記述言語：英語   掲載種別：研究論文（大学，研究機関等紀要）   出版者・発行元：国立大学法人帯広畜産大学  

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担当区分：最終著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：Regional Euro-Asian Biological Invasions Centre Oy (REABIC)  

DOI： 10.3391/mbi.2020.11.2.09

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1126/sciadv.aax0121

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.cropro.2019.02.002

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1093/beheco/ary125

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1073/pnas.1800042115

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Netherlands  

Detecting dispersal pathways is important both for understanding species range expansion and for managing nuisance species. However, direct detection is difficult. Here, we propose detecting these crucial pathways using a virtual ecology approach, simulating species dynamics using models, and virtual observations. As a case study, we developed a dispersal model based on cellular automata for the pest insect Stenotus rubrovittatus and simulated its expansion. We tested models for species expansion based on four landscape parameters as candidate pathways
these are river density, road density, area of paddy fields, and area of abandoned farmland, and validated their accuracy. We found that both road density and abandoned area models had prediction accuracy. The simulation requires simple data only to have predictive power, allowing for fast modeling and swift establishment of management plans.

DOI： 10.1007/s13280-018-1026-y

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier GmbH  

Environmental fluctuations can influence invertebrate population dynamics over large spatial scales, and effects of climate change are of particular importance in understanding phenology. In this study, we tested whether changing climate patterns could increase voltinism and emergence synchrony in Stenotus rubrovittatus and drive the mirid bug's expansion into currently uninhabited areas of Japan. This expansion could have potentially serious economic consequences for the rice industry. We modelled development of S. rubrovittatus in the field applying the effective accumulated temperature model to calculate the theoretical number of generations and the egg hatching dates from 2003 to 2012 based on a high-resolution, daily weather database. We then performed a regional analysis to assess the relationship between population dynamics and range expansion across the study region and also included a local analysis to evaluate how population parameters affect the presence of S. rubrovittatus at local sites in each year. Results showed that distribution expanded with a relative increase in voltinism and with synchrony of egg hatching date. Moreover, we showed that increased voltinism in the previous year positively influenced local population occurrence. This positive effect suggests that the species’ distribution range expands through increased reproduction at both the regional and local scale. Climate-mediated population dynamics play a significant role in range expansion of the mirid bug.

DOI： 10.1016/j.baae.2018.05.006

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/jzo.12479

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：[日本生態学会] 保全生態学研究編集委員会  

DOI： 10.18960/hozen.22.1_63

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：獣医疫学会  

Raccoons (Procyon lotor), intermediate hosts of Toxoplasma gondii (T. gondii), utilize a variety of environments, so they are thought to be good indicators of the presence of T. gondii oocysts in their habitat. In this study, a serological survey of T. gondii was conducted in raccoons captured between 2010 and 2014 in rural areas of the Tokachi district, Hokkaido, Japan to estimate environmental factors associated with T. gondii prevalence. Antibodies were detected from 9.4% (10/107) with latex agglutination tests. Logistic mixed regression models showed that total river length (km) in raccoon habitats was associated positively with T. gondii seropositivity (OR＝14.67, 95% CI＝2.64—81.58). Cats (Felis silvestris catus) are natural hosts of T. gondii, and together with raccoons they share riverside environments. In such areas where humans do not remove trash and animal feces, raccoons might easily be exposed to matured oocysts. Environmental factors associated with T. gondii prevalence in raccoons could be important information to identify high risk areas for human T. gondii infection. Our present result was also useful from the public health perspectives when considering the infection risk of T. gondii to humans.

DOI： 10.2743/jve.19.108

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その他リンク： https://jlc.jst.go.jp/DN/JLC/20020994813?from=CiNii

記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）   出版者・発行元：日本生物科学者協会 ; 1949-  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-BLACKWELL  

