Noriko IWAI | Tokyo University of Agriculture and Technology (original) (raw)

Papers by Noriko IWAI

Research paper thumbnail of Exploration of aversive bioacoustics for the effective management of invasive green anoles (Anolis carolinensis)

Journal for Nature Conservation

Research paper thumbnail of Larval food habits of the Forest Green Tree Frog

Bulletin of the Herpetological Society of Japan, 2005

Research paper thumbnail of Comparison of the detection of 3 endangered frog species by eDNA and acoustic surveys across 3 seasons

Freshwater Science, 2020

For conservation of endangered species, basic ecological information is indispensable. Environmen... more For conservation of endangered species, basic ecological information is indispensable. Environmental DNA (eDNA) is increasingly used to estimate the presence/absence of aquatic organisms such as frog species. However, the efficiency of detecting eDNA may depend on the ecological characteristics of the target frog species. Here, we adopted an eDNA approach for detecting 3 endangered Japanese species (Babina subaspera, Odorrana splendida, and O. amamiensis). We compared eDNA detection with a traditional acoustic survey method in 3 different seasons. Detection of species was not always consistent between the 2 methods, probably because acoustic surveys target only calling adult males but eDNA detects individuals of both sexes and at any life-history stage in water. Moreover, the differences in detection patterns between the 2 methods among species may be correlated with different characteristics of mating behavior (e.g., calling volume) and life history of tadpoles (e.g., migration ability). The optimal season for detection by eDNA method also differed between the 3 species, probably because of differences in breeding season and larval characteristics. We show that results obtained from eDNA detection methods and traditional field observation techniques, including acoustic surveys, are not always consistent with each other but rather depend on the ecological characteristics of the respective target species. It is therefore necessary to consider the ecological traits of frog species, such as breeding season and seasonal shifts in tadpole abundance, when applying eDNA methods for distribution surveys.

Research paper thumbnail of Shredder���tadpole facilitation of leaf litter decomposition in a tropical stream

Freshwater Biology, 2009

1. Leaf litter decomposition is one of the most important ecosystem processes in streams. Recent ... more 1. Leaf litter decomposition is one of the most important ecosystem processes in streams. Recent studies suggest that facilitation, in which litter is processed by a succession of species with differing abilities and requirements, may be important in making the nutrients bound in litter available to the stream assemblage. 2. We predicted that stream invertebrates that feed on terrestrial leaf litter (shredders) and tadpoles would facilitate leaf litter decomposition by changing the quality of leaf material directly via physical contact or indirectly via nutrient release. We experimentally examined the ability of shredders and tadpoles to break down leaves, independently and together, in artificial streams beside a natural forest stream. 3. The decomposition rate was greater when shredders and tadpoles were together than was expected from rates in single-species treatments, indicating that facilitation occurred. This facilitation operated in one direction only: the rate of leaf breakdown by tadpoles was higher when leaves had been partly processed by shredders, but there was no similar effect when leaves previously occupied by tadpoles were processed by shredders. We did not detect facilitation caused by indirect nutrient release. 4. Shredders may have benefited tadpoles by roughening leaf surfaces, making them easier for the tadpoles to consume and enhancing leaf breakdown in the presence of both taxa. This indicates that the loss of a single species can have impacts on ecosystem functioning that go beyond the loss of its direct contribution.

Research paper thumbnail of Can ecological stoichiometry help explain patterns of biological invasions?

Oikos, 2010

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Research paper thumbnail of Figure 2 from: Sato TC, Iwai N (2021) Choice of tree holes as oviposition sites by Kurixalus eiffingeri on Iriomote Island. Herpetozoa 34: 201-205. https://doi.org/10.3897/herpetozoa.34.e67271

Research paper thumbnail of Figure 3 from: Sato TC, Iwai N (2021) Choice of tree holes as oviposition sites by Kurixalus eiffingeri on Iriomote Island. Herpetozoa 34: 201-205. https://doi.org/10.3897/herpetozoa.34.e67271

Research paper thumbnail of Calling-Site Preferences of Three Co-occurring Endangered Frog Species on Amami-Oshima Island

