Passive acoustic monitoring (PAM) has recently been developed and used for long-term and/or large spatial scale surveys. PAM is expected to be one of the most efficient methods for assessing species distribution and examining the factors affect it, helping identify important areas for biodiversity conservation and inform the management plan. In this study, we tested the feasibility of the PAM for monitoring bird species and revealed some critical points to consider in improving or developing more widely applicable PAM. We conducted PAM in the subtropical forest landscape of Amami-Oshima Island, Japan, which harbors rich biodiversity (over 100 species), including endangered and/or endemic plants and animals. Nine endemic forest bird species were detected across recording locations. The effects of environmental factors on the four bird species were analyzed, excluding the five species that were commonly detected and did not require occupancy modeling. Different environmental factors influenced the occupancy probability of the four species examined according to their habitat preferences, which is consistent with previous studies. Our results suggest that the combination of PAM and occupancy model enables us to identify the bird's spatial occupancy pattern, associated environmental factors, and the important areas that should be protected for conservation. PAM is a relatively low-cost and non-invasive method that can be applied in various monitoring of biodiversity conservation areas.

Frogs are a representative taxon that use advertisement calls to aid in reproduction. In most frog species, calls vary with body size, and allometric constraints between body size and call frequency have been widely reported among anuran species. Although this variation is an important driver of sexual selection in frogs, male advertisement call strategies may also vary according to body size. In this study, we conducted playback experiments on the male forest green tree frog ( Zhangixalus arboreus ) to determine whether male advertisement call characteristics and strategies vary according to body size and the amplitude of intraspecific chorus noise. The results indicated that the calls of larger individuals are louder and lower than those of smaller ones, who call more frequently; moreover, the calls become lower, and the number of calls decreases, as noise levels increase. These findings suggest that forest green tree frog emits lower calls or refrains from calling when chorus noise increases, and that intraspecific variation in advertisement call characteristics can induce different strategies in response to chorus noise. Because advertisement call variation with body size is common among frog species, intraspecific variation in male advertisement call strategies may also be a common phenomenon.

We tested a hypothesis regarding species commonness using a database compiled by a citizen science program called “Tokyo Butterfly Monitoring.” The data used were more than 34,000 butterfly records, which were cleansed through expert check after posted by monitoring participants from 2009 to 2017. We hypothesized that butterfly species with multiple annual reproductive cycles and food plants common in city environments are more common and would have more monitoring reports. The generalized linear mixed model (GLMM) analysis revealed significant effects of including “cultivated plants” in the larval food menu and “multivoltinism” on the number of individual species reported, which was compatible with the hypothesis. The species with the most records (12% of all records among 90 species) was Zizeeria maha , which reproduces 5–6 times annually and relies on Oxalis corniculata , a small weed common in urban open spaces. Argyreus hyperbius , a southern species that was very rare before the 1990s, ranked third in the current data. Its major host plant is a common garden plant, the pansy, which grows in most gardens and green spaces. The data collected by the monitoring program appear to represent the status of the butterfly community in Tokyo, a megacity subjected to rapid environmental changes.

Apis cerana japonica Radoszkowski population on Amami Island is thought to be hereditarily isolated from the mainland population. On Amami Island, the absence of a major mainland predator, Vespa mandarinia japonica Radoszkowski, which mass-attacks various social bees and wasps, is another marked difference. In this paper, we preliminarily report the possibility of Vespa analis eisa Yamane as an influential natural enemy according to beekeepers' observations, photographs and video recording on the attack of Vespa analis eisa and the subsequent formation of bee defensive balls (14 times). The body-size ratio of Vespa analis eisa to Amami A. cerana was more similar to that of V. mandarinia to mainland A. cerana, than it was to that of Vespa analis insularis Dalla Torre to mainland A. cerana. Furthermore, V. analis colonies on Amami had larger colonies than on the mainland. Overall, it appears that V. analis eisa is a potential predator of A. cerana, though more information on the ecological relationship between these species is needed before a firm conclusion can be drawn.

Glossy, broad‐leaved, evergreen (lucidophyllous) forests are found mainly in humid subtropical regions of East Asia and are recognized as a biodiverse biome harbouring numerous endemic species. To date, however, few studies have considered the conservation importance of rivers draining these unique environments. In this study, lotic Odonata were used as indicators to examine factors affecting riparian forest–stream linkages in a lucidophyllous forest in south‐western Japan. Lotic odonates of 10 species, including seven endemic species, and their habitats were studied along 30 stream reaches with varying environmental characteristics. Odonate species richness was greatest in shadier reaches as well as in heterogeneous locations in larger streams. In contrast, larger streams modified by channel enlargement for flood control had few or no odonate species. Protecting larger streams with less human impact and streams in dense riparian forest are the best options for conserving lotic odonates and their habitats in this globally unique forest type.

