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Mori T.,Japan Aqua Restoration Research Center | Saitoh T.,Hokkaido University
Ecology | Year: 2014

The effects of both abiotic factors and biotic interactions among guilds (i.e., inter-guild effects) have been suggested to be important for understanding spatial variation in species diversity; however, compared to the abiotic effects, the processes by which the interguild effects are mediated have been little described. Hence, we investigated stream invertebrate assemblages on Hokkaido Island, Japan, and assessed how the processes of determining regional patterns in species diversity differed among guilds (collector-filterers, collectorgatherers/ shredders, scrapers, and predators) by taking both inter-guild and abiotic effects into consideration using Bayesian networks. Collector-gatherers/shredders, collector-filterers, and predators exhibited significant regional gradients in taxonomic richness. Gradients in the former two guilds can be generated by variation in flood disturbance regardless of interactions with other guilds. The gradient in predator taxonomic richness was indirectly related to the disturbance and was directly generated by bottom-up effects through their prey (collectorgatherers/ shredders and collector-filterers). We found that not only environmental factors, but also inter-guild effects may be essential for forming the regional gradient in predators, unlike those for collector-gatherers/shredders and collector-filterers. The processes underlying the regional variation in taxonomic richness of the three guilds are interpreted in terms of the "more individuals" hypothesis, facilitation, and predator-prey relationships. © 2014 by the Ecological Society of America. Source

Kume M.,Hokkaido University | Kume M.,Japan Aqua Restoration Research Center
Zoological Studies | Year: 2011

Clutch and egg sizes of two migratory forms of the threespine stickleback Gasterosteus aculeatus in eastern Hokkaido, Japan. Zoological Studies 50(3): 309-314. Clutch and egg sizes were compared between the Japan Sea and Pacific Ocean forms of the threespine stickleback collected from the Bekanbeushi River in eastern Hokkaido, Japan. The Japan Sea form produced many small-sized eggs, whereas the Pacific Ocean form produced fewer large-sized eggs, suggesting the existence of a trade-off between clutch and egg sizes in both forms. A previous study revealed that the 2 forms diverged in their breeding habitats by using different salinity regimes within a single watershed. These findings suggest that the Japan Sea and Pacific Ocean forms have evolved different reproductive strategies and characteristics in response to differing salinities and properties of their respective environments. Source

Doi H.,Ehime University | Doi H.,Carl von Ossietzky University | Takahashiz M.,Hokkaido University | katano I.,Carl von Ossietzky University | katano I.,Japan Aqua Restoration Research Center
Global Change Biology | Year: 2010

Climate change is inducing changes in the phenological timings of organisms. Genetic diversity could influence phenological responses to climate change, but empirical evidence is very limited. We estimated the regional variation across Japan in flowering and leaf budburst dates of plants based on a dataset of phenological timings from 1953 to 2005. The observed plants' genetic diversities varied according to human cultivation. The within-species variations of phenological response to temperature as well as regional variations were less in the plant populations with lower genetic diversity. Thus, genetic diversity influences the variation in phenological responses of plant populations. Under increased temperatures, low variation in phenological responses may allow drastic changes in the phenology of plant populations with synchronized phenological timings. Our findings indicate that we should pay attention to maintaining genetic diversity of populations to alleviate changes in phenology due to future climate change. © 2009 Blackwell Publishing Ltd. Source

Nagayama S.,Japan Civil Engineering Research Institute for Cold Region | Nagayama S.,Japan Aqua Restoration Research Center | Nakamura F.,Hokkaido University
Landscape and Ecological Engineering | Year: 2010

To provide river managers and researchers with practical knowledge about fish rehabilitation, various studies of fish habitat rehabilitation that used wood were reviewed. The review focuses on fish responses, wood installation methods, and geomorphic features of the rehabilitation sites. Most studies were conducted in moderately sized (small and medium) streams with relatively high bed gradients and aimed to improve the habitats of salmonid species. In this stream type, structures spanning the full (log dam) and partial (log deflector) width of the river were most common, and wood structures that created pools and covers were successful in improving fish habitat. Some projects were conducted in moderately sized low-gradient streams, in which wooden devices used to create instream cover were effective for fish assemblages. There were few studies in other aquatic ecosystems. However, well-designed large wood structures, known as engineered log jams, were used in rehabilitation projects for large rivers. In slack-water or lentic systems such as side-channels, estuaries, and reservoirs, small and large wood structures that created cover were used to improve habitat for many fish species. For successful fish habitat rehabilitation projects, the hydrogeomorphic conditions of rehabilitation sites should be carefully examined to avoid physical failure of wood structures. Although artificial wood structures can be used to improve fish habitat in various aquatic ecosystems, they should be considered to be a complementary or interim habitat enhancement technique. The recovery of natural dynamic processes at the watershed scale is the ultimate target of restoration programs. © 2009 International Consortium of Landscape and Ecological Engineering and Springer. Source

Negishi J.N.,Japan Aqua Restoration Research Center | Negishi J.N.,Hokkaido University | Sagawa S.,Japan Aqua Restoration Research Center | Kayaba Y.,Japan Aqua Restoration Research Center | And 3 more authors.
Freshwater Biology | Year: 2012

Understanding mechanisms behind the distribution of organisms along a gradient of hydrological connectivity is crucial for sustainable management of river-floodplain systems. We tested the hypothesis that frequency of flood pulses exerts a direct influence on the distribution of freshwater mussels (Unionoida) by creating a local environment that limits their fitness. Multiscale habitat analyses combined with transplant-rearing experiments were carried out with a focus on abundance, presence/absence, survival rates and growth rates of mussels. Sixty-nine floodplain waterbodies (FWBs) were surveyed within a 15-km lowland segment of the Kiso River in Japan. The abundance of mussels significantly increased with increased frequency of inundation associated with flood pulses at the among-FWB scale, while the probability of occurrence of mussels was negatively predicted by the amount of benthic organic matter at the within-FWB scale. Field-rearing experiments showed that survival rates were low and growth rates nearly zero in infrequently inundated FWBs (these FWBs had no naturally occurring resident mussels). In such FWBs, hypoxia (DO<2mgL -1) was frequently observed near the bottom when temperature was optimal for mussel growth (>15°C). These findings demonstrated that flood pulse frequency was the most important factor in determining mussel distribution in FWBs because it directly limits mussels' fitness by mediating local environmental factors, possibly dissolved oxygen (DO) levels. Successful restoration efforts for mussel habitat conservation should focus on processes that lead to improved local conditions. © 2012 Blackwell Publishing Ltd. Source

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