Feralisation - The Understudied Counterpoint to Domestication

Feralisation is a complex process that occurs when a domestic population is returned to the wild. It impacts species invasion biology, speciation, conservation and hybridisation and can be thought of as the reverse of domestication. Domestication has been an area of intense interest and study ever since Darwin, and useful as a model for evolution and the effects of strong directional selection. Despite domestication being used to identify genes affecting a large number of traits that change with selection, little is known about the genomic changes associated with feralisation. Much of the current work on the genetics of feralisation has focused on the detection of early hybrids (F ₁ or F ₂ ) between wild and domestic populations. Feralisation can lead to large changes in morphology, behaviour and many other traits, with the process of feralisation involving the sudden return of both natural and sexual selection. Such evolutionary forces influence predatory, foraging and mate choice decisions and exert strong effects on once domesticated, now feral, individuals. As such, feralisation provides a unique opportunity to observe the genomic and phenotypic responses to selection from a known (domesticated) standpoint and identify the genes underlying these selective targets. In this review, we summarise what is known in particular regarding the genomics of feralisation, and also the changes that feralisation has induced on brain size and behaviour.