A novel mitochondrial genome of Arborophila and new insight into Arborophila evolutionary history.

The lineage of the Bar-backed Partridge (Arborophila brunneopectus) was investigated to determine the phylogenetic relationships within Arborophila as the species is centrally distributed within an area covered by the distributions of 22 South-east Asian hill partridge species. The complete mitochondrial genome (mitogenome) of A. brunneopectus was determined and compared with four other hill partridge species mitogenomes. NADH subunit genes are radical in hill partridge mitogenomes and contain the most potential positive selective sites around where variable sites are abundant. Together with 44 other mitogenomes of closely related species, we reconstructed highly resolved phylogenetic trees using maximum likelihood (ML) and Bayesian inference (BI) analyses and calculated the divergence and dispersal history of Arborophila using combined datasets composed of their 13-protein coding sequences. Arborophila is reportedly be the oldest group in Phasianidae whose ancestors probably originated in Asia. A. rufipectus shares a closer relationship with A. ardens and A. brunneopectus compared to A. gingica and A. rufogularis, and such relationships were supported and profiled by NADH dehydrogenase subunit 5 (ND5). The intragenus divergence of all five Arborophila species occurred in the Miocene (16.84~5.69 Mya) when there were periods of climate cooling. We propose that these cooling events in the Miocene forced hill partridges from higher to lower altitudes, which led to geographic isolation and speciation. We demonstrated that the apparently deleterious +1 frameshift mutation in NADH dehydrogenase subunit 3 (ND3) found in all Arborophila is an ancient trait that has been eliminated in some younger lineages, such as Passeriformes. It is unclear of the biological advantages of this elimination for the relevant taxa and this requires further investigation.