Environmentally induced variation in DNA methylation and embryonic heart rate in Australian birds

The environment is profound in its ability to influence phenotypic variation, and this is a necessary condition for integrating the developing organism into its particular habitat. While phenotypic plasticity is well engrained in ecological research, the underlying processes that mediate its effects remain unclear. Recently, epigenetic and metabolic mechanisms have been proposed to provide an avenue through which early environmental conditions can modulate phenotypic variation. However, before these mechanisms can be implicated in translating environmental effects to the phenotype, it must first be clarified whether epigenetic and metabolic processes are sensitive to environmental variation at all. Here, I examined how DNA methylation and metabolic rate are affected by various abiotic and biotic stimuli in two species of Australian birds. I used MS-AFLP to examine population-wide, and condition dependent patterns of DNA methylation in invasive house sparrows (Passer domesticus) and zebra finches (Taeniopygia guttata), and measured embryonic heart rate (a proxy for metabolic rate) in wild, native zebra finches, to examine environmental effects on metabolism, and the behavioural and developmental consequences of this. The patterns of DNA methylation that were observed in my thesis support the potential for epigenetic marks to respond to prevailing environmental conditions (such as habitat, brood size, invasion history and temperature). Embryonic heart rate measures were also found to be extremely sensitive to a range of environmental stimuli, notably changing in response to temperature and conspecific vocalisations. Embryonic heart rate also correlated with pre-natal developmental rate, however was unrelated to variation in nestling activity levels. Together, the environmentally induced changes described in my thesis support a role for epigenetic and metabolic mechanisms to translate environmental effects to ecologically relevant phenotypic variation. Such phenotypic plasticity could be particularly important for wild populations facing unpredictable and rapid environmental changes.