Chiba Prefectural Government, Japan
Chiba Prefectural Government, Japan

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Suzuki M.,University of Tokyo | Miyashita T.,University of Tokyo | Kabaya H.,NPO Boso Wildlife Research Party | Ochiai K.,Natural History Museum and Institute | And 2 more authors.
Oikos | Year: 2013

Ungulate herbivory can fundamentally affect terrestrial vegetation at the landscape and regional levels, but its impact has never been analyzed from meta-community perspectives. Here, we study a meta-community of forest ground-layer plants in a warm-temperate region along a clear gradient of deer density interplaying with gradients of other environmental factors (forest type, sky openness and topographic wetness). Canonical corresponding analysis showed that deer density was the most important determinant of species distributions. These distributions conformed to a two-directional filtering model, which selects for competitive species at low deer density but favours herbivory-tolerant plants at high deer density, with these two directions counterbalancing each other when herbivory is intermediary. This resulted in a bi-directionally nested meta-community, in which local species richness was highest at intermediate levels of deer density, conforming also to the intermediate disturbance hypothesis. Our results suggest that herbivory can be the most important driver of meta-community structure in mesic systems; this contrasts with the results of earlier studies conducted in harsh environments, where species sorting by abiotic factors at early life stages reduced the role of biotic interactions, including herbivory. © 2012 The Authors. Oikos © 2012 Nordic Society Oikos.


Watanabe K.,Kyoto University | Mori S.,Gifu Keizai University | Tanaka T.,The Museum of Nature and Human Activities | Kanagawa N.,4 3 26 Honmachi | And 12 more authors.
Ichthyological Research | Year: 2014

The genetic population structure of the small cyprinid Hemigrammocypris rasborella, distributed widely in lowlands of western Japan, was examined using partial sequence data of mitochondrial DNA (mtDNA). Molecular phylogenetic analysis revealed that the populations of the western Kyushu region were markedly differentiated from all eastern populations, such that the groups would be comparable to different species; their divergence was inferred to have occurred in the Late Miocene–Pliocene. Also, a largely divergent mtDNA group (with divergence in the early Pleistocene) was found in the Sanyo and northeastern Shikoku regions, forming a secondary contact zone in the western Kinki with the eastern mtDNA group. To date, these aspects of the population structure of H. rasborella appear to be unique among lowland fishes in western Japan. Deeper understanding of the formation processes of freshwater faunas in western Japan will require further comparisons of the phylogeographic patterns and ecological traits of constituent species. © 2014, The Ichthyological Society of Japan.


Reimer J.D.,University of Ryukyus | Reimer J.D.,Japan Agency for Marine - Earth Science and Technology | Shah M.M.R.,University of Ryukyus | Sinniger F.,Florida State University | And 4 more authors.
Marine Biodiversity | Year: 2010

The dinoflagellate genus Symbiodinium is generally found in many tropical and subtropical marine invertebrates. Recently, reports have focused on free-living types. We examined free-living Symbiodinium from the Ogasawara (Bonin) Islands, a group of oceanic islands south of Japan. Examining sand samples, seven of eight initial isolates were successfully cultured. Genetic analyses of 18S, 28S and internal transcribed spacer (ITS) ribosomal DNA regions reveal that one isolate cultured with only IMK was identical to clade A isolated from coral reef sand in Okinawa, and four additional isolates cultured with only IMK comprised a new clade A lineage. Additionally, two isolates cultured with IMK and soil extract were closely related to a little-known divergent lineage within clade D. Our results demonstrate some free-living Symbiodinium types may have very wide distributions, and that utilizing different culturing techniques will further discovery of unique Symbiodinium lineages from environmental samples. © 2010 Senckenberg, Gesellschaft für Naturforschung and Springer.


Nakata K.,Public Works Research Institute | Hayashi N.,Natural History Museum and Institute | Ozaki M.,Chiba Biodiversity Center | Ohtaka A.,Hirosaki University | Miwa J.,Public Works Research Institute
Plankton and Benthos Research | Year: 2010

