Yakushima Island Research Articles

Warmer air temperatures do not negatively affect body size and emergence success of loggerhead turtle (Caretta caretta) hatchlings at Yakushima Island, Japan, the largest rookery in the North Pacific

Warmer air temperatures do not negatively affect body size and emergence success of loggerhead turtle (Caretta caretta) hatchlings at Yakushima Island, Japan, the largest rookery in the North Pacific

Geographical and seasonal variation of plant taxa detected in faces of Cervus nippon yakushimae based on plant DNA analysis in Yakushima Island

AbstractRecently, plant DNA analysis of feces has been successfully used to evaluate the food species composition of sika deer Cervus nippon. Here, we applied this method to Yaku‐sika C. nippon yakushimae, which increased its population and had a great negative impact on understory vegetation in Yakushima Island. We identified food plants of C. nippon yakushimae by sequencing chloroplast DNA fragments (rbcL region) of plants remaining in feces collected in the field in April, June, August, and October 2018, using a next‐generation sequencer. We collected feces from populations in two areas where populations have been managed by capture and three areas where those were not managed. The top two food plants in terms of the number of sequences determined were evergreen tall trees in all five areas. In addition to evergreen trees, understory herbaceous plants, including ferns, were included in the top 15 taxa in all areas. The diversity of food plants was higher in the managed areas than in the unmanaged areas. These results indicate that evergreen tall trees are the primary food plants of C. nippon yakushimae, but deer also forage on herbaceous plants as a side dish. Under this side dish effect, understory vegetation is reduced even under the high availability of food resources from tall trees. The high diversity of food plants in the managed areas suggested that understory plant diversity was restored when deer density was reduced by management.

Latitudinal cline in the foraging dichotomy of loggerhead sea turtles reveals the importance of East China Sea for priority conservation

AbstractAimQuantifying the importance of habitat areas for conservation of highly migratory marine species with complex life histories can be challenging. For example loggerhead turtles (Caretta caretta) nesting in Japan forage both oceanically and neritically after their reproductive period. Here, we aimed to quantify the proportions of turtles using these two contrasting habitats (foraging dichotomy) to suggest priority conservation areas.LocationNorth Pacific Ocean.MethodsWe examined the occurrence of foraging dichotomy at three nesting sites (Ishigaki, Okinoerabu Islands and Ichinomiya) based on stable isotope analysis of the egg yolks for 82 turtles and satellite tracking of post‐nesting migration for 12 turtles. Moreover, we used the data of three other sites from previous studies (Yakushima Island, Minabe and Omaezaki).ResultsTwo neritic foraging grounds (East China Sea and the coastal area of the Japanese archipelago), and an oceanic ground (North Pacific Ocean) were identified. We found a latitudinal cline with respect to the occurrence of foraging dichotomy; >84% of the females nesting at southern sites (Ishigaki and Okinoerabu Islands), 73% at middle sites (Yakushima Island and Minabe) and <46% at northern sites (Omaezaki and Ichinomiya) were neritic foragers; the proportion of oceanic foragers increased at northern sites. Based on the annual number of nests in the entire nesting region of Japan, satellite tracking and the latitudinal cline of foraging dichotomy, we estimated that 70% and 9% of annual nesting females in Japan utilize the neritic foraging habitat in the East China Sea and the coastal area of the Japanese archipelago, respectively, and that and 22% utilize the oceanic habitat of the North Pacific Ocean.Main conclusionsThe East China Sea represents a critical foraging habitat for the North Pacific populations of endangered loggerhead sea turtles. Our findings emphasize the need for international management to ensure their protection.