Herpetologica

Abstract Hotspots of amphibian species diversity typically occur in limited geographical ranges, ... more Abstract Hotspots of amphibian species diversity typically occur in limited geographical ranges, and critically endangered habitats often contain a large number of endemic amphibian species. In such regions, it is prudent to engage conservation strategies for multiple amphibian species simultaneously. To correctly identify suitable habitats for multiple species, species interactions should be considered in species distribution models. In this study, we adopted a joint species distribution model to determine the abiotic and biotic factors that affect calling-site choice in three endangered co-occurring frog species on Amami-Oshima Island, and examined whether they co-occur more than expected after considering the overlapping preferences in environmental variables. Occurrences of Babina subaspera, Odorrana splendida, and O. amamiensis were assessed by monitoring mating calls using automatic digital voice recorders at 67 sites in 12 streams and explained by 8 environmental variables: water flow volume, temperature, pH, electrical conductivity, ammonium (NH4+-N) concentration, elevation, slope, and forest stand age. The flow volume was negatively associated with occurrences in B. subaspera and O. splendida, but not O. amamiensis. Odorrana splendida occurred more frequently at higher elevations. Babina subaspera and O. splendida showed positive environmental correlations, indicating that they preferred similar environmental conditions, while exhibiting no negative relationships with each other. Our results indicated that B. subaspera and O. splendida do not avoid each other despite potential competition during the tadpole stage. Our results demonstrated that conserving preferable areas for O. splendida would also benefit B. subaspera with no negative species interactions, but not O. amamiensis. Considering species interactions in species distribution models will help us take more effective measures in the conservation of multiple species.

Research paper thumbnail of Choice of tree holes as oviposition sites by Kurixalus eiffingeri on Iriomote Island

Herpetozoa

Oviposition site choice affects survival and growth of offspring, particularly in frogs in which ... more Oviposition site choice affects survival and growth of offspring, particularly in frogs in which the offspring cannot move from the oviposition site. We intended to find the features of tree holes used for oviposition by Kurixalus eiffingeri on Iriomote Island. We measured eight tree hole variables to determine which should be included in the best model to explain breeding use by K. eiffingeri. Out of 32 tree holes examined, we found five that were used for oviposition. The best model included the height above the ground and angle of opening. Higher located tree holes and a larger opening angle were associated with more frequent oviposition by K. eiffingeri. This trend may be due to the higher predation risk in lower tree holes with a steeper opening. The importance of the height of the breeding site above ground was also noted in a previous study on bamboo stumps in Taiwan, but the opening angle was only salient in this study. Our study suggested that the same species in different ...

Research paper thumbnail of Effects of topography and anthropogenic alterations in forest environments on the breeding use by two endangered frog species in amami-oshima Island

Journal of Forest Research

Research paper thumbnail of Functions of indigenous animals in paddy fields: an in situ experiment on their effects on water quality, phytoplankton, weeds, soil structure, and rice growth

Paddy and Water Environment

Research paper thumbnail of A Comparison between Wet-only and Bulk Deposition at Two Forest Sites in Japan

Asian Journal of Atmospheric Environment

Research paper thumbnail of Species-specific growth patterns of trees neighboring dead oak trees caused by Japanese oak wilt disease

Journal of Forest Research

Research paper thumbnail of Growth of Japanese Toad (Bufo japonicus formosus) Tadpoles Fed Different Food Items

Current Herpetology

ABSTRACT Suitability of different food items for tadpoles of the Japanese toad (Bufo japonicus fo... more ABSTRACT Suitability of different food items for tadpoles of the Japanese toad (Bufo japonicus formosus) was studied by rearing experiments. Tadpoles were fed single food items (leaf litter, algae, or sludgeworms) individually in the laboratory, and their survival, growth, and development were compared. All individuals metamorphosed successfully. Litter-fed tadpoles metamorphosed at a significantly smaller size than algae- or worm-fed tadpoles, but the latter two metamorphosed at a similar size. The larval period showed little difference among the three food treatments.

