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Parapatric distributions of closely related species are common in many taxonomic groups. However, habitat overlap in sympatric areas within both species' ranges is complex and driven by the nature of the interactions between species as well as each species' ecological requirements. We therefore investigated the distribution of breeding habitats for two congeneric frogs, Pelophylax nigromaculatus and Pelophylax porosus brevipodus, in a region of Japan where these species co-occur, based on observation of mating calls as an index of the abundance of males engaging in reproductive activities. Among a total of 381 surveyed sites, P. nigromaculatus and P. porosus brevipodus were found at 171 and 229 sites, respectively. Pelophylax porosus brevipodus was widely distributed throughout the study area and was more abundant than P. nigromaculatus in sympatric sites. Analysis using cumulative link mixed models revealed that the abundance of calling males was negatively affected by the presence of calling males of the other species and by landscape factors. Interspecific differences in this negative effect appear to favor P. porosus brevipodus over P. nigromaculatus in our study area. Due to differences in the primary habitat preferences of the two species during the non-breeding season, habitat partitioning during the breeding season is likely driven by negative interspecific interactions during the reproductive process (i.e., reproductive interference). [ABSTRACT FROM AUTHOR]

In Japan, farm ponds retain water throughout the year while rice fields are continuously inundated for no more than 2 months, usually from spring to early summer. Although the zooplankton fauna in artificial water bodies would be expected to vary according to differences in inundation periods, scientific confirmation of this relation is largely lacking. Due to its ubiquity, the cladoceran Moina is a suitable target for studying habitat-related differences in the planktonic fauna, but its taxonomy remains unresolved, making morphological identifications potentially uncertain. We thus applied integrative taxonomy with both morphological and genetic evaluations for reliable species delimitation to Moina samples collected primarily in Japan (with smaller collections from Taiwan). This approach increased the alpha diversity of Moina species in Japan from three (in previous studies) to seven. It also revealed different habitat preferences among Moina species, with the smaller species being distributed mostly in farm ponds (followed by natural lakes), and the larger species mostly in rice fields. We argue that the phenological match/mismatch with inundation period of rice fields was a major factor for this strong trend of spatial species turnover, with differing degrees of fish predation pressure among the habitat types being another factor. [ABSTRACT FROM AUTHOR]

The article discusses the presence of birds in the rice fields of Korea and Japan. Rice is a major staple in Korea and Japan and 54% and 36% of their agricultural lands respectively are planted with the crop. 135 species of 430 native birds use the rice fields as foraging habitat, providing food for migratory and resident avian species. Most waterbirds prefer wide open rice fields for breeding. The population of waterbirds that consume fish or grain are said to be stable while the meat and insect eating kinds are decreasing.

Abstract: A high proportion of threatened and near-threatened species in the world now inhabit farmland. Although much data regarding the impact of agriculture on farmland biodiversity have been accumulated in Western countries, such information, particularly on the impact of rice cultivation, is fragmentary in other parts of the world and has rarely been disseminated internationally. Therefore, this paper aims to clarify what information has become available through earlier studies in Japan, where farmland mainly consists of rice paddy areas, and give directions for future studies about the impact of agriculture on farmland birds in Japan. This study made three notable observations. First, a review of earlier studies of farmland bird species in Japan uncovered some evidence of both increases (e.g., wildfowl and cranes) and declines (e.g., waders) in population size. Second, this paper closely examined case studies of two types of typical farmland birds: (1) geese and cranes foraging on crops and/or harvested remains of crops and (2) waders and egrets foraging on small organisms in farmland, not agricultural crops. This portion of the study identified some potential routes through which human activities in farmland affect bird species in Japan, and offered practical implications for conservation and management of these species supported by scientific data. Finally, based on the results of this review, three key tasks for future conservation studies and practices in Japanese farmland were suggested: (1) establishing quantitative indices based on monitoring surveys in farmland to track the population status, (2) collecting further evidence of the impact of agriculture, particularly on population-level responses by birds, and in a food-web context, and (3) applying evidence-based conservation to practice. [Copyright &y& Elsevier]

Spawning activity of the catfish, Silurus asotus, takes place in temporary water (rice fields) from early evening to midnight, generally in connection with rainfall, from late April to late August. Spawning of the catfish was correlated with hydrographic parameters dependent on rainfall: daily precipitation, turbidity, water depth, and water temperature. The spawning habits of the catfish, and in particular the use of temporary waters such as rice fields that become submerged after rainfall or by irrigation, are presumed to be adaptations to the Asian monsoon climate with a pronounced rainy season. The apparent sex ratio of the catfish was extremely biased toward females. Intraspecific variation in the reproductive ecology, particularly mating behavior, of this species is observed among local populations. Factors that may have caused this variation are discussed in the context of a comparison of mating behavior, reproductive environment, and sex ratio between the Lake Biwa population of S. Asotus and other conspecific populations, as well as two other species of silurid catfish that occur in the Lake Biwa drainage, S. Biwaensis and S. Lithophilus. [ABSTRACT FROM AUTHOR]