Development of paternally‐inherited Y chromosome simple sequence repeats of sika deer and their application in genetic structure, artificial introduction, and interspecific hybridization analyses

AbstractThe effect of sex‐biased dispersal in mammalian ecology and evolution can be elucidated by focusing on maternally or paternally inherited DNA polymorphisms. In sika deer, the genetic structure of the maternal lineage has been clarified by studies based on mitochondrial DNA variation. However, the genetic structure of the paternal lineage has not been well analyzed due to the limited number of point mutations in Y chromosome sequences. In this study, we focused on mutations of highly polymorphic simple sequence repeats (SSRs) in the Y chromosome and developed 16 Y chromosome SSR markers to evaluate male‐biased dispersal in sika deer. In total, 55 alleles and 31 multi‐locus haplotypes were detected from these 16 loci, revealing clear genetic differentiation among populations (F′ST = 0.783). In particular, there were unique alleles for the native individuals on Tanegashima and Yakushima Islands and introduced exotic individuals from Taiwan. These markers are highly useful for evaluating not only historical male‐mediated dispersal, genetic structure, and demography of the native populations in Japan, but also the impact of artificial introductions on hybridization, especially the introgression of alleles from escaped farmed individuals to native populations.

Molecular phylogeny and taxonomy of the Hydrangeaserrata complex (Hydrangeaceae) in western Japan, including a new subspecies of H.acuminata from Yakushima.

According to the contemporary classification of Hydrangea native to Japan, H.serrata is a polymorphic species including six varieties. We discovered a plant identified as H.serrata, but morphologically distinct from previously known varieties, in Yakushima island where approximately 50 endemic species are known. To determine the relationship of this plant with previously known varieties, we examined morphology and constructed a highly resolved phylogeny of H.serrata and its relatives using three chloroplast genomic regions, rbcL, trnL intron, psbA-trnH, and two nuclear genomic regions, ITS1 and ITS2, and Multiplex ISSR genotyping by sequencing (MIG-seq). Based on these morphological and phylogenetic observations, we describe Hydrangeaacuminatasubsp.yakushimensissubsp. nov. as a newly discovered lineage in Yakushima, Japan and propose Hydrangeaminamitaniistat. nov. and Hydrangeaacuminatasubsp.australisstat. nov. which were previously treated as varieties of H.serrata.

First Japanese records of Antennarius biocellatus (Antennariidae) from Okinawa-jima and Yaku-shima islands

First Japanese records of <i>Antennarius biocellatus</i> (Antennariidae) from Okinawa-jima and Yaku-shima islands

High-Throughput Sequencing Covers Greater Nematode Diversity than Conventional Morphotyping on Natural Cedar Forests in Yakushima Island, Japan

High-Throughput Sequencing Covers Greater Nematode Diversity than Conventional Morphotyping on Natural Cedar Forests in Yakushima Island, Japan

First specimen-based record of terminal phase individual of Scarus xanthopleura (Perciformes: Scaridae) from Japan, with first record of the species from Yaku-shima island, southern Japan

First specimen-based record of terminal phase individual of <i>Scarus xanthopleura</i> (Perciformes: Scaridae) from Japan, with first record of the species from Yaku-shima island, southern Japan

The genus Rhyacophila Stephens (Trichoptera, Rhyacophilidae) in Yakushima Island, northern Ryukyu, southwestern Japan.

This study revises the caddisfly genus Rhyacophila Stephens, Rhyacophilidae, for Yakushima Island within the northern Ryukyu Archipelago in southwestern Japan. Four new species are described based on adults: Rhyacophila yakushima sp. nov. of the R. anatina Species Group, R. arakawa sp. nov. of the R. lieftincki Species Group, R. miyanoura sp. nov. of the R. yosiiana Species Group, and R. nagata sp. nov. of the R. ulmeri Species Group. Additionally, two species are recorded for the island for the first time: R. brevicephalaIwata 1927, a Japanese species, and R. shikotsuensis Iwata 1927, an East Asian species.

