摘要: Justification of Outstanding Universal Value　　The proposed property is an area that offers outstanding examples of speciation and phylogenetic diversification of terrestrial organisms at various stage

Justification of Outstanding Universal Value

　　The proposed property is an area that offers outstanding examples of speciation and phylogenetic diversification of terrestrial organisms at various stages through varying extents of geographic isolation. Not only have numerous endemic species emerged through relatively recent vicariance events, but also a large number of relict species that have no close relatives on the Japanese mainland or Eurasian Continent occur on this property.

　　Furthermore, because these four islands are located between the tropical and warm–temperate zones, their current fauna and flora include not only representatives of long-standing subtropical lineages but also those of East Asian temperate lineages and South East Asian and Oceanian tropical lineages. Moreover, the high proportion of endemic and threatened species in this area indicates that they deserve a major conservation focus. The proposed property encompasses a set of important, essential habitats for these species.

　　Criterion (ix): The terrestrial organisms occurring in the proposed property likely had broad continental distributions. In the course of the area’s conversion to islands separated from the continent, the terrestrial organisms isolated on each island, with its distinctive environment, have evolved in various unique directions. This has been enhanced by the effects of population fragmentation.

　　In particular, on Amami-Oshima Island, Tokunoshima Island and the northern part of Okinawa Island, a number of terrestrial organisms with limited ability to disperse across the sea, such as non-volant tetrapods, have been isolated from their continental relatives since no later than the Early Pleistocene (between 2 and 1.7 million years ago). This, along with the subsequent extinction of the relatives in surrounding areas, despite the survival of many of the insular representatives to the present because they have been protected from recently emerging predators and competitors, has made the region the centre of relict endemism. Such relict species are generally characterized by prominent geographical and genetic gaps from extant sister populations in other areas. Prominent faunal representatives of such relict endemisms on Amami-Oshima Island, Tokunoshima Island and the northern part of Okinawa Island include the Amami rabbit Pentalagus furnessi; the Long-tailed giant rat Diplothrix legata; three spiny rat species of the genus Tokudaia; the Amami jay Garrulus lidthi; the Black-breasted leaf turtle Geoemyda japonica; Kuroiwa’s ground gecko Goniurosaurus kuroiwae; Anderson’s crocodile newt Echinotriton andersoni; and Namiye’s frog Limnonectes namiyei. Floral representatives include Arisaema heterocephalum (Araceae), Viola amamiana (Violaceae), Polystichum obae (Dryopteridaceae), Platanthera sonoharae (Orchidaceae) and  Solenogyne mikadoi (Asteraceae . The Amami rabbit is estimated to have diverged from the other extant members of the family Leporidae in the Middle Miocene (about 10 million years ago). Since then, it seems to have evolved a suite of distinctive ecological traits while maintaining its largely primitive morphological features. There are no other extant congeners at all, thus making the rabbit endemic to Amami-Oshima Island and Tokunoshima Island at the generic level.

　　On the proposed property, speciations and phyletic divergences are still ongoing at various stages among island populations with close historical affinity. As a result of genetic differentiation in each lineage through geographic isolation caused by insularization of the region, there are numerous cases of between-island in-situ speciation and sub-speciation. Typical example is a group of tip-nosed frogs that has differentiated into four species in this property. Two subspecies of Kuroiwa’s ground geckos are distributed in Tokunoshima Island and the northern part of Okinawa Island. The high frequencies of occurrence of endemic taxa among the amphibians and terrestrial reptiles on the proposed property deserve particular attention. 33 species of endemic terrestrial reptiles and 18 species of endemic amphibians, are found on the four islands. About 121 plant species are endemic to the  four islands.

　　Speciation and further diversification of a number of evolutionary lineages at these islands have therefore supposedly been enhanced. Indeed, many endemic species occur on these islands, most likely as a result of geohistorical processes in the region that involved the initial isolation of insular populations from their continental relatives and subsequently repeated vicariance and secondary sympatry among the former. Moreover, several islands harbour taxa that represent the stage of relict endemism as a result of long insular isolation from the formidable predators or competitors that started to prevail on the continent after the islands became isolated. This is particularly true for Amami-Oshima Island, Tokunoshima Island and the northern part of Okinawa Island in which relict species are particularly frequent because of the islands’ long isolation. These aspects of the proposed property collectively constitute an outstanding example of the effects of long-standing geohistorical processes on speciation and phylogenetic diversification of terrestrial organisms.

　　Fossil evidence indicates that on Amami-Oshima Island, Tokunoshima Island and the northern part of Okinawa Island there have been no, or have long been no endothermic vertebrates such as carnivorous mammals and large-bodied resident birds of prey to occupy the position as the top predators in the indigenous food web. Instead, the biotic community of this region is characterized by a high frequency of relict species (see above) and constitutes a unique food web in which a few large-bodied snakes occupy the top predator position.

　　Criterion (x): The proposed property contains important habitats for a large number of internationally recognized threatened species that are listed on the IUCN Red List. Furthermore, the islands provide diverse instances of neo- and relict endemism that are most explicitly represented by non-volant, inland-water-dependent taxa such as amphibians, the dispersal ability of which across the ocean is very limited by physiological constraint. From the global point of view, therefore, this property can obviously be regarded as among the most important areas for biodiversity conservation.

　　These islands contain irreplaceable habitats for more than 30 terrestrial species listed on the IUCN Red List in the Vulnerable (VU), or higher, threatened categories. These include the Iriomote leopard cat Prionailurus bengalensis iriomotensis (IUCN Red List 2012: critically endangered, CR), Amami rabbit (endangered, EN), Okinawa spiny rat Tokudaia muenninki (CR), Amami spiny rat Tokudaia osimensis (EN), Tokunoshima spiny rat Tokudaia tokunoshimensis (EN),  Long-tailed giant rat (EN), Okinawa rail Gallirallus okinawae (EN), Okinawa woodpecker Dendrocopos noguchii (CR), Amami jay (VU), Black-breasted leaf turtle (EN), Yaeyama yellow-margined box turtle Cuora flavomarginata evelynae (EN), Kuroiwa’s ground gecko (EN), Anderson’s crocodile newt (EN), and Utsunomiya’s frog Odorrana utsunomiyaorum (EN). They also include two sibling Odorrana species, namely the Okinawa Ishikawa’s frog Odorrana ishikawae and the recently described Amami Ishikawa’s frog Odorrana splendida, which are still listed as one species (Ishikawa’s frog Odorrana ishikawae (EN)) on the IUCN list. Most of the threatened species seen in the four islands are endemic to the area at the generic, specific, or subspecific level. Furthermore, a characteristic mixture of East Asian, South East Asian, and Oceanian floral elements can be seen on the islands, reflecting the climatic conditions and various historical processes of dispersals. The proposed property accounts for less than 1% of the whole land area of Japan, yet it accommodates about 17% of the nation’s endangered vascular plants. This area is therefore of the utmost importance for the conservation of Japan’s endangered plants.