本研究では，二次林を含めた森林面積が島の約80％を占める奄美大島において，準絶滅危惧種に指定されているリュウキュウコノハズクの巣立ちビナのルートセンサスを，繁殖期（2017年6月27日–7月25日）に行なった．奄美大島のほぼ全域の合計58地点において98羽の巣立ちビナが確認され，うち13地点では複数回巣立ちビナが確認された．巣立ちビナ確認地点（53地点）と，確認地点と同頻度になるように各センサスルート上に無作為に設定した未確認地点（54地点）について，森林植生タイプ別の面積（常緑広葉樹林，常緑広葉樹二次林，常緑針葉樹林，落葉広葉樹二次林），開放地面積，林縁長，市街地までの距離，標高を説明変数として，一般化線形混合モデルを作成した．その結果，巣立ちビナの確認／未確認に対して常緑広葉樹林面積が正の効果を及ぼしていることが示された．今では限られた面積でしか存在しない成熟した亜熱帯常緑広葉樹林は，樹洞を有する大径木が多く存在し，本種の重要な営巣場所や繁殖場所となっている可能性が示唆された．

Previously, we observed several instances in which Apis cerana japonica performed dancing around the hive entrance and smeared plant materials there immediately after scouting of Vespa mandarinia japonica. In this study, we conducted a series of attack simulation experiments with three hornet species to investigate whether the hive entrance dance is a specific response to V. m. japonica scouting. We also tracked dancing bees and dance-follower bees to observe whether they perform hive entrance smearing. Only V. m. japonica scouting induced dancing, and we confirmed that dancing and dance-follower bees performed smearing behavior at the hive entrance. These results suggest that the hive entrance dance informs nest-mates of a specific emergency and of the urgent need to collect odorous plant materials as a counter-attack strategy.

We successfully discriminated wild and cultured anguillid eels without artificial tagging. For the purpose of population restoration of anguillid eels, stocking has been widely conducted in the European Union (EU) and Japan, although the net benefits of stocking remain unclear. To evaluate the effectiveness of eel stocking for population restoration, the survival, growth, escapement, and reproduction of stocked eels should be tracked. In this study, we explored the potential of using otolith oxygen and carbon stable isotope ratios as a natural tag to discriminate between wild and cultured eels, because cultured eels are often stocked into natural rivers and lakes. A discrimination model was developed based on wild (n = 95) and cultured (n = 314) Japanese eels as a training dataset. The results of accuracy estimation based on leave-one-out cross-validation were 96.8%. We then tested the applicability of the model to stocked-recaptured eels (n = 20); 100.0% were successfully identified as cultured eels, indicating that these eels spend their early continental phase in aquaculture ponds before stocking. This method could be widely applied to assess the effectiveness of eel stocking by determining the proportion of stocked eels among those captured from rivers, coastal areas, or spawning grounds.

Apis cerana japonica Radoszkowski, endemic to Japan, is known to be one of the most important pollinators for wild plants and crops, such as buckwheat, in cool to warm temperate Japan. To determine the degree of dependence of A. cerana japonica on forest resources, we analyzed pollen brought back to nests in a typical "Satoyama" landscape with relatively high deciduous forest coverage in northern Japan. We divided the landscape elements of the study area into three types: deciduous forest, conifer plantation and open land according to landcover digital data, and each pollen taxon was assigned to one of these three types of landscape elements. We collected total pollen loads of 15.75 g (total of colonies A and B) in May (spring), 1.57g ( total of colonies A and C) in June (early summer), 19.03 g (total of colonies A, B and C) in July (mid-summer) and 45.61 g (total of colonies A, B and D) in September (autumn). Deciduous forests are the most important foraging habitats for A. cerana japonica in the "Satoyama" landscape especially from spring to mid-summer when mass flowering of tall trees and shrubs species provides rich floral resources for developing bee colonies. On the other hand, the bees frequently foraged from herbaceous plant species in autumn when flowering of tree species reduces and herbaceous plant species have flowering peaks. In turn, the bees provide pollination services to a number of wild flowers blooming in various forest layers ranging from the canopy to the understory layer.