1. Landscapes in nature can be viewed as a continuum of small total habitable area with high fragmentation to widely spreading habitats. The dispersal-mediated rescue effect predominates in the former landscapes, while classical density-dependent processes generally prevail in widely spread habitats. A similar principle should be applied to populations of organisms utilizing microhabitats in limited supply.
2. To test this hypothesis, we examined the population dynamics of a web spider, Neriene brongersmai, in 16 populations with varying degrees of microhabitat availability, and we explored whether: (i) high microhabitat availability improves survival rate during density-independent movement, while the resultant high density reduces survival rate in a densitydependent manner; and (ii) temporal population stability increases with microhabitat availability at the population level. Furthermore, we conducted two types of field experiments to verify whether high microhabitat availability actually reduces mortality associated with website movement.
3. Field observations revealed that demographic change in N. brongersmai populations was affected by three factors at different stages, namely the microhabitat limitation from the early to late juvenile stages, the density dependence from the late juvenile to adult stages and the food limitation from the adult to the next early juvenile stages. In addition, there was a tendency for a positive association between population stability and microhabitat availability at the population level.
4. A small-scale experiment, where the frequency of spider web relocation was equalized artificially, revealed that high microhabitat availability elevated the survival rate during a movement event between web-sites. The larger spatiotemporal scale experiment also revealed an improved spider survival rate following treatment with high microhabitat availability, even though spider density was kept at a relatively low level.
5. The population dynamics of N. brongersmai can be determined primarily by density-independent processes based on web-site fragmentation and density-dependent processes driven by interference competition. We conclude that depending on the amount of habitat resources, the relative importance of the two contrasting paradigms-equilibrium and non-equilibrium-appears to vary, even within a particular system.

DOI： 10.1111/1365-2656.12213

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS INC  

Non-native plant species can provide native generalist insects, including pests, with novel food and habitats. It is hypothesized that local and landscape-level abundances of non-native plants can affect the population size of generalist insects, although generalists are assumed to be less sensitive to habitat connectivity than specialists. In a heterogeneous landscape in Japan, the relationship between the density of a native pest of rice (Stenotus rubrovittatus (Matsumura) (Heteroptera: Miridae)) and the abundance of Italian ryegrass (Lolium multiflorum Lam. (Poales: Poaceae)), a non-native meadow grass known to facilitate S. rubrovittatus, was analyzed. Statistical analyses of data on bug density, vegetation, and the spatial distribution of fallow fields and meadows dominated by Italian ryegrass, obtained by field surveys, demonstrated that local and landscape-level abundances of Italian ryegrass (the unmowed meadow areas within a few hundred meters of a sampling plot) positively affected bug density before its immigration into rice fields. Our findings suggest that a generalist herbivorous insect that prefers non-native plants responds to spatial availability and connectivity of plant species patches at the metapopulation level. Fragmentation by selective mowing that decreases the total area of source populations and increases the isolation among them would be an effective and environmentally-friendly pest management method.

DOI： 10.1673/031.014.111

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER INTERNATIONAL PUBLISHING AG  

Winter-flooding of rice paddies without the application of agricultural chemicals is attracting attention as a new agricultural method for enhancing the habitat conditions of wintering waterfowl in rice paddy ecosystems throughout Japan and east Asia. Conditions in these paddies are expected to result in restoration of not only the winter habitats of waterfowl but also those of other taxonomic groups during the rice growing season. In this study, we tested whether the diversity of summer spiders-ubiquitous predators in rice paddies-was higher in the winter-flooded paddies than in the conventional ones by conducting field measurements in 31 winter-flooded and 7 conventional paddies. Limiting factors of spiders in the winter-flooded paddies were then examined. Results revealed that both the density and species richness of spiders were significantly higher in the winter-flooded paddies than in the conventional ones both before and after the insecticide application against pecky rice bug Stenotus rubrovittatus (Matsumura) (Hemiptera: Miridae) to conventional paddies. In addition, spider density and species richness in the winter-flooded paddies correlated with the availability of two prey groups-chironomids and other nematocera. These findings suggest that in the winter-flooded paddies the diversity of generalist predators is higher than in the conventional ones during the rice-growing season and that the combination of management at both the landscape and field level is likely more effective for increasing spider abundance in winter-flooded paddies.

