Cryptic Speciation of the Oriental Greenfinch on Oceanic Islands.

The Oriental greenfinch, , is a small seed-eating finch that breeds in the eastern Palearctic region, an area that spans from Russia in the east to China, Korea, and Japan in the south and southwest. Several subspecies have been described based on subtle morphological characteristics, although the taxonomy varies among different authors. Although many ecological studies have been performed, there has been no phylogenetic study that encompasses the species' entire geographical range. We used four regions of mitochondrial DNA to analyze the intraspecies genetic phylogeny and diversity of the Oriental greenfinch. In addition, we performed morphometric analyses using museum specimens. Genetic analysis identified two clades that diverged approximately 1.06 million years ago. These were a population from the Ogasawara Islands, Japan (subspecies , Clade B), and the other populations (Clade A, which could not be subdivided according to geographic context). Morphometric analyses showed that the population on the Kuril Islands (subspecies ) had the longest mean wing length, whereas had the shortest wings. also had the longest mean bill length, probably because it has adapted to feeding on the Ogasawara Islands. Based on molecular phylogeny and morphology analyses, we recommend that should be treated as a completely distinct species, called the Ogasawara greenfinch, . It is critically endangered and needs to be specially protected.