The effect of the social environment on the parental care and offspring performance of burying beetles, Nicrophorus vespilloides.
Box Power, Olivia
Thesis or dissertation
University of Exeter
Reason for embargo
I wish to publish papers using material that is substantially drawn from my thesis.
This thesis details two experiments on burying beetles, Nicrophorus vespilloides, examining the evolutionary consequences of different elements of the social environment for parental care and offspring performance. The first experiment (Chapter 2) followed on from a previous study which found that, under biparental conditions, females burying beetles from lines selected for a high mating rate provide less parental care and have lower offspring performance than those from a low mating rate line. This suggested that selection on females in the high mating rate line due to the costs of mating lead to the evolution of a reduction in their parental care. In contrast, selection on mating rate had no effect on male parental care, suggesting the costs to a high mating rate are greater for females than males. Male and female burying beetles in the wild also commonly display uniparental care, where they care for their larvae in the absence of a partner. Chapter 2 investigated whether the costs to a high mating rate for parental care are also greater for females than males under uniparental conditions. The results of the experiment suggest that the costs of a high mating rate are indeed higher for females than males under uniparental conditions. Few studies have investigated the impact of the social environment on parental care across different non-social environments. The other aim of this experiment was to investigate whether the impact of a high mating rate (social environment) on parental behaviour was dependent upon the non-social environment (carcass size). This is important because, if this is the case, the evolution of plasticity in parental care in response to the social environment will be heavily impacted by the non-social environment experienced (e.g. resource availability). The size of the carcass on which burying beetles breed is an important element of their non-social environment, as it has a large impact on the number of larvae that can be raised and on larval mass. Costs of a high mating rate on the number of larvae initially produced and the proportion of larvae surviving to dispersal were found to be greater when breeding on a large carcass, suggesting high mating rate line individuals are unable to take advantage of the extra resources available. 3 Few studies have investigated the impact of female-female competition for resources on the expression of parental care, especially in species other than mammals. One of the reasons that female-female competition has received little attention is that it was perceived to be of less evolutionary significance than male-competition, as in many species males show more aggression and have more elaborate ornaments and weapons. However, in recent years the significance of female-female competition for female fitness has become more appreciated. The second experiment in this thesis (Chapter 3) investigated the impact of the presence of a rival female prior to reproduction on female parental care and offspring performance. An earlier study had found that female burying beetles that experience competition increase their expression of parental care. I therefore predicted in my study that females may be able to alter the phenotype of their offspring to best match them to the competition environment they are likely to experience. My study differed from the previous study by using beetles from genetically diverged selection lines. This enabled me to investigate whether there is a genetic variability for this plasticity in parental care behaviour (a GxE) in response to the social environment. Whether there is a GXE for plasticity in behaviour has important implications for the speed at which the extent of plasticity will evolve in response to selection. The results of my experiment showed that females that experienced a rival produced heavier offspring. This is potentially an example of an anticipatory parental effect, as heavier larvae are expected as adults to be better able to compete for access to a carcass. There was no GxE for plasticity in parental care behaviours, suggesting that the extent of plasticity of parental care behaviours may not evolve quickly in response to selection, such as due to climate change.
MbyRes in Biological Sciences