The North American invasive signal crayfish Pacifastacus leniusculus was designated as an 'Invasive Alien Species' by the Ministry of the Environment of Japan and by the Ministry of Agriculture, Forestry and Fisheries of Japan on 1 February 2006. We report the first record of P. leniusculus from the Kanto region (Chiba Prefecture), central Japan. Adult specimens of P. leniusculus were collected from the Tone River basin between September 2009 and January 2010. Ectosymbiotic crayfish worms (Annelida, Clitellata, Branchiobdellidae) were found on the crayfish and all specimens were identified as Sathodrilus attenuatus, which outside of its home range in North America occurs only in the Hokkaido and Fukushima Prefecture populations of P. leniusculus; thus suggesting that P. leniusculus in the Tone River basin was introduced from Hokkaido or Fukushima Prefecture. Signal crayfish is considered a cool water species and has been reported mostly in Hokkaido, northern Japan, but our findings strongly indicate that P. leniusculus has become established in a warm water area in central Japan, where the maximum water temperature is above 30°C in summer. These results indicate that P. leniusculus can inhabit warm water areas as well as cool areas and would be able to extend its distribution over a wide range in Japan. © The Japanese Association of Benthology.


Reimer J.D.,University of Ryukyus | Reimer J.D.,Japan Agency for Marine - Earth Science and Technology | Hirose M.,University of Ryukyus | Yanagi K.,Chiba Biodiversity Center | And 2 more authors.
Systematics and Biodiversity | Year: 2011

The Ogasawara (Bonin) Islands are oceanic islands approximately 1000 km south of mainland Japan noted for their high levels of both terrestrial and marine endemicity. Despite their unique location, the marine fauna of many taxa remains relatively under-examined. In this study, we specifically investigated the diversity of shallow water zoanthids (Cnidaria: Anthozoa: Hexacorallia) and their symbiotic zooxanthellae (Symbiodinium spp.) of the Ogasawara Islands for the first time. Using in situ field examinations combined with DNA sequencing and phylogenetic analyses, our results show the presence of five zoanthid species in the Ogasawara Islands; Zoanthus sansibaricus, Z. kuroshio, Palythoa tuberculosa, P. mutuki, and one potentially undescribed species of Palythoa. While most collected specimens were in symbiosis with clade C Symbiodinium as seen in southern Japan and other Indo-Pacific locations, one specimen of Z. kuroshio was unexpectedly in symbiosis with clade A, and no Z. sansibaricus colonies contained specific C1z type zooxanthellae previously observed at other locations. Overall, the Ogasawara Islands showed a lower zooxanthellate zoanthid species diversity (n = 5) than the non-oceanic Okinawa Islands (n > 10), which are at roughly the same latitude. Instead, the islands' relatively depauperate zoanthid/symbiont fauna more closely resembles that of the northern Izu Islands. © 2011 The Natural History Museum.


Katano O.,Japan National Research Institute of Fisheries Science | Sakuma T.,Fisheries Management Office | Iwasaki J.,Ibaraki Prefectural Freshwater Fisheries Experimental Station | Kita A.,Ibaraki Prefectural Freshwater Fisheries Experimental Station | And 6 more authors.
Japanese Journal of Conservation Ecology | Year: 2010

The channel catfish, Ictalurus punctatus, is an invasive alien species introduced from North America. We investigated the present status of the fish in Japan and found that it is widely distributed in the Abukuma, Tone, and Yahagi River systems, as well as in Lake Shimokotori. In 2008 and 2009, several channel catfish were also caught in Lake Hinuma and the Miya and Seta Rivers. We concluded that the distribution of channel catfish has rapidly expanded within natural rivers during the past several years. To avoid severe damage imposed by channel catfish to the river ecosystems and inland fisheries of Japan, risk assessments and examinations of the ecological characteristics and methods of capture of this fish species are urgently required.


Yoshimura M.,University of Shiga Prefecture | Miyata A.,University of Shiga Prefecture | Miyata A.,Kyoto University | Suzuki N.,Mie University | And 2 more authors.
Limnology | Year: 2015

The effects of larval cestode (Neogryporhynchus cheilancristrotus) infection on the reproduction of golden venus chub Hemigrammocypris neglectus and their population growth were estimated by analysis of the relationships between the abundance of cestodes and the breeding behavior of male chubs, as well as the fecundity of female chubs. N. cheilancristrotus causes a prominent abdominal distention in H. neglectus because of a hypertrophied hepatopancreas. Cestode infection displayed no negative relationship to chasing behavior by males of females or to the number of prenatal eggs in females. Thus, we conclude that cestode infection has little effect on the population growth of the host fish through reproductive behavior/fecundity, despite the prominent pathological change in the hepatopancreas. © 2015, The Japanese Society of Limnology.

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