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Biology subjects

Kasada, M.

Publications and source records attributed to Kasada, M..

6 recordsLinked to original sources
bioRxiv2025

Feasibility of an eDNA-based educational program for high school students

O_LIEnvironmental education plays a crucial role in raising public awareness of ecosystem conservation. Environmental DNA (eDNA) analysis is a promising environmental education tool because it enables easy and comprehensive biodiversity assessment through simple water sampling. Despite several citizen-based surveys using eDNA analysis, minimal attention has been paid to its educational effectiveness. C_LIO_LIIn this study, we examined the educational feasibility of eDNA analysis by conducting an environmental education program that incorporated eDNA-based local fish surveys in three high schools in Japan. Through detailed questionnaire surveys conducted before and after the program, we verified whether our program increased student interest in biodiversity and ecosystem services. C_LIO_LIIn the program, students proactively identified diverse fish species living in the survey area by simply collecting water. The questionnaire survey results showed that student knowledge of and interest in biodiversity and ecosystem services increased after the program. Students became aware of local fish diversity and expressed their motivation to engage in conservation activities. We confirmed the educational impact of the program not only at the end but also immediately following the water sampling experience. C_LIO_LISynthesis and applications. These results provide the first empirical evidence of the positive effects of eDNA analysis on student environmental awareness and engagement. Our program provides a feasible model for eDNA-based environmental education. Because eDNA analysis can be applied to diverse target taxa that are unique to a given area, similar environmental education programs can be conducted for various citizen groups worldwide. Our research also suggested that eDNA-based environmental education was effective for younger generations with varying levels of interest and experience in nature, showing significant potential for addressing the extinction of natural experiences and motivating citizens to participate in ecosystem conservation activities. C_LI

scientific communication and education↗
bioRxiv2023

Synergistic effects of predation and parasitism on competition between edible and inedible phytoplankton

Fungi can affect aquatic ecosystems through syntrophic and parasitic interactions with other organisms and organic matter. In pelagic systems, fungal parasites on phytoplankton can control trophic interactions and food-web dynamics, e.g., zooplankton grazing on fungal parasite zoospores creates an alternative energy pathway (termed "mycoloop") from otherwise inedible phytoplankton species. We aim to investigate how the mycoloop influences community dynamics in aquatic food-webs combining experimental and modelling approaches. We assembled an experimental system consisting of an inedible (host) phytoplankton species and its parasitic chytrid, an edible (non-host) phytoplankton species, and a zooplankton grazer. Chytrids parasitizing increased edible phytoplankton abundance, while zooplankton grazing decreased edible phytoplankton abundance. In the presence of zooplankton and chytrids, competition effects between edible and inedible phytoplankton species depended on nutrient levels. At high nutrient levels, competition was balanced by an indirect positive chytrid effect and negative zooplankton grazing effects on edible phytoplankton. In contrast, at low nutrient levels, we found chytrid had a negative impact on edible phytoplankton synergistically with zooplankton. Mathematical investigations suggest that the synergistic effect can be caused by the mycoloop. This indicates that the mycoloop substantially affects predator-prey interactions and phytoplankton competition with yet unknown ecological consequences.

ecology↗
bioRxiv2022

From microbes to mammals: pond biodiversity homogenization across different land-use types in an agricultural landscape

Local biodiversity patterns are expected to strongly reflect variation in topography, land use, dispersal boundaries, nutrient supplies, contaminant spread, management practices and other anthropogenic influences. In contrast, studies focusing on specific taxa revealed a biodiversity homogenization effect in areas subjected to long-term intensive industrial agriculture. We investigated whether land use affects biodiversity and metacommunity structure in 67 kettle holes (KH) representing small aquatic islands embedded in the patchwork matrix of a largely agricultural landscape comprising grassland, forest, and arable fields. These KH, similar to millions of standing water bodies of glacial origin, spread across northern Europe, Asia, and North America, are physico-chemically diverse, differ in the degree of coupling with their surroundings. We assessed biodiversity patterns of eukaryotes, Bacteria and Archaea in relation to environmental features of the KH, using deep-amplicon-sequencing of eDNA. First, we asked whether deep sequencing of eDNA provides a representative picture of KH biodiversity across the three domains of life. Second, we investigated if and to what extent KH biodiversity is influenced by the surrounding land-use. Our data shows that deep eDNA amplicon sequencing is useful for in-depth assessments of cross-domain biodiversity comprising both micro- and macro-organisms, but, has limitations with respect to single-taxa conservation studies. Using this broad method, we show that sediment eDNA, integrating several years to decades, depicts the history of agricultural land-use intensification. The latter, coupled with landscape wide nutrient enrichment (including by atmospheric deposition), groundwater connectivity between KH and organismal movement in the tight network of ponds, resulted in a biodiversity homogenization in the KH water, levelling off todays detectable differences in KH biodiversity between land-use types.

ecology↗
bioRxiv2021

Hierarchical trait-based model reveals positive and negative effects of land abandonment on butterfly communities across climatic regions in Japan

Land abandonment may decrease biodiversity but also provides an opportunity for rewilding. It is therefore necessary to identify areas that may benefit from traditional land management practices and those that may benefit from a lack of human intervention. In this study, we conducted comparative field surveys of butterfly occurrence in abandoned and inhabited settlements in 18 regions of diverse climatic zones in Japan to test the hypotheses that species-specific responses to land abandonment correlate with climatic niches and habitat preferences. Hierarchical models that unified species occurrence and habitat preferences revealed that negative responses to land abandonment were associated with species that have cold climatic niches and utilize open habitats, suggesting that species negatively impacted by land abandonment will decline more due to future climate warming. Maps representing species gains and losses due to land abandonment, which were created from the model estimates, showed similar geographic patterns, but some areas exhibited high species losses relative to gains. Our hierarchical modelling approach was useful for scaling up local-scale effects of land abandonment to a macro-scale assessment, which is crucial to developing spatial conservation strategies in the era of depopulation.

ecology↗
bioRxiv2020

Optimal Random Avoidance Strategy in Prey-Predator Interactions

It has recently been reported that individual animals, ranging from insects to birds and mammals, exhibit a special class of random walks, known as Levy walks, which can lead to higher search efficiency than normal random walks. However, the role of randomness or unpredictability in animal movements is not very well understood. In the present study, we used a theoretical framework to explore the advantage of Levy walks in terms of avoidance behaviour in prey-predator interactions and analysed the conditions for maximising the preys survival rate. We showed that there is a trade-off relationship between the predictability of the preys movement and the length of time of exposure to predation risk, suggesting that it is difficult for prey to decrease both parameters in order to survive. Then, we demonstrated that the optimal degree of randomness in avoidance behaviour could change depending on the predators ability. In particular, Levy walks resulted in higher survival rates than normal random walks and straight movements when the physical ability of the predators was high. This indicates that the advantage of Levy walks may also be present in random avoidance behaviour and provides new insights into why Levy walks can evolve in terms of randomness.

animal behavior and cognition↗