We investigated Odonata faunal and habitat characteristics (forest cover, emergent, submerged, floating-leaved and floating plant covers, pond area, NO3 −, chemical oxygen demand, and presence/absence of a nonnative fish) in 10 ponds on Amami-Oshima Island. In total, 26 species of six odonate families were found, and we detected significant nestedness of species composition among the ponds (22 species in the most species-rich pond, and 8 species in the most species-poor pond). Species found only in the most species-rich ponds were: Anax nigrofasciatus nigrofasciatus, Acisoma panorpoides panorpoides, Agriocnemis famina oryzae, Rhyothemis severini, Anasiaeschna martini, Hemicordulia okinawaensis, Lyriothemis elegantissima, and Hydrobasileus croceus (hereafter referred to as the rare species). These rare species are generally known to preferentially inhabit ponds with lush emergent plants and/or to prefer cooler habitats shaded by forest cover, such as Anax nigrofasciatus nigrofasciatus, Anac. martini, He. okinawaensis, and L. elegantissima. In contrast, the common species also found in species-poor ponds were: Ischnura senegalensis, Pantala flavescens, Anax parthenope julis, Ictinogomphus pertinax, and Tramea verginia, which are known to prefer an open water surface as spawning habitat. These differences in habitat preference between the rare and common species may be among the major reasons for the significant positive effects of percent forest cover and emergent plants on Odonata species richness. These results suggest that nestedness helped identify precise habitat characteristics and rare species that should be considered for conservation and restoration of lentic habitats on Amami-Oshima Island.

Forest patches characterized by old trees with large crown sizes are of high biodiversity conservation value because they contain various microhabitats and may preserve the original flora of primeval or ancient forests. Aerial photo estimations of the average tree crown size represent a promising approach for identifying and monitoring such forest patches. Numerous sensors and algorithms have been developed to estimate the crown size in coniferous forests or forests with relatively low topographic variations; however, methods for estimating the crown size in steep broad-leaved forests in tropical or temperate regions are still required. We propose a method of estimating the size of tree crowns to obtain the “crown size index (CSI),” which can be used as a candidate biodiversity index for steep broad-leaved forest patches. We applied this method to a subtropical broad-leaved forest in southwestern Japan. In the first step, gray values from aerial imagery are converted to relative values, and then the crown size is subjected to a granulometric estimation. Regression of the CSI from the diameter at breast height of the canopy layer trees presented R2 values as high as 0.67. Resampling tests revealed that monochrome aerial images resampled with spatial resolutions ranging from 0.40 m to 1.20 m produced results with relatively high accuracy (R2 ≥ .55). These results suggest that the proposed method has the potential for use as a cost-effective method of evaluating the biodiversity of broad-leaved forest patches in hilly or mountainous regions using images from various high-resolution sensors.

The honeybee species native to two remote islands (Amami-Oshima and Tsushima) in Japan were previously reported to be morphologically distinct from the Japanese honeybee Apis cerana japonica. To our knowledge, this is the first study to analyze the complete mitochondrial genome of the honeybee species from the two islands. The mitochondrial genome was a circular and approximately 1.5 kbp molecule that included 13 protein-cording genes (PCGs), 22 tRNA genes, 2 rRNA genes, and 1 AT-rich control region. The average AT content of the mitochondrial genome was 84%. The genetic distance suggested that the honeybee species from the two remote islands were more closely related to A. cerana japonica, among the A. cerana subspecies. Although the mitochondrial genome of the honeybee species from the two remote islands showed genetic variation distinct from those found in the A. cerana group, they were classified as the Japanese honeybee A. cerana japonica.

Citizen science has a long history in the ecological sciences and has made substantial contributions to science, education, and society. Developments in information technology during the last few decades have created new opportunities for citizen science to engage ever larger audiences of volunteers to help address some of ecology's most pressing issues, such as global environmental change. Using online tools, volunteers can find projects that match their interests and learn the skills and protocols required to develop questions, collect data, submit data, and help process and analyze data online. Citizen science has become increasingly important for its ability to engage large numbers of volunteers to generate observations at scales or resolutions unattainable by individual researchers. As a coupled natural and human approach, citizen science can also help researchers access local knowledge and implement conservation projects that might be impossible otherwise. In Japan, however, the value of citizen science to science and society is still underappreciated. Here we present case studies of citizen science in Japan, the United States, and the United Kingdom, and describe how citizen science is used to tackle key questions in ecology and conservation, including spatial and macro-ecology, management of threatened and invasive species, and monitoring of biodiversity. We also discuss the importance of data quality, volunteer recruitment, program evaluation, and the integration of science and human systems in citizen science projects. Finally, we outline some of the primary challenges facing citizen science and its future.