Research paper thumbnail of Examination of the link between life stages uncovered the mechanisms by which habitat characteristics affect odonates

Research paper thumbnail of Post-metamorphic Costs of Carnivorous Diets in an Omnivorous Tadpole

Research paper thumbnail of Minimum Longevity and Growth of the Invasive Green Anole, Anolis carolinensis , in Chichi-jima of the Ogasawara Islands, Japan

Current Herpetology, 2016

Research paper thumbnail of Development and characterization of new microsatellite loci in the Otton frog (Babina subaspera) and cross-amplification in a congeneric species, Holst’s frog (B. holsti)

Conservation Genetics Resources, Jun 14, 2013

The Otton frog (Babina subaspera) and Holst's frog (Babina holsti) are both endangered sister spe... more The Otton frog (Babina subaspera) and Holst's frog (Babina holsti) are both endangered sister species belonging to family Ranidae. For extensive genetic and ecological research of these species, we isolated and characterized 8 new microsatellite loci of the Otton frog and validated cross-amplification in Holst's frog along with 8 previously reported loci. The total number of alleles and the expected heterozygosity of newly isolated loci in the Otton frog population ranged from 5 to 12 and from 0.620 to 0.905, respectively. We also confirmed cross-amplification in 4 of the new loci and in all previously reported loci in Holst's frog with the same level of polymorphism as the Otton frog. Our findings suggest that these novel loci will be applicable for conservation genetic studies across varying scales.

Research paper thumbnail of Are Forest Roads Attractive Hunting Sites for Frogs? A Comparison of On-Road and In-Forest Prey Biomass and Composition in Amami Island

Current Herpetology, 2016

Research paper thumbnail of Isolation and characterization of eight microsatellite loci in the Otton frog, Babina subaspera

Journal of Forest Research

The Otton frog, Babina subaspera, is an endangered forest frog species with unusual morphological... more The Otton frog, Babina subaspera, is an endangered forest frog species with unusual morphological and ecological features compared with other frogs. Eight microsatellite markers were isolated from B. subaspera and characterized with 24 individuals from Amami Islands, Kagoshima prefecture, Japan. The number of alleles observed for each locus ranged from 9 to 19 (average 13.9). The observed heterozygosity (H O) and the expected heterozygosity (H E) ranged from 0.71 to 0.92 and 0.83 to 0.92, respectively. These microsatellites will be useful for future genetic studies of B. subaspera, which will be essential in the conservation of this species.

Research paper thumbnail of Exploration of aversive bioacoustics for the effective management of invasive green anoles (Anolis carolinensis)

Journal for Nature Conservation

Research paper thumbnail of Larval food habits of the Forest Green Tree Frog

Bulletin of the Herpetological Society of Japan, 2005

Research paper thumbnail of Comparison of the detection of 3 endangered frog species by eDNA and acoustic surveys across 3 seasons

Freshwater Science, 2020

For conservation of endangered species, basic ecological information is indispensable. Environmen... more For conservation of endangered species, basic ecological information is indispensable. Environmental DNA (eDNA) is increasingly used to estimate the presence/absence of aquatic organisms such as frog species. However, the efficiency of detecting eDNA may depend on the ecological characteristics of the target frog species. Here, we adopted an eDNA approach for detecting 3 endangered Japanese species (Babina subaspera, Odorrana splendida, and O. amamiensis). We compared eDNA detection with a traditional acoustic survey method in 3 different seasons. Detection of species was not always consistent between the 2 methods, probably because acoustic surveys target only calling adult males but eDNA detects individuals of both sexes and at any life-history stage in water. Moreover, the differences in detection patterns between the 2 methods among species may be correlated with different characteristics of mating behavior (e.g., calling volume) and life history of tadpoles (e.g., migration ability). The optimal season for detection by eDNA method also differed between the 3 species, probably because of differences in breeding season and larval characteristics. We show that results obtained from eDNA detection methods and traditional field observation techniques, including acoustic surveys, are not always consistent with each other but rather depend on the ecological characteristics of the respective target species. It is therefore necessary to consider the ecological traits of frog species, such as breeding season and seasonal shifts in tadpole abundance, when applying eDNA methods for distribution surveys.