DOI： 10.1186/2193-1801-3-418

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER HEIDELBERG  

Tree rubbing by brown bears (Ursus arctos) is a well-known behavior throughout the animal's distribution. There is still insufficient information on the characteristics and function of the behavior. We investigated seasonal frequency of tree rubbing by brown bears, characteristics and reasons for selection of rub trees, and characteristics of bear signs on and around rub trees in a mixed coniferous-broad-leaved deciduous forest in Hokkaido, Japan. Between 1998 and 2009, we found 172 rub trees and confirmed 995 tree rubbings. We found that the rub trees were used repeatedly by bears within a year and for multiple years (more than 10 years). Tree rubbing by brown bears was observed from April to November, with a peak between May and June that corresponds to the mating season of brown bears. Abies sachalinensis was selected and broad-leaved trees were avoided for tree rubbing based on estimated availability in natural forest. The preference for Abies sachalinensis might be because the strong odor of resin attracts bears for rubbing their head and neck in resinous substances and for increasing the detectability of their markings by receptor bears. Selected trees for rubbing were located right beside the trail on relatively level ground among trees along roads or trails. Trees had a relatively large diameter at breast height. These characteristics would also serve to increase the access and detectability of their markings. Series of pad-shaped depressions was the most frequently observed (70 %) indication of bear rubbing, followed by debarking (51 %) and clawing (30 %). In terms of visual and olfactory signal amplification, physical damage by bears to the trees might have a function to enhance the smell as a result of increase in outflow of the resin. We conclude that tree rubbing behavior is associated with the mating season of brown bears and that the main purpose of this behavior is scent marking to communicate intraspecifically during the mating season.

DOI： 10.1007/s13364-013-0143-z

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本哺乳類学会  

本研究では，北海道十勝地域において頻繁にロードキルが発生しているアカギツネVulpes vulpes（以下キツネ）を対象に，北海道開発局が収集した国道におけるロードキルデータを用いて，その発生数が道路の交通量や道路周辺の景観構造およびエゾシカ（Cervus nippon yesoensis，以下シカ）の駆除・狩猟から受ける影響を検討した．2000～2009年のキツネの国道におけるロードキルデータを2つの季節に分け，国道を2 km毎に区切ったトランセクト内のロードキル発生数を目的変数とした一般化線形モデルによる解析を行った．考慮した影響要因は，トランセクト内の平均交通量，トランセクトの中心から半径1 km内に含まれる市街地，草地，農耕地，森林の面積率，河川総延長，景観の多様度指数，シカの平均駆除数，平均狩猟数，シカの平均生息密度指標である．その結果，産仔・育仔期（3月～8月）のキツネのロードキル発生数は局所的な交通量とともに増加したがある一定の交通量を超えると減少し，さらに道路周辺に草地が多くシカの狩猟数が多い場所で多くなった．分散・交尾期（9月～2月）のキツネのロードキル発生数は景観の多様度指数が高く，かつシカの密度指標が低い場所で多かった．本研究により，十勝におけるキツネのロードキル発生数と関係のある要因は季節によって異なることが示され，またキツネと景観の多様度との関係性やキツネによるシカ狩猟残滓利用の可能性，シカがキツネへ与える間接効果の可能性などキツネの生態に関するさまざまな仮説が提示された．https://www.jstage.jst.go.jp/article/mammalianscience/53/2/53_301/_article/-char/ja/

DOI： 10.11238/mammalianscience.53.301

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

The effects of sika deer (Cervus nippon) browsing and understory productivity on web-building spiders' density were experimentally examined. We particularly focused on the nonlinear effects of these 2 factors and their underlying mechanisms. Our field experiments controlling deer density and understory productivity revealed that the deer affected the densities of 2 abundant spider species nonlinearly: the deer effect was unimodal or constant in lower productivity plots and negative in higher productivity plots. The nonlinear effects seemed to occur because the response trend of the spiders' limiting factors to deer impact differed between lower and higher productivity plots. In lower productivity plots, the density of the most abundant spider species, Prolinyphia longipedella, was limited by dicot cover, and both spider density and dicot cover had unimodal-shaped responses to deer density. This spider species was limited by the availability of twigs in higher productivity plots and responded negatively to deer density. Deer seemed to affect web-building spider density in understory vegetation by changing the number of available sites for webs through browsing. However, the precise limiting factors differed with understory productivity. Since forest understory productivity is expected to show large variation at various spatial scales due to differences in canopy tree density, the availability of nutrients, and other environmental factors, considering nonlinear effects is important when predicting the impact of large herbivores on invertebrates in forest understories.

