Nisikawa Usio

Decoupled conservatism of Grinnellian and Eltonian niches in an invasive arthropod

Whether a species niche is conserved or shifts across space and time is a question of heightened interest in ecology and evolution. Considerable scientific inquiry into this topic has used invasive species to evaluate conservatism of the Grinnellian climatic niche while generally neglecting the Eltonian functional niche. By contrast, we report here on the first simultaneous reciprocal comparison of both the Grinnellian and Eltonian niches for the globally invasive signal crayfish Pacifastacus leniusculus between its native (Pacific Northwest of North America) and non-native ranges (Japan). Using multivariate statistics and the Maxent machine-learning algorithm, we found strong evidence for a climatic niche shift between geographic regions for P. leniusculus. Pacifastacus leniusculus shifted from warmer temperatures with strong precipitation seasonality in western North America to cooler temperatures with less precipitation seasonality in Japan. However, analysis of stable isotopes of carbon and nitrogen r...

Loss of Genetic Diversity Means Loss of Geological Information: The Endangered Japanese Crayfish Exhibits Remarkable Historical Footprints

Intra-specific genetic diversity is important not only because it influences population persistence and evolutionary potential, but also because it contains past geological, climatic and environmental information. In this paper, we show unusually clear genetic structure of the endangered Japanese crayfish that, as a sedentary species, provides many insights into lesser-known past environments in northern Japan. Over the native range, most populations consisted of unique 16S mtDNA haplotypes, resulting in significant genetic divergence (overall F ST = 0.96). Owing to the simple and clear structure, a new graphic approach unraveled a detailed evolutionary history; regional crayfish populations were comprised of two distinct lineages that had experienced contrasting demographic processes (i.e. rapid expansion vs. slow stepwise range expansion) following differential drainage topologies and past climate events. Nuclear DNA sequences also showed deep separation between the lineages. Current ocean barriers to dispersal did not significantly affect the genetic structure of the freshwater crayfish, indicating the formation of relatively recent land bridges. This study provides one of the best examples of how phylogeographic analysis can unravel a detailed evolutionary history of a species and how this history contributes to the understanding of the past environment in the region. Ongoing local extinctions of the crayfish lead not only to loss of biodiversity but also to the loss of a significant information regarding past geological and climatic events.

Effects of pond draining on biodiversity and water quality of farm ponds.

Farm ponds have high conservation value because they contribute significantly to regional biodiversity and ecosystem services. In Japan pond draining is a traditional management method that is widely believed to improve water quality and eradicate invasive fish. In addition, fishing by means of pond draining has significant cultural value for local people, serving as a social event. However, there is a widespread belief that pond draining reduces freshwater biodiversity through the extirpation of aquatic animals, but scientific evaluation of the effectiveness of pond draining is lacking. We conducted a large-scale field study to evaluate the effects of pond draining on invasive animal control, water quality, and aquatic biodiversity relative to different pond-management practices, pond physicochemistry, and surrounding land use. The results of boosted regression-tree models and analyses of similarity showed that pond draining had little effect on invasive fish control, water quality, or aquatic biodiversity. Draining even facilitated the colonization of farm ponds by invasive red swamp crayfish (Procambarus clarkii), which in turn may have detrimental effects on the biodiversity and water quality of farm ponds. Our results highlight the need for reconsidering current pond management and developing management plans with respect to multifunctionality of such ponds. Efectos del Drenado de Estanques sobre la Biodiversidad y la Calidad del Agua en Estanques de Cultivo.

Shoreline urbanization interrupts allochthonous subsidies to a benthic consumer over a gradient of lake size

The role of resource subsidies across ecosystem boundaries has emerged as an important concept in contemporary ecology. For lake ecosystems, this has led to interest in quantifying the contribution of terrestrial allochthonous carbon to aquatic secondary production. An inverse relationship between habitat area and the role of allochthonous subsidies has been documented on marine islands and assumed for lakes, yet there have been no tests of this pattern among benthic (lake bottom) consumers. Here, we used carbon stable isotopes to trace terrestrial allochthonous and benthic autochthonous carbon use by the crayfish Pacifastacus leniusculus over a gradient of lake area, productivity and urbanization. Consistent with findings from terrestrial islands, habitat size dictated the importance of allochthonous subsidies, as P. leniusculus transitioned from using predominantly terrestrial carbon in small lakes to an increased reliance on autochthonous production in larger lakes. However, shoreline urbanization interacted with this pattern, particularly for small lakes where greater urbanization resulted in reduced use of allochthonous resources. As such, we provide, to our knowledge, the first confirmation of the predicted relationship between habitat size and importance of allochthonous subsidies to lake benthic consumers, but found that urbanization can interfere with this pattern.

Social-Ecological Restoration in Paddy-Dominated Landscapes

After World War II, it was the Japanese government’s official policy that farmers should own the land they cultivated. This policy was in effect until 2009, when the Agricultural Land Law was changed drastically. This change was the result of long-term serious discussions regarding which type of agricultural land user was best suited to farming. The discussion was influenced by the problem of abandoned agricultural land, which had become serious around 1990. New policy frameworks were created to prevent abandonment after 2000, and they have been T. Hashiguchi (*) School of Agriculture, Meiji University, Kawasaki 214-0033, Japan e-mail: hashiguchi.takuya@nifty.com

Effectiveness of Wildlife-Friendly Farming on Aquatic Macroinvertebrate Diversity on Sado Island in Japan

