Institute of Boninology

Ogasawara, Japan

Institute of Boninology

Ogasawara, Japan
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Ando H.,Japan National Institute of Environmental Studies | Sasaki T.,Institute of Boninology | Horikoshi K.,Institute of Boninology | Suzuki H.,Institute of Boninology | And 3 more authors.
Pacific Science | Year: 2017

The Red-headed Wood Pigeon, Columba janthina nitens, is an endemic and endangered subspecies of the Ogasawara Islands. This pigeon moves irregularly among island habitats. However, its range and patterns of movement, particularly between the Bonin and the Volcano Islands, which are two remote island groups approximately 150 km apart, remain unclear. In this study, we conducted a survey on the uninhabited Kita-Iwojima Island of the Volcano Islands to collect direct evidence of pigeon movement between the two island groups and to reveal their food resource availability. Pigeon food composition was also analyzed. During the study period in Kita-Iwojima, we observed two individuals banded in Chichijima in the Bonin Islands. Food composition was estimated by fecal DNA analysis and compared with a fruit census of Kita-Iwojima, which differed from fruits observed in two monitored islands of the Bonin Islands, Chichijima and Hahajima. The pigeons might move among these islands to use available food resources, reflecting limitations of food resources in a single island habitat. Fruits detected in feces of the pigeons on Kita-Iwojima were not from plants observed on the island but rather derived from plants observed on Chichijima and Hahajima, likely indicating high movement capacity of pigeons among the islands. However, the foraging habitat of the Red-headed Wood Pigeon is limited to areas of low elevation in Kita-Iwojima despite apparent food sources at higher elevations. Therefore, factors beyond food abundance, such as geographical features, might affect habitat use of pigeons on the island. © 2017 by University of Hawai'i Press.

Yabe T.,Rat Control Consulting | Horikoshi K.,Institute of Boninology | Hashimoto T.,Japan Wildlife Research Center
Pacific Science | Year: 2017

We investigated the cause of extraordinarily small body mass in Norway rats (Rattus norvegicus) living in the Ogasawara (Bonin) Islands in the subtropical climate zone in Japan. We compared body masses of Norway rats living in four localities, the Hahajima group of the Ogasawara Islands, uninhabited islands in Hokkaido in the subarctic climate zone, a business district in Yokohama, and an artificial islet in Tokyo Bay in the temperate climate zone. Regressions of body mass and age (in months; estimated from lens weight) showed that weights of Norway rats on the Hahajima Islands were about half the weights of rats in the other three localities. Crown length of the maxillary molar row was similar in three localities ( Hahajima, Hokkaido, and Yokohama), and both the head - body length and the tail length were similar in Hahajima and Hokkaido, suggesting that the low body mass of the Hahajima rats was due to environmental factors rather than genetic factors. Stomach contents of Norway rats on the Hahajima Islands were predominantly (95.2% by vol.) plant matter, which is not the usual food preference for the species. We hypothesize that a low-protein diet restricts body mass of Norway rats on the Ogasawara Islands. © 2017 by University of Hawai'i Press.All rights reserved.

Yamazaki D.,Tohoku University | Miura O.,Kochi University | Ikeda M.,Tohoku University | Kijima A.,Tohoku University | And 3 more authors.
Marine Biology | Year: 2017

Marine organisms with a planktonic larval stage can passively disperse long distance and are thus expected to have a wider distribution range and lower geographic variation. However, recent molecular phylogenetic studies have revealed that they often display a clear geographic genetic structure or even form a geographically fragmented species complex. These genetic divergences can be facilitated by the presence of dispersal barriers such as oceanic currents and/or by the limitation of suitable habitats. Using comprehensive phylogenetic analyses, we evaluate how such dispersal barriers shape genetic divergence and speciation in the intertidal snail genus Monodonta. Our phylogenetic analysis revealed various patterns of cladogenesis in Monodonta in East Asia. Genetic segregation between the Japanese and Ryukyu Archipelagos are detected in M. labio and M. perplexa perplexa. However, the relationship of geographical border and lineages does not correspond to those two because they show different habitat preference. M. labio distributed in the Japanese mainland is separated by the boundary corresponding to the point from which oceanic currents split into different directions. In contrast, species inhabiting various environments such as M. confusa are not genetically separated in Japan. In the peripheral oceanic Ogasawara Islands, two Monodonta species form each endemic lineage, although these two underwent different colonization processes to the islands. These findings suggest that the genus Monodonta has been genetically diversified around Japan, probably due to its correlations with dispersal ability, oceanic current, and habitat preferences. These factors may be effective causes for diversification of marine gastropods with a planktonic stage. © 2017, Springer-Verlag GmbH Germany.