Research paper thumbnail of Shredder���tadpole facilitation of leaf litter decomposition in a tropical stream

Freshwater Biology, 2009

1. Leaf litter decomposition is one of the most important ecosystem processes in streams. Recent ... more 1. Leaf litter decomposition is one of the most important ecosystem processes in streams. Recent studies suggest that facilitation, in which litter is processed by a succession of species with differing abilities and requirements, may be important in making the nutrients bound in litter available to the stream assemblage. 2. We predicted that stream invertebrates that feed on terrestrial leaf litter (shredders) and tadpoles would facilitate leaf litter decomposition by changing the quality of leaf material directly via physical contact or indirectly via nutrient release. We experimentally examined the ability of shredders and tadpoles to break down leaves, independently and together, in artificial streams beside a natural forest stream. 3. The decomposition rate was greater when shredders and tadpoles were together than was expected from rates in single-species treatments, indicating that facilitation occurred. This facilitation operated in one direction only: the rate of leaf breakdown by tadpoles was higher when leaves had been partly processed by shredders, but there was no similar effect when leaves previously occupied by tadpoles were processed by shredders. We did not detect facilitation caused by indirect nutrient release. 4. Shredders may have benefited tadpoles by roughening leaf surfaces, making them easier for the tadpoles to consume and enhancing leaf breakdown in the presence of both taxa. This indicates that the loss of a single species can have impacts on ecosystem functioning that go beyond the loss of its direct contribution.

Research paper thumbnail of Can ecological stoichiometry help explain patterns of biological invasions?

Oikos, 2010

Skip to Main Content. ...

Research paper thumbnail of Figure 2 from: Sato TC, Iwai N (2021) Choice of tree holes as oviposition sites by Kurixalus eiffingeri on Iriomote Island. Herpetozoa 34: 201-205. https://doi.org/10.3897/herpetozoa.34.e67271

Research paper thumbnail of Figure 3 from: Sato TC, Iwai N (2021) Choice of tree holes as oviposition sites by Kurixalus eiffingeri on Iriomote Island. Herpetozoa 34: 201-205. https://doi.org/10.3897/herpetozoa.34.e67271

Research paper thumbnail of Calling-Site Preferences of Three Co-occurring Endangered Frog Species on Amami-Oshima Island

Herpetologica

Abstract Hotspots of amphibian species diversity typically occur in limited geographical ranges, ... more Abstract Hotspots of amphibian species diversity typically occur in limited geographical ranges, and critically endangered habitats often contain a large number of endemic amphibian species. In such regions, it is prudent to engage conservation strategies for multiple amphibian species simultaneously. To correctly identify suitable habitats for multiple species, species interactions should be considered in species distribution models. In this study, we adopted a joint species distribution model to determine the abiotic and biotic factors that affect calling-site choice in three endangered co-occurring frog species on Amami-Oshima Island, and examined whether they co-occur more than expected after considering the overlapping preferences in environmental variables. Occurrences of Babina subaspera, Odorrana splendida, and O. amamiensis were assessed by monitoring mating calls using automatic digital voice recorders at 67 sites in 12 streams and explained by 8 environmental variables: water flow volume, temperature, pH, electrical conductivity, ammonium (NH4+-N) concentration, elevation, slope, and forest stand age. The flow volume was negatively associated with occurrences in B. subaspera and O. splendida, but not O. amamiensis. Odorrana splendida occurred more frequently at higher elevations. Babina subaspera and O. splendida showed positive environmental correlations, indicating that they preferred similar environmental conditions, while exhibiting no negative relationships with each other. Our results indicated that B. subaspera and O. splendida do not avoid each other despite potential competition during the tadpole stage. Our results demonstrated that conserving preferable areas for O. splendida would also benefit B. subaspera with no negative species interactions, but not O. amamiensis. Considering species interactions in species distribution models will help us take more effective measures in the conservation of multiple species.

Research paper thumbnail of Choice of tree holes as oviposition sites by Kurixalus eiffingeri on Iriomote Island

Herpetozoa

Oviposition site choice affects survival and growth of offspring, particularly in frogs in which ... more Oviposition site choice affects survival and growth of offspring, particularly in frogs in which the offspring cannot move from the oviposition site. We intended to find the features of tree holes used for oviposition by Kurixalus eiffingeri on Iriomote Island. We measured eight tree hole variables to determine which should be included in the best model to explain breeding use by K. eiffingeri. Out of 32 tree holes examined, we found five that were used for oviposition. The best model included the height above the ground and angle of opening. Higher located tree holes and a larger opening angle were associated with more frequent oviposition by K. eiffingeri. This trend may be due to the higher predation risk in lower tree holes with a steeper opening. The importance of the height of the breeding site above ground was also noted in a previous study on bamboo stumps in Taiwan, but the opening angle was only salient in this study. Our study suggested that the same species in different ...