Flooded rice fields, which occupy half of the total agricultural land in Japan, are known to be foraging habitats for waterbirds. We investigated the use of various fallow fields by birds in midsummer, when rice fields are generally full of grown rice plants and are of little use for foraging waterbirds. We distinguished four types of fallow fields based on the ground cover and vegetation: (i) tall-grass fields; (ii) wet short-grass fields; (iii) dry fields; and (iv) flooded open fields. In August 1998 we counted birds four times in 19 survey plots of fallow fields and in seven plots of rice fields in Ibaraki Prefecture, Japan, where 82% of the farmlands are devoted to rice production. We observed 590 individual birds of 22 species, of which 15 species were waterbirds, mostly herons and shorebirds. Flooded open fields supported the largest number of species and the highest bird density, while rice fields supported the fewest. Within flooded open fields, herons preferred open-water areas, while shorebirds used bare ground most often. Wet short-grass fields looked similar to flooded open fields, except for the amount of short grass, but supported far fewer birds than flooded open fields. The number of birds in dry fields was comparable to that in flooded open fields, but most of the birds were ground-foraging passerines. Our limited dataset suggests that fallow fields can serve as valuable supplemental habitats for waterbirds during summer, if they are appropriately managed to preserve flooded open fields and smaller areas of other habitats. [ABSTRACT FROM AUTHOR]

Farmland abandonment can be a significant driver of biodiversity change in many parts of the world. Knowledge of the ecological impact of farmland abandonment at the landscape scale is particularly limited in Asia. We investigated how rice-field abandonment impacts bird diversity (i.e., species richness and composition) during the breeding and wintering seasons. Birds were surveyed in 31 grids (1 × 1 km) in rice ecosystems in central Japan, 16 of which were dominated by farmland while the others were surrounded by woodland. In each landscape type, survey grids were selected to ensure a broad range of abandonment rates, from fully cultivated to largely abandoned sites. Multi-species occupancy models showed that occupancy probabilities were associated with linear and quadratic terms of the abandonment rate, resulting in the highest predicted community-level occupancies and species richness at moderate abandonment rates (51.5–71%, depending on the season and surrounding landscapes, with the highest percentage in woodland landscapes in winter). Community composition was most associated with surrounding landscapes (i.e., woodland or farmland), followed by the abandonment rate. These results indicate the importance of habitat heterogeneity, related to moderate levels of farmland abandonment, in enhancing bird diversity in both farmland and woodland landscapes. Our findings illustrate the necessity for quantitative measures of farmland abandonment at landscape scales for understanding their nonlinear effects on farmland biodiversity. We suggest that agri-environmental schemes should consider the benefits of enhancing farmland mosaics at landscape scales, especially for small-scale farming in areas where farmland abandonment is increasing. • Bird occupancy and richness were highest at moderate abandonment rates. • Community compositions also changed with the abandonment rate. • Surrounding landscape and season affected the responses of birds. • Mosaics of managed and abandoned rice fields can benefit bird richness. [ABSTRACT FROM AUTHOR]

Neonicotinoids and fipronil are the most widely used insecticides in the world. Previous studies showed that these compounds have high toxicity to a wide taxonomic range of non-target invertebrates. In rice cultivation, they are frequently used for nursery-box treatment of rice seedlings. The use of fipronil and neonicotinoid imidacloprid is suspected to be the main cause of population declines of red dragonflies, in particular Sympetrum frequens, because they have high lethal toxicity to dragonfly nymphs and the timing of the insecticides' introduction in Japan (i.e., the late 1990s) overlapped with the sharp population declines. However, a causal link between application of these insecticides and population declines of the dragonflies remains unclear. Therefore, we estimated the amount of the insecticides applied for nursery-box treatment of rice seedlings and analyzed currently available information to evaluate the causality between fipronil and imidacloprid usage and population decline of S. frequens using Hill's causality criteria. Based on our scoring of Hill's nine criteria, the strongest lines of evidence were strength, plausibility, and coherence, whereas the weakest were temporality and biological gradient. We conclude that the use of these insecticides, particularly fipronil, was a major cause of the declines of S. frequens in Japan in the 1990s, with a high degree of certainty. The existing information and our analyses, however, do not allow us to exclude the possibility that some agronomic practices (e.g., midsummer drainage or crop rotation) that can severely limit the survival of aquatic nymphs also played a role in the dragonfly's decline.