Evolutionary change in the construction of the nursery environment when parents are prevented from caring for their young directly

Parental care can be partitioned into traits that involve direct
engagement with offspring and traits that are expressed as an
extended phenotype and influence the developmental environment, such as constructing a nursery. Here, we use experimental
evolution to test whether parents can evolve modifications in
nursery construction when they are experimentally prevented
from supplying care directly to offspring. We exposed replicate
experimental populations of burying beetles (Nicrophorus vespilloides) to different regimes of posthatching care by allowing larvae to develop in the presence (Full Care) or absence of parents
(No Care). After only 13 generations of experimental evolution,
we found an adaptive evolutionary increase in the pace at which
parents in the No Care populations converted a dead body into a
carrion nest for larvae. Cross-fostering experiments further
revealed that No Care larvae performed better on a carrion nest
prepared by No Care parents than did Full Care larvae. We conclude that parents construct the nursery environment in relation
to their effectiveness at supplying care directly, after offspring are
born. When direct care is prevented entirely, they evolve to make
compensatory adjustments to the nursery in which their young
will develop. The rapid evolutionary change observed in our
experiments suggests there is considerable standing genetic variation for parental care traits in natural burying beetle populations—for reasons that remain unclear.