Yakushima Island Research Articles

Crossability of a high-mountain dwarf variety of Lysimachia japonica (Primulaceae) endemic to Yakushima Island with its normal-sized lowland counterpart

A high-mountain dwarf plant of Lysimachia japonica (Primulaceae) endemic to Yakushima is reported to be very unique in the dwarfing mechanism at cell level, and the plant is one of the candidates to be a key species to reveal the unsolved molecular mechanism of taxon-specific body size of plant. In the present study, we examined the crossability between the dwarf plant of L. japonica and its normal-sized lowland counterpart, and self- and cross-compatibilities within each linage. The results indicate that both dwarfed and normal-sized L. japonica are self- and cross-compatible within each ecotype and are bidirectionally cross-compatible with each other, suggesting that this plant possesses optimum life historical traits for further genetic analysis in order to clarify the mystery of molecular mechanism of taxon-specific body size.

First Record of the Mycoheterotrophic Orchid Gastrodia uraiensis (Orchidaceae) from Yakushima Island, Japan

Flowering individuals of an unknown species of Gastrodia were discovered on Yakushima Island, Japan. While those plants were somewhat similar to gastrodia fontinalis, they had shorter inflorescences,

Effects of density, season, and food intake on sika deer nutrition on Yakushima Island, Japan

AbstractSika deer (Cervus nippon) suffer severe winter food limitation in northern Japan; however, plant food resources are available during winter in southern Japan and, consequently, deer nutritional status may not decrease there. To test this hypothesis, we measured seasonal changes in Riney's kidney fat index (RKFI) and stomach intake in 74 culled deer individuals from five areas with different deer densities on Yakushima Island, Japan. The average RKFI differed significantly among populations and ranged from 22.91 ± 11.91 to 76.23 ± 15.99. There was no significant correlation between RKFI and deer density. The total fresh weight of rumen contents also differed significantly among populations, ranging from 0.51 to 3.51 kg. Food intake and RKFI exhibited an L‐shaped distribution in the vicinity of a town ranch. However, we found that food intake had a significantly positive effect in populations at the other four locations, suggesting that changes in nutritional status were related to the quantity of deer rumen contents. Neither deer density nor season were significantly correlated with RKFI values. The average RKFI values exceeded 20 in all five locations. These findings indicate that the deer were not in a poor nutritional condition even in high density areas of >70 head/km2, which supports the above hypothesis. Notably, food intake varied among individuals in the same area, but was independent of body weight and age, which suggests that food selectivity differs between deer individuals.

A complete history of the establishment of Japanese sika deer on the Delmarva Peninsula: 100 years post-introduction

While many non-native species immediately express their negative qualities which encourage their management (even attempted eradication), some have long lag periods before the population begins to grow out of control. Sika deer have been problematic in many places where they were introduced as novelties or games species through hybridization or aggressive interactions with native deer. In attempt to better manage these species we need to know their native ecosystem. We provide evidence through summarized literature of the manner in which sika deer arrived on Delmarva from Yakushima Island in Japan via a multi-generational stopover in the United Kingdom. We also add morphological and genetic support that confirm the origins and help describe the path of introduction of sika deer to Maryland. We also summarize the growth and change in population size(s) over the last 100 years. This historic understanding is an essential part of coping with the persistent growth of a large, aggressive herbivore that is currently being managed as a game species. We summarize the possible impacts of sika deer including the displacement of native white-tailed deer. The management of this species needs to be carefully observed as they continue to spread throughout the critical saltmarsh of the Delmarva Peninsula.

Syngnathus chihiroe, a new species of pipefish (Syngnathidae) from southern Japan.

A new species of pipefish, Syngnathus chihiroe sp. nov., (Syngnathidae), is described on the basis of a single specimen collected off Yakushima Island (East China Sea), southern Japan in a depth of 160-162 m. The new species is readily distinguished from all congeners by the combination of the following characters: dorsal-fin rays 38, pectoral-fin rays 17, trunk rings 18, tail rings 40, subdorsal rings 3.25 + 10.0 = 13.25, head length 8.7 in standard length, snout length 2.3 in head length and snout depth 3.7 in snout length. The new species is similar to Syngnathus schlegeli Kaup 1853, the only other northwestern Pacific Ocean congener, characterized by dorsal-fin rays 30-47, trunk rings 18-20 and tail rings 38-46. However, it differs from S. schlegeli in having a greater number of pectoral-fin rays (17 in the former vs. 11-15 in the latter), and a short deep snout (snout length 2.3 in head length and snout depth 3.7 in snout length vs. 1.6-2.0 and 5.6-11.3, respectively).

