Population genomic, olfactory, dietary, and gut microbiota analyses demonstrate the unique evolutionary trajectory of feral pigs

Domestication is an intriguing evolutionary process. Many domestic
populations are subjected to strong human-mediated selection, and when
some individuals return to the wild, they are again subjected to selective
forces associated with new environments. Generally, these feral
populations evolve into something different from their wild predecessors
and their members typically possess a combination of both wild and human
selected traits.  Feralisation can manifest in different forms on
a spectrum from a wild to a domestic phenotype. This depends on how the
re-wilded domesticated populations can re-adapt to natural environments
based on how much potential and flexibility the ancestral genome retains
after its domestication signature. Whether feralisation leads to
the evolution of new traits that do not exist in the wild or to
convergence with wild forms, however, remains unclear. To address this
question, we performed population genomic, olfactory, dietary, and gut
microbiota analyses on different populations of Sus
scrofa (wild boar, hybrid, feral and several domestic pig
breeds). Porcine Single Nucleotide Polymorphisms (SNPs) analysis shows
that the feral population represents a cluster distinctly separate from
all others. Its members display signatures of past artificial selection,
as demonstrated by values of FST in specific regions of
the genome and bottleneck signature, such as the number and length of runs
of homozygosity. Generalised FST values, re-acquired
olfactory abilities, diet, and gut microbiota variation show current
responses to natural selection. Our results suggest that feral pigs are an
independent evolutionary unit which can persist so long as levels of human
intervention remain unchanged.