass. The study shows that parental care can buffer differences arising from varying soil conditions. This creates a more stable microbial environment, which in turn reduces larval mortality.
Comparison with a Related Species Provides Evidence for Evolutionary Dependence
The beetle species Ptomascopus morio is closely related to burying beetles. However, unlike Nicrophorus vespilloides, parents of this species do not prepare carcasses before their larvae hatch. In a further experiment, larvae of P. morio survived equally well on both unprepared carcasses and experimentally provided prepared carcasses. By contrast, larvae of the burying beetle showed lower survival rates when raised on unprepared carcasses.
“This difference supports the hypothesis that larvae of the burying beetle have become evolutionarily adapted to a developmental environment created by their parents,” explains Steiger. The enhanced survival associated with parental care may have generated an evolutionary feedback loop. Because parental care provides larvae with a protected environment, they are less exposed to harmful microbes and competing insects. Over many generations, traits can evolve that are specifically adapted to these protected conditions, thereby increasing offspring dependence on parental care. In other words, parental care may create conditions that, in the long term, lead to a need for even more parental care.
The study was funded by the German Research Foundation (DFG) (STE 1874/6-3, project number 277139873).