DOI： 10.2980/20-1-3580

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER ARACHNOLOGICAL SOC  

Trait-mediated effects of predators can impact prey population dynamics by affecting prey behavior,. The mind bug Stenotus rubrovittatus (Matsumura) (Hemiptera: Miridae), a major insect pest in Japanese rice production, usually remains in the upper layer of paddies to feed on rice ears. However, the minds are frequently trapped by horizontal webs of Tetragnatha spp. spiders, which are highly abundant in organic rice paddies, and fall to the bottom layers of paddies where they are preyed upon by ground-dwelling predators. It is hypothesized that Tetragnatha spp. spiders facilitate bug predation by wolf spiders through trait-mediated effects, in which their horizontal Webs force the bugs onto or near the ground and thereby into the hunting zones of wolf spiders. Molecular gut-content analysis of 619 wolf spiders coupled with field measurements revealed that the number of wolf spiders that tested positive for mind bug predation increased significantly with the density of Tetragnatha spp. spiders in the paddies. We also observed a positive relationship between Tetragnatha spp. abundance and total cover by their webs in paddies. We identified the potential for an unexpected interaction between an herbivorous insect pest and ground-dwelling spiders that usually inhabit different microhabitats in paddy fields by focusing on trait-mediated effects of webs built by Tetragnatha spp. Because spider webs occupy a certain proportion of the available space in terrestrial ecosystems, consideration of trait-mediated effects on interactions between flying insects and other predators may lead to a better understanding of local food webs.

DOI： 10.1636/P12-30.1

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ACADEMIC PRESS INC ELSEVIER SCIENCE  

Mirid bugs, major insect pests in rice production, have dramatically expanded their range in Japan, resulting in increased economic losses especially for organic rice farmers. In this study, the within-field and landscape-scale factors affecting the bug and its damage to crops were examined in organic rice farms. Bug densities and crop damage levels showed significant positive relationships with weed densities (Schoenoplectus juncoides and Echinochloa crus-galli) within individual fields. Bug densities were negatively associated with Tetragnatha spp. and Pachygnatha clercki densities, indicating that these spiders act as biological control agents that help to decrease crop damage levels. At the landscape scale, bug densities increased with the proportion of the area that was fallow within a 400-m radius around focal fields. Fallows represent important source habitat for the bug and the spatial extent at which bug abundance was affected indicates the mobility of these insects. These results suggest that the combination of biological control by natural enemies, and weed management within individual paddies and surrounding landscapes inside a buffer zone of less than half a kilometre may be effective in controlling mirid bugs and the damage they cause in organic paddy fields. (C) 2011 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.biocontrol.2011.11.011

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ENTOMOLOGICAL SOC AMER  

Source populations of polyphagous pests often occur on host plants other than the economically damaged crop. We evaluated the contribution of patches of a non-native meadow grass, Lolium multiflorum Lam. (Poaceae), and other weeds growing in fallow fields or meadows as source hosts of an important native pest of rice, Stenotus rubrovittatus (Matsumura) (Hemiptera: Miridae), in an agricultural landscape of northern Japan. Periodical censuses of this mind bug by using the sweeping method, vegetation surveys, and statistical analysis revealed that L. multiflorum was the only plant species that was positively correlated with the density of adult S. rubrovittatus through two generations and thus may be the most stable and important host of the mind bug early in the season before the colonization of rice paddies. The risk and cost of such an indirect negative effect on a crop plant through facilitation of a native pest by a non-native plant in the agricultural landscape should not be overlooked.

DOI： 10.1603/EN11032

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER GMBH, URBAN & FISCHER VERLAG  