Paddy fields are important as alternative wetland habitats for a range of aquatic and semi-aquatic wildlife that once inhabited floodplain habitats. However, depopulation and aging in rural communities have led to the loss of biodiversity across rural areas of Japan. In Japan, wildlife-friendly farming is typically implemented using charismatic wildlife as an icon, and much attention has been given as a means for restoring paddy field biodiversity. Sado Island in central Japan is among the leading areas for such wildlife-friendly farming in terms of the implemented area. Nevertheless, scientific evaluation is largely lacking for the effectiveness of wildlife-friendly farming on paddy field biodiversity. Using four aquatic macroinvertebrate taxa as indicator groups, we surveyed over 300 paddy fields in winter and summer across Sado Island. In winter, although most indicator groups were significantly associated with the percentage of water coverage in paddy fields, winter flooding had limited effects on aquatic macroinvertebrate abundance or richness, because of large variations in water coverage among paddy fields. In contrast, implementing diversion ditches provided additional habitats for aquatic macroinvertebrates that prefer deep-water habitats, resulting in the separation of macroinvertebrate composition between paddy fields and their adjacent ditches in both winter and summer. Furthermore, agrochemical reduction and fallow flooding were effective in enhancing aquatic macroinvertebrate abundance and richness in summer. Overall, diverse practices of wildlife-friendly farming contributed to the enhancement of aquatic macroinvertebrate diversity on Sado Island.

Phylogeographic insights into the invasion history and secondary spread of the signal crayfish in Japan.

Abstract Successful invasion by nonindigenous species is often attributed to high propagule pressure, yet some foreign species become widespread despite showing reduced genetic variation due to founder effects. The signal crayfish (Pacifastacus leniusculus) is one such example, where rapid spread across Japan in recent decades is believed to be the result of only three founding populations. To infer the history and explore the success of this remarkable crayfish invasion, we combined detailed phylogeographical and morphological analyses conducted in both the introduced and native ranges. We sequenced 16S mitochondrial DNA of signal crayfish from across the introduced range in Japan (537 samples, 20 sites) and the native range in western North America (700 samples, 50 sites). Because chela size is often related to aggressive behavior in crayfish, and hence, their invasion success, we also measured chela size of a subset of specimens in both introduced and native ranges. Genetic diversity of introduced signal crayfish populations was as high as that of the dominant phylogeographic group in the native range, suggesting high propagule pressure during invasion. More recently established crayfish populations in Japan that originated through secondary spread from one of the founding populations exhibit reduced genetic diversity relative to older populations, probably as a result of founder effects. However, these newer populations also show larger chela size, consistent with expectations of rapid adaptations or phenotypic responses during the invasion process. Introduced signal crayfish populations in Japan originate from multiple source populations from a wide geographic range in the native range of western North America. A combination of high genetic diversity, especially for older populations in the invasive range, and rapid adaptation to colonization, manifested as larger chela in recent invasions, likely contribute to invasion success of signal crayfish in Japan.

Environmentally Friendly Farming in Japan: Introduction

Rice paddy fields are a typical component of the Satoyama (human-dominated) landscape in Japan, and they have multiple functions beyond their role in rice production. However, agricultural intensification and farmland abandonment have led to the degradation of rice paddy fields in Japan. To conserve or restore the multiple functions of paddy fields, much attention has focused on environmentally friendly farming practices. As a guide to Part 2, this chapter summarizes representative environmentally friendly farming practices in Japan.

Assessing the Difficulty of Implementing Wildlife-Friendly Farming Practices by Using the Best–Worst Scaling Approach

On Sado Island in central Japan, wildlife-friendly farming is widely practiced, using the crested ibis (Nipponia nippon) as an icon. On the basis of farmer preferences, we applied the best–worst scaling (BWS) approach to evaluate the difficulty of implementing seven representative wildlife-friendly farming practices on Sado Island. Typical wildlife-friendly farming practices include reduced inputs of agrochemicals (50 % or 80 % agrochemical reduction), organic (agrochemical-free) cultivation, winter flooding, installation of diversion ditches, installation of fishways, and installation of biotopes (fallow flooding). We conducted a questionnaire survey of 5,010 farmers on Sado Island who distributed rice to Japan Agricultural Cooperatives (JA) at the time of the survey. We employed two approaches to analyze the BWS data: counting analysis and econometric analysis. The results of both analyses showed that organic cultivation was the most difficult of all types of farming practices and that 50 % agrochemical reduction was the least difficult. As expected, the burden of implementing the various farming practices differed. When a farming practice can produce a certain amount of biodiversity with less burden, the practice is considered more efficient. The results of our analysis can be utilized to evaluate each farming practice by quantifying its cost-effectiveness. Our study approach may be an effective assessment tool for disseminating wildlife-friendly farming practices.

Assemblage Characteristics and Habitat Specificity of Carabid Beetles in a Japanese Alpine-Subalpine Zone

In lowland areas of the world and high-altitude European mountains, the species compositions, body sizes, and wing forms of carabid beetles are known to change according to vegetation structures. However, little is known regarding the assemblage structure and habitat associations of carabid beetles in Japanese alpine-subalpine areas. We surveyed carabid beetles in four habitats (snow beds, alpine meadows, Pinus scrub, and fell-fields) in the alpine-subalpine zone on Mt. Hakusan, Japan. We surveyed carabid beetles six times between mid-July and late September. Nonmetric multidimensional scaling (NMDS) and analysis of similarities (ANOSIM) revealed three distinct carabid beetle assemblages in snow beds and alpine meadows, Pinus scrub, and fell-fields. The carabid beetle assemblages in the four habitats consisted predominantly of small and/or wingless species with differential spatiotemporal variability in abundance. Biota-environment (BIO-ENV) analyses showed that the percentage coverage by Pinus scrub, soil water content, and ground surface temperature were among the most significant variables affecting carabid beetle compositions. Given their small sizes and reduced wings, which are characteristic traits for limited mobility, and high-level habitat specificity, carabid beetles in the alpine-subalpine zone may serve as an important target group to monitor the impacts of global environmental change on mountain ecosystems.