Zircon U–Pb dating using LA-ICP-MS: Quaternary tephras in Yakushima Island, Japan

Zircon U–Pb dating using LA-ICP-MS was applied to three Quaternary tephras in Yakushima Island, southern Japan: the Anbo Tephra, the Koseda pyroclastic flow deposit (Ksd), and the Kikai-Tozurahara (K-Tz) Tephra. The obtained U–Pb ages were 0.73±0.04Ma (error shown as 95% confidence level) for the Anbo, 0.63±0.04Ma for the Ksd, and 0.17±0.05Ma for the K-Tz. These ages are consistent with or slightly older than those reported previously, which demonstrates the applicability of the U–Pb method to date zircons as young as ~0.1Ma. The K-Tz contains ~0.7–0.6Ma zircons, assumed to be derived from the Anbo and Ksd tephras. Because the K-Tz was originated from the Kikai Caldera, ~30km north of Yakushima Island, both the Anbo and Ksd were likely also derived from the same caldera system. Therefore our data and interpretation will contribute to elucidate the magmatic history of the Kikai Caldera whose latest eruption devastated prehistoric human settlements of southern Kyushu, Japan, and provide an improved chronostratigraphic constraint for Japan.

Historical logging and current successional status of old-growth Cryptomeria japonica forest on Yakushima Island

ABSTRACTEstimation of the current successional status of long-lived coniferous forests is difficult especially after several hundred years of human disturbance. However, in Cryptomeria japonica forest on Yakushima Island, the stumps generated by logging activities from the seventeenth to nineteenth centuries remain almost intact without intense rotting. From an inventory of these stumps and long-term monitoring of current stands for more than 25 years, we estimated the forest condition before logging and evaluated the current status of secondary succession. The size structure of Cr. japonica stumps suggested the stumps were composed of two different generations: the stumps of trees present before initiation of logging; and those of trees that regenerated after initiation of logging. In the current forest, the stem number of canopy species is decreasing and that of understory broad-leaved species is increasing. Regenerating Cr. japonica individuals are rare. Before the logging, the forest contained a larger number of larger Cr. japonica trees than the current forest. The results of monitoring the current forest suggested that all coniferous species, including Cr. japonica, were still undergoing self-thinning. The current Cr. japonica forest is in an intermediate stage of secondary succession, but the processes of succession are markedly different between the study plots, depending on their location or previous logging intensity.

Interspecies sexual behaviour between a male Japanese macaque and female sika deer.

Interspecies sexual behaviour or 'reproductive interference' has been reported across a wide range of animal taxa. However, most of these occurrences were observed in phylogenetically close species and were mainly discussed in terms of their effect on fitness, hybridization and species survival. The few cases of heterospecific mating in distant species occurred between animals that were bred and maintained in captivity. Only one scientific study has reported this phenomenon, describing sexual harassment of king penguins by an Antarctic fur seal. This is the first article to report mating behaviour between a male Japanese macaque (Macaca fuscata yakui) and female sika deer (Cervus nippon yakushimae) on Yakushima Island, Japan. Although Japanese macaques are known to ride deer, this individual showed clearly sexual behaviour towards several female deer, some of which tried to escape whilst others accepted the mount. This male seems to belong to a group of peripheral males. Although this phenomenon may be explained as copulation learning, this is highly unlikely. The most realistic hypothesis would be that of mate deprivation, which states that males with limited access to females are more likely to display this behaviour. Whatever the cause for this event may be, the observation of highly unusual animal behaviour may be a key to understanding the evolution of heterospecific mating behaviour in the animal kingdom.

First record of the jawfish Opistognathus trimaculatus Hiramatsu and Endo 2013 (Actinopterygii: Perciformes: Opistognathidae) from the East China Sea, with comments on its diagnosis

The rare jawfish Opistognathus trimaculatus Hiramatsu and Endo 2013 is newly recorded from the East China Sea, based on a single specimen collected from the west of Yaku-shima Island, Kagoshima, Japan. It was previously known only from Tosa Bay (type locality) and the Kii Channel, both located off the Pacific coasts of southern Japan. The new specimen, therefore, represents the first record of O. trimaculatus from the East China Sea, extending its known range approximately 640 km southwest from Tosa Bay. The species’ diagnosis is amended, with comments on interspecific variation.