Research paper thumbnail of Effects of topography and anthropogenic alterations in forest environments on the breeding use by two endangered frog species in amami-oshima Island

Journal of Forest Research

Research paper thumbnail of Functions of indigenous animals in paddy fields: an in situ experiment on their effects on water quality, phytoplankton, weeds, soil structure, and rice growth

Paddy and Water Environment

Research paper thumbnail of A Comparison between Wet-only and Bulk Deposition at Two Forest Sites in Japan

Asian Journal of Atmospheric Environment

Research paper thumbnail of Species-specific growth patterns of trees neighboring dead oak trees caused by Japanese oak wilt disease

Journal of Forest Research

Research paper thumbnail of Growth of Japanese Toad (Bufo japonicus formosus) Tadpoles Fed Different Food Items

Current Herpetology

ABSTRACT Suitability of different food items for tadpoles of the Japanese toad (Bufo japonicus fo... more ABSTRACT Suitability of different food items for tadpoles of the Japanese toad (Bufo japonicus formosus) was studied by rearing experiments. Tadpoles were fed single food items (leaf litter, algae, or sludgeworms) individually in the laboratory, and their survival, growth, and development were compared. All individuals metamorphosed successfully. Litter-fed tadpoles metamorphosed at a significantly smaller size than algae- or worm-fed tadpoles, but the latter two metamorphosed at a similar size. The larval period showed little difference among the three food treatments.

Research paper thumbnail of Examination of the link between life stages uncovered the mechanisms by which habitat characteristics affect odonates

Research paper thumbnail of Post-metamorphic Costs of Carnivorous Diets in an Omnivorous Tadpole

Research paper thumbnail of Minimum Longevity and Growth of the Invasive Green Anole, Anolis carolinensis , in Chichi-jima of the Ogasawara Islands, Japan

Current Herpetology, 2016

Research paper thumbnail of Development and characterization of new microsatellite loci in the Otton frog (Babina subaspera) and cross-amplification in a congeneric species, Holst’s frog (B. holsti)

Conservation Genetics Resources, Jun 14, 2013

The Otton frog (Babina subaspera) and Holst's frog (Babina holsti) are both endangered sister spe... more The Otton frog (Babina subaspera) and Holst's frog (Babina holsti) are both endangered sister species belonging to family Ranidae. For extensive genetic and ecological research of these species, we isolated and characterized 8 new microsatellite loci of the Otton frog and validated cross-amplification in Holst's frog along with 8 previously reported loci. The total number of alleles and the expected heterozygosity of newly isolated loci in the Otton frog population ranged from 5 to 12 and from 0.620 to 0.905, respectively. We also confirmed cross-amplification in 4 of the new loci and in all previously reported loci in Holst's frog with the same level of polymorphism as the Otton frog. Our findings suggest that these novel loci will be applicable for conservation genetic studies across varying scales.

Research paper thumbnail of Are Forest Roads Attractive Hunting Sites for Frogs? A Comparison of On-Road and In-Forest Prey Biomass and Composition in Amami Island

Current Herpetology, 2016

Research paper thumbnail of Isolation and characterization of eight microsatellite loci in the Otton frog, Babina subaspera

Journal of Forest Research

The Otton frog, Babina subaspera, is an endangered forest frog species with unusual morphological... more The Otton frog, Babina subaspera, is an endangered forest frog species with unusual morphological and ecological features compared with other frogs. Eight microsatellite markers were isolated from B. subaspera and characterized with 24 individuals from Amami Islands, Kagoshima prefecture, Japan. The number of alleles observed for each locus ranged from 9 to 19 (average 13.9). The observed heterozygosity (H O) and the expected heterozygosity (H E) ranged from 0.71 to 0.92 and 0.83 to 0.92, respectively. These microsatellites will be useful for future genetic studies of B. subaspera, which will be essential in the conservation of this species.