On the phenotypes of independently feral populations
Biologists since Darwin have predicted that feral phenotypes will revert
from domestic to wildtype forms across generations, and observed that
admixture between domestic breeds can produce such reversions rapidly
(Li and Liu 2014). Observations from both Hawaii and Bermuda feral
chickens support this general prediction, despite these populations’
colonization of islands separated by ~9000km linear
distance in the Pacific and Atlantic oceans. Among the traits comprising
a shared putative “feralisation syndrome” are reduced body mass and
comb size (as seen in Red Junglefowl), and plumage colour and patterning
that resemble the Red Junglefowl’s to varying degrees. In a similar
manner to domestication, there is the potential that feralisation is
driven by a distinct set of alleles that are common between distinct
populations. However, even with the commonality of this feralisation
syndrome, certain heritable, domestication-related phenotypes were
observed in Bermudian chickens, but not Hawaiian chickens. These include
polydactyly (additional toes), yellow leg-skin, and comb variants (e.g.
rose and duplex combs (see Table 2)).