Tourism and Counterurbanization in a Low-Amenity Peripheral Island: A Longitudinal Study at Yakushima Island in Kagoshima, Japan

This research explored the long-term relation between tourism development and counterurbanization in a remote island in Japan, as the longevity of in-migrants’ role in low-amenity tourism destinations has been questioned. Using data collected over 10 years at Yakushima Island, the study investigated the island’s population trend, in-migrants’ motivation for relocation, their contributions to tourism, and the lives on the island. The results showed that the trend of population growth differed among Yakushima’s 24 villages likely because of accessibility, proximity to tourism attractions, the weather, and housing availability. Yakushima’s natural environment was the key factor in in-migrants’ migration choice. Encounters and connections with people on the island were found to be another important factor. In-migrants introduced ecotours as an innovation in the 1990s, and thereafter, many in-migrants moved to Yakushima with high aspirations of becoming tour guides. Tourism stagnated starting in 2008, and some in-migrants began moving out of the island. Despite the overall downward trend of tourism, an increase in international tourists created a niche market before the COVID-19 pandemic, attracting foreign in-migrants as tourism entrepreneurs in recent years. Similar to the main driver for Japanese in-migrants’ relocation, nature was also the main motivation for international tourists’ relocation.

Effects of tree-root exudates on the solubilization of phosphorus adsorbed to non-crystalline minerals in the rhizosphere volcanic soils on Yakushima Island, Japan

Effects of tree-root exudates on the solubilization of phosphorus adsorbed to non-crystalline minerals in the rhizosphere volcanic soils on Yakushima Island, Japan

Spatial Genetic Structure of the Sika Deer (Cervus nippon) Population on Yakushima: Significant Genetic Differentiation on a Small Island

The sika deer population on Yakushima Island exhibits high genetic diversity despite the small size of the island. We hypothesized that the high genetic diversity of the population had been maintained by the population structure, which included several subpopulations among which gene flow was limited. To test this hypothesis, we analyzed the spatial genetic structure of the population using 12 microsatellite loci. Two and four subpopulations were detected by STRUCTURE (stN and stS) and GENELAND (glN, glE, glS, and glW) software, respectively. The basic genetic structure assigned by STRUCTURE was supported by GENELAND, while stN and stS were further separated into two subpopulations (glN and glE; glS and glW, respectively) by GENELAND. All pairwise genetic differentiations between the two and four subpopulations were significant. These results demonstrated that the Yakushima population was structured into genetically distinct subpopulations. Although the location of the western boundary between stN and stS corresponded with a large river, no landscape or biological feature could be identified for the eastern boundary. We discussed the relationships between the genetic structure and management units designed by the local government and concluded that the Yakushima population should be managed based on their spatial population structures considering multiple time scales.

屋久島における絶滅危惧植物保護柵内外での植被率・種数・種組成の変化：防鹿柵による保護と光環境の影響の評価

屋久島における絶滅危惧植物保護柵内外での植被率・種数・種組成の変化：防鹿柵による保護と光環境の影響の評価

Genetic characteristics of the amphidromous fish Ayu Plecoglossus altivelis altivelis (Osmeriformes: Plecoglossidae) on Yaku-shima Island in Japan, the southernmost population of the subspecies.

The Ayu (Plecoglossus altivelis altivelis) population on Yaku-shima Island, Kagoshima Prefecture, Japan represents the southernmost population of the subspecies and is considered to be facing extinction. We investigated the genetic characteristics of Ayu in the Miyanoura River (MYU) in the northeast of the island and the Kurio River (KRO) in the southwest of the island, using partial sequences of mitochondrial (mt) control region and polymorphic microsatellite (simple sequence repeat: SSR) loci. The mtDNA analysis revealed that the Yaku-shima Island population was significantly differentiated from other Ayu populations; additionally, the MYU and KRO populations were significantly different from each other in terms of mtDNA (pairwise ΦST = 0.5826, P < 0.01) and SSR (pairwise ΦST = 0.1598, P < 0.01) analyses, indicating very little or no gene flow between them. The mtDNA haplotype diversity values were minimal for KRO and somewhat lower for MYU (h = 0.8176) than for each population from the mainland of Japan (Honshu-Kyushu) and the Korean Peninsula (h = 0.9905-1.0000). The mean values of expected heterozygosity (He) of SSRs were also lower in KRO (mean He = 0.555) than in MYU (mean He = 0.649). A considerably small effective population size (Ne = 100.1 for MYU, 151.2 for KRO) and a bottleneck effect for Yaku-shima Island population were suggested by SSR analysis. These findings underscore the importance of monitoring the genetic diversity of Ayu on Yaku-shima Island and the necessity of designing conservation policies for each river's population.