Lecanorchis tabugawaensis (Orchidaceae, Vanilloideae), a new mycoheterotrophic plant from Yakushima Island, Japan.

A new species, Lecanorchis tabugawaensis Suetsugu & Fukunaga, sp. nov. from Yakushima Island, Kagoshima Prefecture, Japan, is described and illustrated. Lecanorchis tabugawaensis is similar to Lecanorchis taiwaniana, but it is easily distinguished by the straight column, the glabrous status of the base of the column, the almost entire and narrow labellum morphology, the shorter part of the column fused with the labellum and the glabrous status of the apical part of the adaxial labellum surface. The new species appears to be restricted to two locations, each consisting of only dozens of mature individuals, and is assessed as Critically Endangered [CR D1] according to IUCN Red List Categories and Criteria.

Three new brackish-water thalassocypridine species (Crustacea: Ostracoda: Paracyprididae) from the Ryukyu Islands, southwestern Japan.

We describe three new species of brackish-water ostracods representing two genera in the ostracod tribe Thalassocypridini from mangrove forests in the Ryukyu Islands, subtropical southwestern Japan, and provide their barcoding sequences for the mitochondrial cytochrome c oxidase subunit I (COI) gene. Mangalocypria ryukyuensis sp. nov. was found on Okinawa Island. We also found a Mangalocypria population on Ishigaki Island that was morphologically identical to M. ryukyuensis on Okinawa, but an individual differed by 4.7% in COI sequence (K2P distance) from an individual from Okinawa. This is the first record for Japan of a species in Mangalocypria. Paracypria longiseta sp. nov., obtained from Okinawa Island, is similar to Pontoparta hartmanni. Paracypria plumosa sp. nov. from Ishigaki Island is similar to Pa. adnata described from Yakushima Island, Japan. The COI genetic distance between individuals of Pa. longiseta and Pa. plumosa was roughly as large as that between either of these species and individuals in the Mangalocypria populations. Our study underscores that genera in Thalassocypridini may not represent natural groups, and that this tribe needs taxonomic revision.

Soil‐nutrient availability and the nutrient‐use efficiencies of forests along an altitudinal gradient on Yakushima Island, Japan

AbstractThe vegetation on Yakushima Island, Japan, grows on soils derived from Akahoya volcanic ash, released from the Kikai Caldera about 7300 years ago. The eruption was devastating and it is believed that primary succession and soil formation reinitiated across all altitudes at this point. We hypothesize that the concentrations of soil total phosphorus (P) and labile P fractions increase with increasing altitude because the soil formation has progressed less in upslope areas as a result of the cooler temperature and because of the ample P source of the volcanic ash. Conversely, we hypothesize that the concentration of soil inorganic nitrogen (N) decreases with increasing altitude. Available soil P and N would result in increasing P limitation downslope and increasing N limitation upslope, respectively. We studied soil P fractions and soil inorganic N, and P‐ and N‐use efficiencies of the seven forests on Yakushima along an elevation gradient (170–1550 m a.s.l.). Contrary to our hypotheses, soil total P, labile soil P fractions, and inorganic N decreased with increasing altitude. The P‐ and N‐use efficiencies of the forests were negatively correlated with the concentration of soil total active P (total P minus occluded P) and inorganic N, respectively. We suggest that progressive soil acidity and slower decomposition under cooler and wetter environments upslope must have dissolved the P contained in volcanic ash and accelerated P leaching. Forest ecosystems on Yakushima that show a distinct altitudinal zonation are, therefore, characterized by increasing P and N shortage with increasing altitude.