Spiders are common generalist predators, and understanding their potential in biological control is important for the development of integrated pest management programs. In this study, predation by three groups of spiders on the mind bug Stenotus rubrovittatus (Hemiptera: Miridae) in rice paddies was investigated using DNA-based gut-content analysis. A laboratory feeding study revealed that the detection half-lives of bug DNA in the spider gut at 25 degrees C was 3.4 days for Lycosidae and 1.5 days for Tetragnathidae. Individual spider predation on the mind bug was investigated by detecting DNA of prey in field-collected spiders. In total, 1199 spiders were assayed from three spider groups: Pirata subpiraticus (Lycosidae), Tetragnatha spp. (Tetra-gnathidae), and Pachygnatha clercki (Tetra-gnathidae), which each differ in their preferred microhabitat as well as their predatory habits. Detection rates of prey DNA in spiders increased significantly with the density of prey across all spider groups. P subpiraticus and Tetragnatha spp. predation showed a better fit to a saturated response curve to increasing prey density, while P. clercki showed a simple linear relationship with prey density. Densities of alternative prey species did not affect the detection rates of minds. These results suggest that predation on pests by generalist predators in an agroecosystem is affected not only by prey abundance but also by predator preference for specific prey. Predator preference is therefore an important factor to consider when estimating the role of natural enemies as biological control agents.

DOI： 10.1016/j.baae.2011.07.007

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本生態学会  

シカによる水稲被害が深刻化している千葉県房総半島南部において、約350軒の稲作農家を対象とした聞き取りアンケート調査から、シカによる水稲被害のレベルを定量化し、それをシカの局所密度と水田周辺の景観構造により説明する統計モデルを構築した。その結果、被害レベルはシカ密度に加え、対象水田から半径400m以内の景観構造により影響を受けていることが明らかになった。具体的には、水田周囲の森林率の増加に伴い被害は大きくなること、またシカの高密度地域では周辺景観の林縁長が長いと被害が軽減される傾向があることがわかった。この空間スケールは、既往研究から示された房総のシカの行動圏や食物の質、妊娠率が決まる空間スケールとほぼ一致していた。次に統計モデルを用いて被害が軽度に維持されるシカ密度をシカ分布域とその周辺を含めた地域で推定し、水稲被害のリスクマップを作成したところ、被害が軽度に維持されるシカ密度は地域の景観構造により大きく異なることがわかった。異質な景観構造をもつ地域では、こうしたリスクマップと現在のシカ生息密度とを比較し、短期的な捕獲目標個体数を局所レベルで定めることで、被害防除努力をより効率的に配分することができるだろう。

DOI： 10.18960/hozen.15.2_203

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記述言語：日本語   掲載種別：研究論文（研究会，シンポジウム資料等）   出版者・発行元：関東雑草研究会  

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記述言語：英語  

We examined web-building spider species richness and abundance in forests across a deer density gradient to determine the effects of sika deer browsing on spiders among habitats and feeding guilds. Deer decreased the abundance of web-building spiders in understory vegetation but increased their abundance in the litter layer. Deer seemed to affect web-building spiders in the understory vegetation by reducing the number of sites for webs because vegetation complexity was positively correlated with spider density and negatively correlated with deer density. In contrast, the presence of vegetation just above the litter layer decreased the spider density, and deer exerted a negative effect on this vegetation, possibly resulting in an indirect positive effect on spider density. The vegetation just above the litter layer may be unsuitable as a scaffold for building webs if it is too flexible to serve as a reliable web support, and may even hinder spiders from building webs on litter. Alternatively, the negative effect of this vegetation on spiders in the litter may be as a result of reduced local prey availability under the leaves because of the reduced accessibility of aerial insects. The response to deer browsing on web-building spiders that inhabit the understory vegetation varied with feeding guild. Deer tended to affect web-invading spiders, which inhabit the webs of other spiders and steal prey, more heavily than other web-building spiders, probably because of the accumulated effects of habitat fragmentation through the trophic levels. Thus, the treatment of a particular higher-order taxon as a homogeneous group could result in misleading conclusions about the effects of mammalian herbivores.

DOI： 10.1603/0046-225X(2008)37[938:CROWST]2.0.CO;2

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PubMed

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.18960/hozen.13.1_65

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ECOLOGICAL SOCIETY OF AMERICA  

Although provisioning of habitat by ecosystem engineers is one of the most common biological interactions, previous studies have mostly focused on facilitative or bottom-up processes. Here we show that engineering effects can indirectly strengthen top-down effects mediated by predator abundance. We conducted a small-scale manipulative. field experiment and broad-scale. field observations of the plant, web spider, and detrital insect system in forest understory habitats. In the field experiment, artificially increasing architectural elements enhanced the abundance of spiders by providing physical support for web building. Moreover, aerial insects derived from the detrital food web decreased in response to increased spider abundance. As artificial architecture per se did not affect aerial detritivores, these results indicate that ecosystem engineering indirectly strengthens top-down effects mediated by predators. In field observations conducted in 12 cedar forests, path analyses supported the importance of an indirect pathway originating from understory vegetation complexity to spider abundance and to aerial detritivores. The effect size of spiders on detrital insects was similar in the field experiment and in the observations. These results indicate that the engineering effects of plants cascade to detrital insects through web spiders across different scales.

