Molecular ageing by measuring DNA methylation: a new tool for bat conservation

Age-structure is one of the fundamental parameters affecting the conservation status of populations. Such information is highly valued in wildlife conservation yet it is exceptionally difficult to measure, and the only recognised methods are very time consuming. Here, I assessed the use of DNA methylation of homologous genes as a novel way of establishing the age structure of a rare and elusive wild mammal: the Bechstein's bat, Myotis bechsteinii. I collected 62 wing punches from individuals whose ages were known as a result of a long-term banding study. DNA methylation was measured at seven CpG sites from three genes which have previously shown age-associated changes in humans and laboratory mice. All CpG sites from the tested genes showed a significant relationship between DNA methylation and age, both individually and in combination (multiple linear regression R2=0.58, p<0.001). This method is of considerable practical benefit as it can reliably age individual bats. It is also much faster than traditional capture-mark-recapture techniques, with information on the age structure of an entire colony being available from a single sampling session, facilitating prompt conservation action when required. By identifying three genes which can provide useful epigenetic data across distantly related species, this study also suggests that the techniques can potentially be applied across a wide range of mammals.