Contribution of Sepioteuthis sp. 1 and Sepioteuthis sp. 2 to oval squid fishery stocks in western Japan

The relative contribution of Sepioteuthis sp. 1 and Sepioteuthis sp. 2 to oval squid fishery stocks in western Japan was examined using microsatellite DNA and partial sequences of mitochondrial cytochrome oxidase subunit I. A total of 1718 Sepioteuthis spp. individuals from 19 populations were identified to determine the proportion of each species in fishery stocks. Samples from Tanegashima and Yakushima Islands in southwestern Japan were also examined to determine depth distributions. DNA was used to refer 233 (17.3 %) individuals to Sepioteuthis sp. 1 and 1421 (82.7 %) individuals to Sepioteuthis sp. 2. Sepioteuthis sp. 1 was found on the Pacific side of mainland Japan, but was predominant in Tanegashima (77.1 %) and Yakushima Islands (100 %), suggesting its distribution was limited by the warmer waters of the Kuroshio Current. In contrast, Sepioteuthis sp. 2 was most commonly found around mainland Japan. Whereas Sepioteuthis sp.1 was caught in 10 to 53 m depth, Sepioteuthis sp. 2 was caught in 2 to 30 m depth. Differences in the spatial and bathymetric distributions of these two species might reflect differences in temperature preference, spawning depth, and migration patterns. Our results would be useful for managing the fishery stocks and spawning grounds of both species.

The legal concept of ‘heritage’ in the world heritage convention: The case of Yakushima, Island

Abstract Yakushima Island (Yakushima) has been developed for eco-tourism, and it has been registered on the list of UNESCO world heritage (WH) sites. The inhabitants of Yakushima have derived great prosperity from their WH registration and are considered successful in Japan. In spite of the island’s strong economic growth due to tourism, there have been many social problems. The inhabitants, including tourist agencies and tour guides, are the primary agents of these social problems. In this paper, we explain that the causes of these social problems are rooted in a misinterpretation of the WH convention, especially the concept of ‘heritage’. We must define the meaning of ‘heritage’ and the related words in the convention. In doing this, it is necessary to introduce strictly defined legal terms from the civil law. In our civil law, the concept of ‘heritage’ is described as one concept, that is, joint-property or inheritance. Inheritance is owned jointly, and it consists of heirs and inheritance obligees, that is, all the peoples of the world. The inhabitants in Yakushima should recognize that they gave everyone from around the world the right to enjoy the naturale environment of their island after it was registered on the WH list.

Fine-scale genetic population structure of loggerhead turtles in the Northwest Pacific

Effective conservation of globally distributed marine species relies on identification of demographically independent populations to ensure that management actions are directed at the appropriate scale. This identification is particularly challenging for species with complex life histories when local breeding populations have not been adequately sampled. We used mtDNA to analyze the population structure of loggerhead turtles from a total of 555 samples collected from 12 nesting sites in Japan in the Northwest Pacific, including previously unsampled rookeries in the Ryukyu Archipelago, for a comprehensive coverage of the nesting distribution. We identified a total of 9 haplotypes based on 820 bp of the mtDNA control region, including 5 variants of a single previously described 380 bp haplotype. We discovered that 1 haplotype (CcP1.1) previously rare in the North Pacific is common in the Ryukyu Archipelago. Based on analysis of haplotype frequencies, we found significant differentiation among regionally grouped nesting populations (analysis of molecular variance p < 0.0001, df = 8; pairwise FST ranging from 0.033 to 0.145). Our results provide evidence to support the recognition of 3 management units (MU) within the NW Pacific Regional Management Unit (RMU). These include (1) the Ryukyu MU that includes Okinawa, Okinoerabu and Amami, (2) Yakushima Island MU and (3) a Mainland MU that includes Bousou, Enshu-nada, Shikoku, Kii and Eastern Kyushu. These new data from Japan will provide important baseline data for global genetic stock assessments and contribute to our understanding of the population structure, ecology and life history of this migratory marine species in the northern Pacific.

Volcanic history of the Kikai Caldera inferred from zircon U-Th-Pb dating on Quaternary tephras in Yakushima Island

Volcanic history of the Kikai Caldera inferred from zircon U-Th-Pb dating on Quaternary tephras in Yakushima Island

A theoretical approach for zone-based management of the deer population on Yakushima Island

The biological balance of Yakushima Island is currently being compromised by overpopulation of sika deer (Cervus nippon yakushimae). We predicted that the island’s deer population would continue to grow unless control efforts are raised threefold from their 2012 levels. To identify the best management practice for future implementation, we evaluated and compared the performances of three different zone-based management strategies. Under the current management scenario, the median population size of the sika deer on the island would temporarily decrease, but it would subsequently rebound. Under a scenario that allows management zones to be prioritized according to the occurrence of threatened plant species and deer population size, model simulations suggested that the scenario focusing on the central zone would show the best performance based on the probability of achievement of the management goal (assuming that there is no dispersal between zones). This course of action would lead to a decrease in the median deer population size and would further ensure a high probability of achieving the 2022 target population size across most zones (up to 85 %), even if catch levels were not increased. In a future study, we would need to conduct a more detailed analysis of plants and deer density distributions.

