Genomic evolution of island birds from the view of the Swinhoe's pheasant (Lophura swinhoii).

Island endemic birds account for the majority of extinct vertebrates in the past few centuries. To date, the evolutionary characteristics of island endemic bird's is poorly known. In this research, we de novo assembled a high-quality chromosome-level reference genome for the Swinhoe's pheasant, which is a typical endemic island bird. Results of collinearity tests suggest rapid ancient chromosome rearrangement that may have contributed to the initial species radiation within Phasianidae, and a role for the insertions of CR1 transposable elements in rearranging chromosomes in Phasianidae. During the evolution of the Swinhoe's pheasant, natural selection positively selected genes involved in fecundity and body size functions, at both the species and population levels, which reflect genetic variation associated with island adaptation. We further tested for variation in population genomic traits between the Swinhoe's pheasant and its phylogenetically closely related mainland relative the silver pheasant, and found higher levels of genetic drift and inbreeding in the Swinhoe's pheasant genome. Divergent demographic histories of insular and mainland bird species during the last glacial period may reflect the differing impact of insular and continental climates on the evolution of species. Our research interprets the natural history and population genetic characteristics of the insular endemic bird the Swinhoe's pheasant, at a genome-wide scale, provides a broader perspective on insular speciation, and adaptive evolution and contributes to the genetic conservation of island endemic birds.