Stomach and colonic microbiome of wild Japanese macaques.

Within the gastrointestinal tract, the physiochemical microenvironments are highly diversified among the different stages of food digestion. Accordingly, gut microbiome composition and function vary at different gut sites. In this study, we examine and compare the compositional and functional potential between the stomach and colonic microbiome of wild Japanese macaques (Macaca fuscata yakui) living in the evergreen forest of Yakushima Island. We find a significantly lower microbial diversity in the stomach than in the colon, possibly due to the stomach's acidic and aerobic environment, which is suboptimal for microbial survival. According to past studies, the microbial taxa enriched in the stomach are aero- and acid-tolerant. By functional prediction through PICRUSt2, we reveal that the stomach microbiome is more enriched in pathways relating to the metabolism of simple sugars. On the contrary, the colonic microbiota is more enriched with fiber-degrading microbes, such as those from Lachnospiracea, Ruminococcaceae, and Prevotella. Our study shows a clear difference in the microbiome between the stomach and colon of Japanese macaques in both composition and function. This study provides a preliminary look at the alpha diversity and taxonomic composition within the stomach microbiome of Japanese macaques, a hindgut-fermenting nonhuman primate.

Photograph-based records (including first records from Japan and Ryukyu Islands) of eight fish species from Yaku-shima island, Osumi Islands, Japan

Photograph-based records (including first records from Japan and Ryukyu Islands) of eight fish species from Yaku-shima island, Osumi Islands, Japan

Fecal metabolite analysis of Japanese macaques in Yakushima by LC-MS/MS and LC-QTOF-MS.

We performed a comprehensive fecal metabolite analysis using LC-MS/MS and LC-QTOF-MS approaches as a preliminary study. Feces of Japanese macaques on Yakushima Island were collected from five monkeys at two separate locations. Using the former methodology, 59 substances such as free amino acids, nucleotides, nucleosides and nucleic acid bases, and organic acids in the citrate cycle were quantitatively detected and successfully differentiated in two different monkey groups by the concentrations of nucleic acid metabolites and free amino acids. In the latter, around 12,000 substances were detected both by positive and negative mode in each sample. Differences in signal intensities were observed between two monkey groups in the concentrations of plant secondary metabolites such as cyanogenic glycosides, flavonoids, and phenolics.

Integrative taxonomy reveals multiple lineages of the spider genus Cybaeus endemic to the Ryukyu Islands, Japan (Arachnida : Araneae : Cybaeidae)

The epigean spiders of the genus Cybaeus L. Koch, 1868 are known to have diversified in western North America and the Japanese Archipelago. To date, ~80 species of Cybaeus are known from Japan, but they have not previously been recorded from the Ryukyu Islands that harbour a diversity of endemic species. Here we describe eight new species of Cybaeus from the Ryukyu Islands, extending the range of Cybaeus southward to the central Ryukyus. Both sexes of each of the new species are described, and their phylogenetic relationships are estimated using nuclear and mitochondrial gene markers. Although Cybaeus okumurai, sp. nov. and C. kumadori, sp. nov. possess genital features that are common in the other Japanese congeners, the other six species (C. yakushimensis, sp. nov., C. kodama, sp. nov., C. amamiensis, sp. nov., C. aikana, sp. nov., C. tokunoshimensis, sp. nov., and C. hikidai, sp. nov.) are characterised by an elongated embolus and tubular spermathecae. These unique genital characteristics and the phylogeny recovered here suggest that these features evolved independently among the Japanese and Ryukyu Cybaeus species. Phylogenetic analyses highlight an unusual biogeographical pattern in which C. yakushimensis and C. kodama endemic to Yakushima Island in the northern Ryukyus are related to species distributed in the central Ryukyus. In contrast, our phylogeny suggests that C. okumurai from Tanegashima Island in the northern Ryukyus is sister to C. ashikitaensis (Komatsu, 1968), distributed in Kyushu of the Japanese Archipelago. The retreat constructs and sympatric distribution of Cybaeus found among the Ryukyus are also briefly discussed. ZooBank: urn:lsid:zoobank.org:pub:640D15AA-17F4-48EE-88B4-485CFF8FCD60

