| Summary: | The ‘modern evolutionary synthesis’ emphasised the role of genetic inheritance in driving natural selection; however, this is not the only means by which biological changes may be passed on to future generations. Information can also be transmitted non-genetically, and this could be an important agent of evolution. Non-genetic information can be acquired in two different ways: it can be inherited from parents (for example, through maternal and paternal effects) or gathered from the environment. Transmission of information in this manner can result in durable changes in behaviour, which allow for adaptation to variable conditions, and might ultimately bring about adaptive divergence. To investigate non-genetic transmission of information between parents and offspring, I studied the effects of being reared in the presence of an aversive stimulus, peppermint extract, on the fruit fly Drosophila melanogaster using a range of behavioural assays. The results demonstrate that naïve flies exposed to peppermint found it aversive, with exposure substantially reducing their survival; however, the offspring of flies reared in the presence of peppermint showed a significantly reduced aversion despite having no previous direct contact with the stimulus. This strongly suggests that a transmission of information (relating to preference for peppermint) has occurred from parents to offspring. This effect was preserved for four generations if the peppermint stimulus was removed from the food source after only one generation, but with continued exposure to peppermint the reduction in aversion was sustained, and a preference for peppermint may even have developed. Mutant flies lacking OrCo, Trp and Painless showed abnormal behavioural responses to peppermint, suggesting that these genes may be involved in detecting and/or responding to this aversive stimulus. These experiments demonstrate that environmental changes (i.e. the introduction of an aversive stimulus) can instigate biological modifications in D. melanogaster that are passed on non-genetically to future generations. This is most likely true for other insects and animals more generally, and further studies of additional model and non-model species will help to demonstrate the importance and prevalence of non-genetic transmission of information as a driver of fundamental evolutionary change.
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