Ando H.,Kyoto University | Kaneko S.,Kyoto University | Suzuki H.,Institute of Boninology | Horikoshi K.,Institute of Boninology | And 3 more authors.
Zoological Science | Year: 2011

The Japanese wood pigeon Columba janthina is endemic to islands of East Asia and is listed as Near Threatened by the International Union for Conservation of Nature (IUCN). One subspecies, C. janthina nitens, in particular, is at the greatest risk of extinction due to its small population size. To reduce the extinction risk of C. janthina, it is important to understand the species' present genetic status and to develop an appropriate conservation plan based on genetic data. We developed seven new microsatellite markers for two subspecies of C. janthina: C. janthina janthina and C. janthina nitens. We also confirmed the cross-use of one microsatellite marker developed for Columba livia var. domestica. Seven loci were polymorphic in C. janthina janthina, while two loci were polymorphic in C. janthina nitens. Using the markers, we performed preliminary analysis of genetic diversity and genetic structure within each subspecies. The expected heterozygosity ranged from 0.00 to 0.64 in C. janthina janthina and from 0.00 to 0.08 in C. janthina nitens. Each subspecies and each population within C. janthina janthina had different allele frequencies. C. janthina nitens exhibited far lower genetic diversity than C. janthina janthina. Furthermore, C. janthina nitens appears to have experienced strong genetic drift from a common ancestral population, inferred by STRUCTURE analysis. The markers described here may be useful for investigating genetic diversity and genetic structure of C. janthina populations, and could be used to estimate appropriate evolutionary significant unit and to guide development of a captive breeding program based on genetic information. © 2011 Zoological Society of Japan.

Sasaki T.,Institute of Boninology | Satake K.,Japan National Institute of Environmental Studies | Tsuchiya K.,Tokyo University of Marine Science and Technology
Japanese Journal of Limnology | Year: 2010

Stenomelania boninensis is a thiarid snail endemic to the Ogasawara (Bonin) Islands. Although an alien thiarid snail, Melanoides tuberculata, which presumably has a potential to replace native snails, was recorded from Chichijima in 2005, nothing is known concerning the relationships between these two species. Field surveys on the geographical distribution of the both species were conducted in 39 stream systems on eight islands of the Ogasawara Islands, including Mukojima, Chichijima and Hahajima. As a result, whereas S. boninensis was collected from 33 streams of five islands, M. tuberculata was collected from only five streams in Chichijima. In addition, whereas while S. boninensis was found at both natural and concrete bank sites in freshwater zones, M. tuberculata was found observed at concrete bank sites in both freshwater and tidal zones. The effects of a stream bank construction on both M. tuberculata and S. boninensis were also assessed. Quantitative samplings of the snails were conducted at six stations along the Yatsuse River in Chichijima during a period from immediately before to nine months after the construction was completed. Before the construction, S. boninensis and M. tuberculata coexisted in the reaches of the construction site. During the construction period, both snail species were eliminated by the diversion of all water from the stream. Whereas M. tuberculata recovered at the construction site three months after the construction, S. boninensis failed to recover even after nine months. Moreover, M. tuberculata expanded its distribution range to the upper reaches after the construction. In conclusion, a disturbance like a stream bank construction possibly induces the replacement of native species by aliens.

Abe T.,Japan Forestry and Forest Products Research Institute | Wada K.,Institute of Boninology | Kato Y.,Tokyo Metroplitan University | Makino S.,Japan Forestry and Forest Products Research Institute | Okochi I.,Japan Forestry and Forest Products Research Institute
Biological Invasions | Year: 2011

The alien predatory lizard, Anolis carolinensis, has reduced the insect fauna on the two main islands of the Ogasawara archipelago in Japan. As a result of this disturbance, introduced honeybees are now the dominant visitors to flowers instead of endemic bees on these islands. On the other hand, satellite islands not invaded by alien anoles have retained the native flower visitors. The effects of pollinator change on plant reproduction were surveyed on these contrasting island groups. The total visitation rates and the number of interacting visitor groups on main islands were 63% and 30% lower than that on satellite islands, respectively. On the main islands, the honeybees preferred to visit alien flowers, whereas the dominant endemic bees on satellite islands tended to visit native flowers more frequently than alien flowers. These results suggest that alien anoles destroy the endemic pollination system and caused shift to alien mutualism. On the main islands, the natural fruit set of alien plants was significantly higher than that of native plants. In addition, the natural fruit set was positively correlated with the visitation rate of honeybees. Pollen limitation was observed in 53.3% of endemic species but only 16.7% of alienspecies. These data suggest that reproduction of alien plants was facilitated by the floral preference of introduced honeybees. © 2010 Springer Science+Business Media B.V.

Ando H.,Kyoto University | Kaneko S.,Kyoto University | Suzuki H.,Institute of Boninology | Horikoshi K.,Institute of Boninology | And 2 more authors.
Journal of Zoology | Year: 2011

The endangered black-footed albatross Phoebastria nigripes exhibits strong nest fidelity and natal philopatry. These biological features can strongly affect population dynamics and population genetic structure. Therefore, for its long-term conservation, it is important to estimate genetic diversity and population genetic structure. We performed genetic analyses, using 11 polymorphic microsatellite markers of 77 black-footed albatrosses from six breeding colonies on the Bonin Islands, an important breeding area in the western North Pacific. In the population-based analysis, AMOVA results showed that almost all genetic variations existed among individuals in each subpopulation. Most FST and RST values among the subpopulations were 0.000 and the migration rates were 3.0-5.3%. In the individual-based analysis, the results of structure analysis suggested that all the individuals were clustered into the same genetic group. In the principal coordinates analysis based on kinship among individuals, most of the individuals were distributed as a single group. Although albatross species are strongly philopatric, the present results indicate a lack of population genetic differentiation among six subpopulations and the presence of sufficient gene flow to maintain the genetic homogeneity. In the principal coordinates analysis, a few individuals were genetically different from most of the other individuals, indicating a probability of immigration. The black-footed albatrosses on the Bonin Islands are in a good condition to maintain genetic diversity and can be treated as a single genetic management unit. © 2010 The Authors. Journal of Zoology © 2010 The Zoological Society of London.