National geographic distribution and number of TV nature programs across the Japanese archipelago

Cultural ecosystem services (CES) represent the intangible dimensions of the links between people and ecosystems. The evaluation and mapping of CES are critical and can be deeply involved in policy and decision-making concerning the management of ecosystems. Many previous studies have evaluated CES occurred through on-site and proximate contacts with nature such as walking in the forest, watching wildlife, or enjoying landscapes. However, fewer studies evaluated CES occurred in an off-site and distant way through conventional media such as TV and radio, and their spatially explicit evaluations are particularly rare. This paper focused on nature TV programs in Japan as an indicator of CES related to education, aesthetic enjoyment, and nature experience. We revealed the geographical distribution of nature programs across the Japanese archipelago. The associations of the number of TV programs with a range of key factors are discussed. The number of nature programs, and the temporal trends in such associations are explained. We obtained 4,117 nature programs that covered 1,691 locations across the Japanese archipelago between 2004 and 2017. We found that many nature programs dealt with World Natural Heritage Sites (WNHS) and World Cultural Heritage Sites (WCHS), including the Shiretoko peninsula (85 programs), Yakushima island (35 programs), Mt. Fuji (52 programs), and the mountainous areas around the Japanese Alps. In general, the number of Hyakumeizan (100 famous Japanese mountains) and the proportion of WNHS, WCHS, and lake areas within the search radii of 5, 10, and 15 km from the geotagged location of nature program were significantly positively correlated with the number of nature programs across the study period (2004–2017). In particular, the presence of famous mountains has become a relevant predictor of the number of nature programs since around 2012, consistent with the rise of mountaineering and hiking trends in Japan. Our result suggests that the designation as WNHS and WCHS would facilitate maintaining and managing invaluable nature and cultural landscapes of outstanding universal value, and thereby contributing to provide CES through TV programs.

Of the sea and volcano: A petrographic provenance investigation of locally produced and imported ware of Pre-Younger Dryas Tanegashima Island, Japan

In the southern part of Kyushu Island in southern Japan and the small islands further south the earliest pottery is found beneath the Satsuma tephra, which has been well dated to ca. 12,800 cal BP. Here we focus on Incipient Jomon pottery, 14,000/13,500–12,800 cal BP, from the Sankakuyama I site on Tanegashima Island. Previous visual analysis of the fabrics suggested that about half of the vessels were not locally made. In this study, we conducted both ceramic and raw material petrography and an electron microprobe study on samples of pottery. Our results indicate that pottery was mainly produced in situ, away from the coast, but that there is some clear non-local material which came from either Yakushima Island or Kyushu Island proper. Yakushima has no reported Incipient Jomon sites. There should be undiscovered sites on Yakushima if pottery circulated from there rather than Sankakuyama I residents embedding production in their logistical moves on Yakushima. Minor signatures of non-local geology in locally produced pottery are probably the result of volcanic eruptions and sea currents. Pottery production began when Tanegashima was disconnected from Kyushu and probably about to be separated from Yakushima. During the Incipient Jomon period, Tanegashima had become isolated. We conclude that pottery producers were hunter-gatherers who were mainly sedentary, living in a mild environmental with ecotone properties. They occasionally engaged in costly communication and exchange, which may have involved transporting pottery by watercraft and on foot, to buffer risks. Our study is among the first to investigate the pottery economy of the late Pleistocene and the decisions made by its producers and users in response to environmental variability and change. The research contributes to the debate on the origins of pottery and the Upper Paleolithic to Neolithic transition.