Using Experimental Evolution to Study Adaptations for Life within the Family

Abstract

Parents of many species provision their young, and the extent of parental provisioning constitutes a major component of the offspring's social environment. Thus, a change in parental provisioning can alter selection on offspring, resulting in the coevolution of parental and offspring traits. Although this reasoning is central to our evolutionary understanding of family life, there is little direct evidence that selection by parents causes evolutionary change in their offspring. Here we use experimental evolution to examine how populations of burying beetles adapt to a change in posthatching parental provisioning. We measured the performance of larvae descended from lab populations that had been maintained with and without posthatching parental care (Full Care and No Care populations). We found that adaptation to the absence of posthatching care led to rapid and consistent changes in larval survival in the absence of care. Specifically, larvae from No Care populations had higher survival in the absence of care than larvae from Full Care populations. Other measures of larval performance, such as the ability of larvae to consume a breeding carcass and larval mass at dispersal, did not differ between the Full Care and No Care populations. Nevertheless, our results show that populations can adapt rapidly to a change in the extent of parental care and that experimental evolution can be used to study such adaptation.

A limit on the extent to which increased egg size can compensate for a poor postnatal environment revealed experimentally in the burying beetle, Nicrophorus vespilloides

“…These pairs were mated as described above; however, we used smaller carcasses (10–16 g) to be consistent with our previous work (Schrader et al. 2015a,b). Fifty‐three hours after pairing these individuals, we removed the parents and counted the number of eggs that had been laid in the soil (clutch size).…”

“…However, there are key differences between the protocol for removing postnatal care in our long‐term evolution experiments (Schrader et al. 2015a) and that used by Monteith et al. (2012a), which make the environment experienced by larvae immediately after hatching in our experiments far harsher than that experienced by larvae in the work by Monteith et al.…”

“…As part of this work, we have recently shown that laboratory populations of N. vespilloides adapt to experimentally altered regimes of posthatching care: populations raised without posthatching care for generation after generation evolved to fare better in this environment than populations where parental care is present after hatching (Schrader et al. 2015a). …”

“…2015a). The ideal test of this hypothesis would involve directly measuring the relationship between egg size and breeding success under the same “no care” environment used in our previous study (Schrader et al.…”

“…The ideal test of this hypothesis would involve directly measuring the relationship between egg size and breeding success under the same “no care” environment used in our previous study (Schrader et al. 2015a). Unfortunately, this is not possible, as measuring individual eggs requires searching through the soil for eggs, removing the eggs, and then measuring them (either weighing them or photographing them to make linear measurements).…”