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Koyanagi T.F.,Tokyo Gakugei University | Akasaka M.,Tokyo University of Agriculture and Technology | Oguma H.,Japan National Institute of Environmental Studies | Ise H.,Regional Environmental Planning Inc.
Plant Ecology | Year: 2017

Habitat losses occur non-randomly within human-modified landscapes, resulting in high spatial heterogeneity of local habitat histories. Although local habitat history can modulate the existence of extinction debt (i.e., the number of populations predicted to become extinct) in a landscape, its role in detecting extinction debt has not been examined explicitly. We aimed to compare the detectability of extinction debt among populations of an endangered semi-natural grassland species, Echinops setifer (Compositae), in the grassland landscape of Mt. Aso, Japan. We classified populations into three groups that differed in local habitat history: stable (habitat loss ≤30% since the 1930s), moderately decreased (30% < loss ≤ 90%), and severely decreased (loss >90%). We then evaluated whether the effects of habitat areas during the 1930s and 2000s varied among groups to explain population size by GLMMs and estimated coefficient of explanatory variable by Bayesian MCMC methods. Within the groups, stable group showed significant positive relationships with both past and current habitat areas. The moderately decreased group only showed significant positive relationships with past habitat areas, indicating the existence of extinction debt in these populations. The severely decreased group only showed significant positive relationships with current habitat areas, indicating that they may have already paid their extinction debt because the rate of grassland loss exceeded the extinction threshold. Even within the same landscape, extinction debt varied in response to local habitat history. In spatially heterogeneous landscapes, evaluation of effects of local habitat history can elucidate the habitat-based extinction risks for plant populations. © 2017 Springer Science+Business Media Dordrecht


Ozaki K.,Japan Forestry and Forest Products Research Institute | Sayama K.,Japan Forestry and Forest Products Research Institute | Ueda A.,Japan Forestry and Forest Products Research Institute | Ito M.,Japan Forestry and Forest Products Research Institute | And 4 more authors.
Annals of the Entomological Society of America | Year: 2011

Evaluation of species diversity for highly diverse taxa is extremely time-consuming and costly; thus, there is a need to develop efficient sampling strategies. We established a short-term, efficient sampling scheme to produce samples that represent a full-season sampling of moth assemblages with a high degree of seasonality. We sampled adult moths monthly for the duration of the moth flying season by using light traps in five forest stands in a cool-temperate region in central Hokkaido, northern Japan. From this sample, we generated various subsamples that reduced the sampling period and the number of traps per stand, and tested whether these subsamples provide estimates of species richness, abundance, and species turnover representative of those revealed by the whole season sample. Comparisons between the whole season sample and each subsample indicated that setting one light trap on a night in July and August, which shortened the sampling period to 25% and reduced sample size to 38%, was the most efficient sampling scheme to estimate abundance, species richness, and similarity in the whole season sample. The comparisons also suggest that it is efficient to use rarified species richness as a species richness estimator, and the Bray-Curtis index or Morisita's CÎ" for estimating species turnover between sites in moth assemblages. © 2011 Entomological Society of America.


Sato T.,Kyoto University | Egusa T.,University of Tokyo | Fukushima K.,Kyoto University | Oda T.,University of Tokyo | And 6 more authors.
Ecology Letters | Year: 2012

Nematomorph parasites manipulate crickets to enter streams where the parasites reproduce. These manipulated crickets become a substantial food subsidy for stream fishes. We used a field experiment to investigate how this subsidy affects the stream community and ecosystem function. When crickets were available, predatory fish ate fewer benthic invertebrates. The resulting release of the benthic invertebrate community from fish predation indirectly decreased the biomass of benthic algae and slightly increased leaf break-down rate. This is the first experimental demonstration that host manipulation by a parasite can reorganise a community and alter ecosystem function. Nematomorphs are common, and many other parasites have dramatic effects on host phenotypes, suggesting that similar effects of parasites on ecosystems might be widespread. © 2012 Blackwell Publishing Ltd/CNRS.


Ito G.,Hokkaido University | Ito G.,Regional Environmental Planning Inc
Insecta Matsumurana | Year: 2015

Ito, G. 2015. A systematic study of the grashopper tribe Podismini in Japan (Orthoptera: Acrididae). Ins. matsum. n. s. 71: 1-119. This research presents evaluation of morphology in systematics of the tribe Podismini through the following studies. Morphology of the Podismini is studied and their transformation series are discussed by examination of the body parts including the male and female genitalia. Detailed descriptions of the female internal genitalia of the grasshoppers are given firstly. The terminology of the female internal genitalia is revised. Phylogenetic relationships among 13 podismini genera in the Far East are inferred on the basis of morphology using cladistic methodology. The topology of the consensus tree is somewhat similar to that of the mtDNA and/or rDNA tree proposed previously. Based on the result, subtribes are revised: a new subtribe Tonkinacridina is proposed for the genera Tonkinacris, Sinopodisma, Fruhstorferiola and Parapodisma, excluding them from the subtribe Miramellina. The result suggests paraphyly of the genus Parapodisma, endemic to Japan and adjacent regions. Chromosome number possibly changed at least twice in Podismini. Phylogenetic relationships among Parapodisma species are inferred on the basis of morphology using cladistic methodology. The result suggests that speciation in this genus occurred almost allopatrically in 3 lineages. All the 22 species of 9 genera of Japanese Podismini are described based on the above discussion. © 2015, Graduate School of Agriculture, Hokkaido University. All rights reserved.


Nakatake Y.,Regional Environmental Planning Inc. | Takamura N.,Japan National Institute of Environmental Studies | Saji A.,Japan National Institute of Environmental Studies | Saji A.,Katayama Chemical Inc. | And 2 more authors.
Ecology and Civil Engineering | Year: 2011

The effects of shrimp (Palaemon paucidens) on water quality and the zooplankton community were investigated by using eight enclosures in a restoration experiment pond of the Inbanuma Fishermen Cooperative Association in Kitasuga, Narita, Chiba (Japan). In shrimp enclosures, NH4-N, total nitrogen (TN), and chlorophyll a (Chl a) concentrations increased soon after the start of the experiment, indicating shrimp excretion and bioturbation caused increased NH 4-N, TN, and Chl a concentrations. Suspended solids (SS), TN, total phosphorus (TP), Chl a, and dissolved organic carbon (DOC) were significantly higher (P < 0.001) when shrimp were present. The total density of cladocerans and rotifers decreased significantly when shrimp were present but increased in the absence of shrimp. Among cladocerans, total densities of Daphnia, Diaphanosoma, and Scapholeberis decreased significantly (P < 0.05) when shrimp were present; however, the densities of Alona and Chydorus, which are small-sized benthic animals, did not differ significantly in the presence or absence of shrimp. The results of this study show that the presence of shrimp decreased water quality because nutrient recycling was accelerated by shrimp excretion and bioturbation, in addition to the trophic cascade effects, i. e. zooplankton community structure changes from shrimp through feeding on large cladocerans.

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