Japanese black bears often break branches when climbing trees and feeding on fruit in canopies, thereby creating small canopy gaps. However, the role of black bear-created canopy gaps has not been evaluated in the context of multiple forest dynamics. Our hypothesis was that small canopy gaps created by black bears improve light conditions, which facilitates fruiting of adult fleshy-fruited plants located beneath the gaps, and also that this chain interaction depends on interactions among the size of gaps, improved light conditions, forest layers, and life form of plants. The rPPFD, size of black bear-created canopy gaps, and fruiting/non-fruiting of fleshy-fruited plants were investigated in five forest layers beneath black-bear-created canopy gaps and closed canopies of Mongolian oak (Quercus crispula). We found that light conditions improved beneath black bear-disturbed trees with canopy gaps of large size, and the effect of improvement of light conditions was reduced with descending forest layers. Fruiting of fleshy-fruited plants, especially woody lianas and trees, was facilitated by the improvement of light conditions accompanied by an increase in the size of black-bear-created gaps. Data from this study revealed that canopy disturbance by black bears was key for improving light conditions and accelerating fruiting of fleshy-fruited trees and woody lianas in the canopy layers in particular. Therefore, our hypothesis was mostly supported. Our results provide evidence that Japanese black bears have high potential as ecosystem engineers that increase the availability of resources (light and fruit in this study) to other species by causing physical state changes in biotic materials (branches of Q. crispula in this study).

To reveal the influence of traditional management measures on the growth of Ischaemum aristatum var. glaucum, whose facilitation effects on plant species diversity have been addressed in our previous studies, experimental winter-mowing and burning treatments were implemented in Ukishima Marsh, a conservationally important freshwater lowland reed marsh of eastern Japan. Comparison of environmental conditions among burnt, mown, and control zones revealed that winter burning, which was even more effective than mowing, created well-illuminated conditions, a high cumulative ground-surface temperature, and a wide range of daily temperature fluctuations. Relative growth rates of I. aristatum var. glaucum shoots and individuals showed a significantly ascending gradient in the order of control, mown, and burnt zones. Continuation of traditional vegetation usage and management is recommended for Ukishima Marsh, as such methods would not only provide favorable environmental conditions for native herbaceous plants commonly, but would also indirectly maintain plant species diversity through promotion of plant facilitation as demonstrated in our previous studies.

Factors affecting the within-lake distribution of Trapa japonica were analysed in Lake Mikata, Japan, by integrating remote sensing analyses, field surveys, and laboratory experiments. The T. japonica bed has been expanding since 2006 and covered more than 60 % of the lake's area from 2008 to 2010. However, two parts of the lake, the upper and lower areas, retained open water, even during recent years. A survey of lake-bottom sediments revealed a heterogeneous seed distribution. Although seed density exceeded 13 seeds/m(2) in the lake's central area, no seeds were observed in the upper and lower areas. A seed-bag retrieval experiment showed that 75.6 % of seeds at the upper site germinated when seeds were artificially introduced, whereas 6.7 % of seeds germinated at the lower site. These results suggest that seed dispersal opportunities are the primary limitation on the distribution of T. japonica in the upper area. Brackish water was found in springs in the lower area, reflecting an adverse inflow of water from a downstream brackish lake. Laboratory experiments revealed significant adverse effects of water salinity on germination and early growth of T. japonica. Based on these results, we concluded that the heterogeneous distribution of T. japonica within the lake was determined by a combination of two factors: limitations on seed dispersal determined by the inflowing river and harmful salinity levels caused by inflows of seawater from the Sea of Japan via a downstream brackish lake.

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.

Unidirectional water flow results in the downstream-biased, asymmetric dispersal of many riverine organisms. However, little is known of how asymmetric dispersal influences riverine population structure and dynamics, limiting our ability to properly manage riverine organisms. A metapopulation of the freshwater pearl mussel Margaritifera laevis may be sensitive to river currents because mussels are repeatedly exposed to downstream drift during floods-a parasitic life stage is the only, limited period (similar to 40 days) during which larvae (glochidia) can move upstream with the aid of host fish. We hypothesized that water-mediated dispersal would overwhelm upstream dispersal via host fish, and therefore, that upstream subpopulations play a critical role as immigrant sources. To test this hypothesis, we examined the effects of both up-and downstream immigrant sources on the size of target subpopulations in the Shubuto River system, Hokkaido, Japan. We found that target subpopulation size was dependent on the upstream distribution range of reproductive subpopulations and the number of upstream tributaries, which are proxies for the number of potential immigrants moving downstream. In contrast, little influence was observed of downstream immigrant sources (proximity to downstream reproductive subpopulations). These results were consistent even after accounting for local environments and stream size. Our finding suggests that upstream subpopulations can be disproportionately important as immigrant sources when dispersal is strongly asymmetric.