| dc.description.abstract | 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. | en_GB |