Kawakami K.,Japan Forestry and Forest Products Research Institute | Eda M.,Tottori University | Eda M.,Hokkaido University | Horikoshi K.,Institute of Boninology | And 3 more authors.
Condor | Year: 2012

Bryan's Shearwater (Puffinus bryani) was described in 2011 on the basis of a specimen collected on the Midway Atoll in 1963. This specimen and another recorded on Midway in the early 1990s are the sole reliable rec ords to date. Since 1997, we have found six specimens of a remarkably small Puffinus shearwater morphologically similar to Bryan's Shearwater on the Bonin Islands, northwestern Pacific. In this study, we examined the Bonin samples genetically and confirm that they are of Bryan's Shearwater. A morphological analysis suggests that the small body size and relatively long tail are characteristics of this species. Because the most rec ent individual was found on an islet to the north of Chichijima Island in 2011, the species has evidently survived in the Bonin Islands, where it may breed, although the exact location remains unclear. Three of the individuals found on an islet off Chichijima Island were carcasses preyed upon by black rats (Rattus rattus). Attempts were made to eradicate rats from this island in 2008, and rats may pose a problem on other islands where the shearwaters may breed. Regardless, Bryan's Shearwater appears to be very rare and threatened on the Bonin Islands. To conserve this species effectively, its breeding sites must be identified and the infesting rats eradicated. © The Cooper Ornithological Society 2012.

Okada A.,Kitasato University | Suzuki H.,Institute of Boninology | Inaba M.,Institute of Boninology | Horikoshi K.,Institute of Boninology | Shindo J.,Kitasato University
Acta Chiropterologica | Year: 2014

The Bonin flying fox (Pteropus pselaphon) is endemic to the Ogasawara Islands, a collection of small oceanic islands in the Pacific Ocean. It inhabits only five islands: Chichi-jima, Haha-jima, Kita-iwo, Iwo, and Minami-iwo (arranged from north to south). Hahajima and Kita-iwo, the most widely spaced islands, are separated by a distance of about 160 km. The islands have different histories in the modern era with respect to human activity. At present, P. pselaphon population sizes exceed 100 on Chichi-jima and Minamiiwo, but the species is rare on the other three islands. Loss of genetic diversity is of concern because of the small population sizes. We obtained samples from three of the five islands - Chichi-jima, Kita-iwo, and Minami-iwo - and investigated species genetic diversity and genetic structure based on mitochondrial DNA (mtDNA) control region sequences and microsatellite markers. Different mtDNA haplotypes were found in each island population. Based on the mtDNA sequence data, P. pselaphon displayed a cryptic genealogy, as haplotypes on each island did not cluster together. The microsatellite marker data, however, revealed a clear genetic structure among the island populations, suggesting the absence of recent inter-island gene flow. Based on these results, we propose that the individual island populations are not evolutionarily significant units, but should be conserved collectively as a single management unit. © Museum and Institute of Zoology PAS.

Ando H.,Japan National Institute of Environmental Studies | Setsuko S.,Japan Forestry and Forest Products Research Institute | Horikoshi K.,Institute of Boninology | Suzuki H.,Institute of Boninology | And 5 more authors.
Ibis | Year: 2016

We studied the feeding ecology of the critically endangered Red-headed Wood Pigeon Columba janthina nitens, a subspecies endemic to a very remote and highly disturbed oceanic island chain, the Ogasawara Islands. An analysis based on high-throughput sequencing (HTS) was undertaken on 627 faecal samples collected over 2 years from two island habitats, and food availability and the nutrient composition of the major fruits were also estimated. The HTS diet analysis detected 122 food plant taxa and showed clear seasonal and inter-island variation in the diet of the Pigeons. The results indicated a preference for lipid-rich fruits, but the diet changed according to the availability of food resources, perhaps reflecting the foraging strategy of the Pigeons in isolated island habitats with poor food resources. Pigeons also frequently consumed introduced plants at certain times of year, perhaps compensating for the lack of preferred native food resources. However, the degree of dependence on introduced plants appeared to differ between the two island habitats, so the different impacts of introduced plant eradication on the foraging conditions for the Pigeons on each island should be considered. HTS diet analysis combined with field data may be useful for monitoring the foraging conditions of endangered species and may also inform an appropriate conservation strategy in oceanic island ecosystems with complicated food webs that include both native and introduced species. © 2016 British Ornithologists' Union.

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