DOI： 10.1890/06-1633.1

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER JAPAN KK  

Evaluating the quality of wildlife habitat is essential for understanding and predicting population dynamics in heterogeneous environments. We used fecal nitrogen levels as an indicator of habitat quality of sika deer (Cervus nippon) and explored important landscape elements influencing nitrogen levels, taking deer density into account. We established 92 plots differing in deer density and landscape structure on the Boso Peninsula, central Japan, and collected fecal samples along a 1-km transect at each plot. The regression models involving two independent variables, i.e., deer density and the length of forest edge within an area of 100 or 200 m from the transect, were selected based on the Akaike's Information Criterion (AIC). Levels of fecal nitrogen were positively correlated with the length of the forest edge and negatively correlated with population density of deer. The area of 100 or 200 m from the transect most likely reflected the behavioral scale of the deer. Coverage of palatable understory vegetation increased with proximity to forest edge and decreased with deer density. Variability in the level of fecal nitrogen could thus be explained by food availability in the landscape. These results suggest that landscape alterations increase the carrying capacity of sika deer and thereby increase impacts upon the ecosystem.

DOI： 10.1007/s10144-007-0046-4

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER TOKYO  

We examined 15 populations of Neriene brongersmai, a common sheet-web spider inhabiting cedar forest floor, to find out how density at a small spatial scale (patch level) is determined by processes operating at this scale as well as those from a larger spatial scale (population level). Here we focus on two types of large-scale effects that may influence small-scale density: an additive effect that changes the density at patch level; and a non-additive effect that changes the relationship between the density and its limiting factor at the patch level. ANCOVA showed that patch-level density of this spider was positively correlated with web-site availability at this level, but the density with a given amount of web-site differed among populations (cedar forests), indicating the existence of an additive large-scale effect. Multiple regression analysis showed that web-site availability at a population level explained the additive large-scale effect well, but prey availability and forest size did not. It seemed likely that increased web-site availability may have reduced the mortality of spiders while moving to a new web-site, and hence increased population density. A non-additive large-scale effect was also revealed: i.e. the relationship between density and web-site availability at the patch level tended to be stronger in populations with a greater additive large-scale effect. Higher intraspecific competition for web-sites in these populations appeared to have strengthened this relationship.

DOI： 10.1007/s10144-004-0187-7

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：UNIVERSITE LAVAL  

We examined the abundance and species richness of web spiders in forests with and without deer to test the hypothesis that herbivory by deer simplifies habitat structure, thereby reducing the number of web spiders. The number of individuals, the number of species, and the availability of potential web sites were all lower where deer were present. The decrease in the abundance of spiders in the presence of deer was more prominent in large species. The species richness standardized by rarefaction was still lower where deer were present in one of two seasons, suggesting that the reduced number of species in the presence of deer was not simply a by-product of the decreased number of individuals. Web site availability was positively correlated with the number of individuals as well as with the number of species when both forest types were combined. However, prey availability, estimated by the number of insects captured with sticky traps, did not differ significantly between sites with and without deer. Thus, the decrease in spiders was most likely caused by indirect non-trophic effects of herbivory that were mediated by the simplification of habitat structure, not by a decrease in prey abundance.

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TAYLOR & FRANCIS  

We examined the defensive function of spines of Damnacanthus indicus against deer herbivory by experimentally removing spines in the field where deer density is high. Individuals of D. indicus whose spines had been removed had a higher probability of being browsed by deer than control individuals. In addition, plant height was significantly lower for individuals that were browsed than those that were not. These results support the notion that spines of D. indicus have a function to deter deer browsing. This study is the first to demonstrate experimentally the defensive function of spines against large mammals in temperate areas.

