Biology subjects

Terui, A.

Publications and source records attributed to Terui, A..

6 recordsLinked to original sources

bioRxiv2024

Multiple stressors in river networks: local and downstream effects on freshwater macroinvertebrates

River networks are complex ecosystems characterized by a continuous exchange of material and energy through longitudinal gradients. These ecosystems are threatened by various human-induced stressors, which frequently co-occur and may interact in complex ways, potentially triggering cascading effects in the river network. Aiming at assessing single and combined effects of flow intermittency and light pollution on macroinvertebrate communities, we performed a multiple stressors experiment in 18 flow-through mesocosms. Each mesocosm was designed to mimic a simplified river network, with two upstream tributaries merging downstream, to assess both local and cascading effects. The experiment was performed in Summer 2021 for seven weeks (26 days of colonization, 23 days of treatment), applying the stressors either separately or combined in the upstream sections, in a randomized block design. Flow intermittency was simulated as the ponded phase of the drying process, whereas light pollution was applied with LED strips (set at 10 lux) that automatically turned on at sunset and off at sunrise. Drifting macroinvertebrates were sampled weekly during the treatment phase, and benthic macroinvertebrates at the end of the treatment phase. Both stressors individually applied had negative effects on the benthos, whereas drift decreased with flow intermittency and increased with light pollution. When combined upstream, stressors showed dominant effects of flow intermittency on the benthos and interactive effects on the drift. The effects of the single stressors and their interactions propagated along the river network, with stronger downstream effects when stressors co-occurred upstream. These findings showed that the spatial distribution of multiple stressors along the river network can affect their resultant downstream effects, highlighting the importance of framing multiple stressors research in a spatial context. Considering the pressing needs of the growing human population, our results represent a step forward in anticipating cumulative stressors effects, informing efficient conservation strategies for protecting freshwater ecosystems.

ecology↗

bioRxiv2023

Food web complexity modulates environmental impacts on food chain length

Food chain length (FCL), a crucial aspect of biodiversity, has long been debated for its determinants. Previous studies proposed resource availability, disturbance, and ecosystem size as environmental drivers. However, studies using stable isotope approaches have shown inconsistent results, indicating missing links between environmental drivers and FCL. Here, we hypothesized that species richness and motifs (i.e., 3-species subgraphs) modulated environmental effects on FCL. Combining empirical food webs with our N -species food web model, we found that FCL disproportionately changed at low species richness with saturation at high species richness. This functional response was essential to the interdependent effects of disturbance and ecosystem size in our model. Disturbance more strongly regulated FCL in smaller ecosystems, where species richness was low. Similarly, increasing ecosystem size enhanced FCL under strong, but not weak, disturbance regimes. Our study suggests that internal food web structure should deepen our understanding of how FCL changes over environments.

ecology↗

bioRxiv2022

Mathematical characterization of fractal river networks

Carraro and Altermatt1 performed an extensive analysis to study scaling properties of river networks. They concluded that: (1) branching "probability" is better termed as branching "ratio" for real river networks because it is not a probability; (2) branching ratio is a scale-dependent quantity as the value changes across spatial resolutions at which river networks are extracted (expressed as the threshold catchment area AT that initiates channels or pixel size l); (3) Optimal Channel Networks most accurately predicted the metapopulation stability and capacity. However, the supporting ground for these conclusions is either seriously flawed or inconclusive due to the improper use of branching probability, scale invariance, dimensions, and units.

ecology↗

bioRxiv2022

Intentional stocking undermines ecological stability

The past decades have witnessed efforts to unveil ecological risks associated with massive releases of captive-bred individuals ("stock enhancement"). Still, we may underestimate the negative impact because current schemes rarely consider the consequences of stock enhancement for the whole ecological community. Here, we use theory and long-term data of Japanese stream fish communities to show that stock enhancement undermines community stability. Our theory predicted that stock enhancement destabilizes community dynamics by facilitating competitive exclusion. Consistent with this prediction, fish communities showed greater temporal fluctuations and fewer species richness in rivers with the intensive stocking of hatchery masu salmon - a major freshwater resource in the region. Our findings paint a bleak picture for stock enhancement, reinforcing the recurrent calls for alternative management strategies. One Sentence SummaryLarge-scale releases of captive-bred organisms undermine the long-term persistence of ecological communities by disrupting the stable coexistence of competing species.

ecology↗

bioRxiv2021

Ecosystem size and complexity dictate riverine biodiversity

Larger ecosystems support more species; this ubiquitous pattern is the foundation of current conservation schemes. However, many ecosystems possess a complex spatial structure that cannot be represented by area, and the role of such complexity in scaling biodiversity is largely unknown. Here, we use theory and extensive fish community data from two distinct geographic regions (Japan and United States) to show that ecosystem size and complexity dictate riverine biodiversity. We found that larger and more branched complex river networks harbored greater species richness due to increased space and environmental heterogeneity. The complexity effect was comparable to the size effect, and this pattern has emerged regardless of ecological contexts. The dual control of biodiversity may be a pervasive feature that has far-reaching implications for biodiversity conservation. One sentence summaryThis study provides the first evidence that ecosystem size and complexity play comparable roles in regulating biodiversity.

ecology↗

bioRxiv2019

A Bayesian approach to inferring dispersal kernels with incomplete mark-recapture data

Dispersal is a fundamental ecological process that links populations, communities and food webs in space. However, dispersal is tremendously difficult to study in the wild because we must track individuals dispersing in a landscape. One conventional method to measure animal dispersal is a mark-recapture technique. Despite its usefulness, this approach has been recurrently criticized because it is virtually impossible to survey all possible ranges of dispersal in nature. Here, I propose a novel Bayesian model to better estimate dispersal parameters from incomplete mark-recapture data. The dispersal-observation coupled model, DOCM, can extract information from both recaptured and unrecaptured individuals, providing less biased estimates of dispersal parameters. Simulations demonstrated the usefulness of DOCM under various sampling designs. I also suggest extensions of the DOCM to accommodate more realistic scenarios. Application of the DOCM may, therefore, provide valuable insights into how individuals disperse in the wild.

ecology↗