<国立科博専報>琉球列島産イノシシの分類学的考察 Taxonomic Study of the Wild Boar from the Ryukyu Islands, Japan
Although the wild boar of the Ryukyu Islands, Japan, has long been recognized as a local race of Sus scrofa LINNAEUS, 1758,by most of the recent authors, it may be a relict nearly related to the common ancestor of the boars. According to the author's opinion, Sus scrofa itself is a superspecies containing such distinct species as cristatus, scorofa, meridionalis, vittatus, leucomystax and riukiuanus. Each of the last three forms of East Asia undoubtedly belonging to a clade, the vittatus group, is in different stage of phylogenetic sequence and seems to have independent history of expansion of the population in the past. It is most likely that such populations have been reproductively isolated from each other more or less completely and that severe competition for existence may have taken place when they meet in a given area. The present distribution of those species must be a final result of such competitions reflecting the presence of reproductive isolation between them. This is the reason why the author is inclined to erect them as distinct species. The wild boar of the Ryukyu Islands, Sus riukiuanus KURODA, 1924,will be recognized on the following cranial and dental characters : upper length of skull as large as that in a cline of leucomystax TEMMINCK, 1942,from Honshu and Kyushu, Japan, Yc=153.8+4.9Xmm, Sys=15.9mm (X=temperature index), and much smaller than that of vittatus BOIE, 1828,Yc=302.0+2.4Xmm, Sys=19.4mm, which contains populations from Ussuri, Manchuria, Korea, Szechwan, Fukien, Formosa, Johore, Sumatra, Java, etc. Second and third upper molars smaller and simpler, and auditory bulla smaller than those of leucomystax. Naso-premaxillary suture incomplete except in old stage, and condyle and angular portion of mandible less developed. Those characters are most clearly retained in the population of Iriomote Island. The cranial and dental characters of the native domestic pig of Hainan, China, are distinctly in primitive conditions than those of vittatus and leucomystax, but evidently in progressed stage of phylogenetic development than in riukiuanus. The opinion of some authors that riukiuanus may only be a feral domestic pig seems not to be acceptable.
国立科学博物館専報 6, 113-129, 1973