DOI： 10.1007/s10310-003-0043-1

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：BLACKWELL MUNKSGAARD  

Detrital infusion into grazing food web is considered to be important in terrestrial communities, but there is hardly any experimental evidence showing that generalist predators aboveground are sustained by belowground detritivores. We established two types of experimental plots in the forest floor, one with sheets on the ground to prevent the emergence of belowground arthropods and the other without sheet, to test the hypotheses that 1) reduced input of detrital arthropods decreases the abundance and species richness of web spiders (major generalist predators in terrestrial ecosystems) and 2) lower number of spiders increases the abundance of herbivorous arthropods. We found that spiders were less abundant in plots where the emergence of detrital arthropods was reduced, while the abundance of herbivores did not significantly increase in these plots. These results provide empirical evidence that organisms moving from underground to aboveground may be important for the maintenance of aboveground predators, although the cascading effect of predator abundance on the grazing food chain was not detected in the present study.

DOI： 10.1034/j.1600-0706.2003.12586.x

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER-VERLAG  

We demonstrated the effect of cross-habitat foraging by sika deer (Cervus nippon) on plant communities under the hypothesis that the intensity of herbivory on a plant community is changed by the presence of a preferable habitat for deer nearby. To investigate this landscape-level effect, we examined two types of forest understory; "adjacent site" was located near agricultural fields where deer prefer to forage, and "remote site" was far from fields. We compared plant community structures between adjacent and remote sites in areas with high deer densities, and found that plant species richness and plant coverage were significantly higher in adjacent sites than in remote sites. We hypothesized that this difference was caused by the lower intensity of browsing at adjacent sites due to the higher use of fields by the deer at these sites. The following four results supported this hypothesis. First, in areas with no deer, plant species richness and plant coverage did not differ significantly between adjacent and remote sites. Second, we demonstrated a lower intensity of herbivory at adjacent sites by experimentally transplanting a preferred plant species, Aucuba japonica. Third, we detected no difference in the number of deer fecal pellets found in adjacent and remote sites, indicating that the difference in browsing intensity between the two sites was not due to differences in the frequency of site use by the deer. Fourth, fecal analysis showed that deer at adjacent sites consumed more graminoids, suggesting that deer at these sites used fields to forage because graminoids were abundant in fields. All of these results support the notion that the intensity of herbivory on forest understorys becomes lower in the presence of agricultural fields nearby. This also implies the importance of the indirect effects at the landscape level in that the two ecosystems are linked by the consumers moving between them.

DOI： 10.1007/s00442-002-1037-y

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：BLACKWELL PUBLISHING ASIA  

We report here the possibility of an induced resistance of a spiny shrub Damnacanthus indicus against deer herbivory. Six characters of D. indicus were compared between regions with and without deer herbivory on the Boso Peninsula. We found that D. indicus in browsed areas produced smaller leaves, thicker spines, and shorter internode distances between spines than those in unbrowsed areas whereas the length of spines and the angle of a pair of spines did not differ significantly. It is likely that D. indicus shows an induced resistance by producing smaller leaves, and by increasing stoutness of spines and spine density.

DOI： 10.1046/j.1440-1703.2001.00436.x

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記述言語：日本語   会議種別：ポスター発表  

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記述言語：日本語   会議種別：口頭発表（一般）  

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記述言語：日本語   会議種別：シンポジウム・ワークショップ パネル（指名）  

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記述言語：英語   会議種別：ポスター発表  

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記述言語：日本語   会議種別：ポスター発表  

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記述言語：日本語   会議種別：ポスター発表  

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記述言語：日本語   会議種別：口頭発表（一般）  

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記述言語：日本語   会議種別：口頭発表（一般）  

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記述言語：日本語   会議種別：口頭発表（一般）  

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記述言語：日本語   会議種別：ポスター発表  

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記述言語：日本語   会議種別：口頭発表（一般）  

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記述言語：日本語   会議種別：ポスター発表  

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記述言語：日本語   会議種別：ポスター発表  

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記述言語：日本語  

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開催年月日： 2001年 　 　

記述言語：日本語  

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開催年月日： 2000年10月 - 　

記述言語：日本語  

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開催年月日： 2000年3月 - 　

記述言語：日本語  

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