First documentation of the barnacle Fistulobalanus albicostatus (Cirripedia: Balanomorpha) as an epibiont of loggerhead sea turtle Caretta caretta

Epibionts on a nesting female loggerhead sea turtle Caretta caretta (Linnaeus, 1758; 92.1 cm straight carapace length and 70.7 cm straight carapace length) were examined on the island of Yakushima, Kagoshima, Japan (30.4156°N, 130.4394°S) on 16 June 2009 (Fig. 1a). Specimens were photographed, counted and identified at the lowest taxonomic level, and four species of barnacles were found: Chelonibia testudinaria (Linnaeus, 1758), Platylepas hexastylos (Fabricius, 1798), Stephanolepas muricata Fischer, 1886, and Fistulobalanus albicostatus (Pilsbry, 1916). The turtle barnacles C. testudinaria (n = 6), P. hexastylos (n = 42) and S. muricata (n = 1) are common on Japanese turtles (Hayashi 2012), while this is the first record of F. albicostatus (n = 4) on sea turtles. The acorn barnacle F. albicostatus is a common species in estuaries and mangroves and as a biofouling species on ships, and occurs in the waters of Japan, China, Taiwan and Korea (Newman and Ross 1976; Chan 2007). The barnacle has also been recorded in California waters as an invasive species (Bonnot 1935; Henry and McLaughlin 1975). Japanese loggerhead turtles migrate over the Pacific Ocean as developmental migration in their ontogenetic stages (Bowen et al. 1995); sea turtle migration allows F. albicostatus and possibly other organisms biofouling sea turtles to invade new habitats, as seen in a case of rapa whelk Rapana venosa (Valenciennes, 1846) recorded in Harding et al. (2011). In one example for F. albicostatus, a new geographic expansion into Norway by biofouling plastic tags on migrating birds was reported (Tottrup et al. 2010). Further studies are needed to examine the potential role of migratory animals such as sea turtles and birds as dispersal vectors of these hitchhikers.

Draft Genome Sequences of Sarcina ventriculi Strains Isolated from Wild Japanese Macaques in Yakushima Island.

We report the draft genome sequences of Sarcina ventriculi strains 14 and 17, both isolated from feces of wild Yakushima macaques (Macaca fuscata yakui). These genomic sequences will be helpful for the phylogenetic consideration of the family Clostridiaceae and understanding of the contribution of intestinal microbiota to the survival of Yakushima macaques.

Female philopatry and limited male-biased dispersal in the Ussuri tube-nosed bat, Murina ussuriensis

AbstractMale-biased dispersal and female philopatry are common traits among social mammals, often leading to elevated relatedness within social groups. However, exceptions do occur, with documented cases of female-biased dispersal, dispersal by both sexes, and philopatry of both sexes. In this study, we examined levels of dispersal and relatedness based on analyses of the mitochondrial D-loop and 12 nuclear microsatellite markers in the woodland specialist Ussuri tube-nosed bat ( Murina ussuriensis ), a relatively widespread, yet locally rare species that is thought to be threatened by loss of its forest habitats across its range. A total of 85 individuals were captured in lowland temperate forest on the island of Yakushima and 28 individuals in montane forest in Hokkaido, Japan. In the former, haplotypes showed extreme spatial clustering among females consistent with strong philopatry, but spatial mixing among males suggesting dispersal over short distances. These findings were broadly supported by microsatellite analyses, which indicated considerable genealogical structure within sampling locations but a lack of spatial structure, again indicating that some gene flow does occur in one or both sexes. The Hokkaido data, although limited, did not show these patterns and instead suggest that differences in environmental and behavioral variables may influence movement ecology of individuals at these 2 sites and consequently fine-scale genetic structure within this species.