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The signal crayfish, Pacifastacus leniusculus , is non-native to Japan, and its invasion may have contributed to the habitat loss of the endemic Japanese crayfish, Cambaroides japonicus. We assessed the distribution of the signal crayfish and the Japanese crayfish in small streams that flow into Lake Akan (Hokkaido, Japan), which the signal crayfish inhabits. We conducted this survey with 2 methods: analysis of environmental DNA (eDNA) and hand capture. Of the 17 streams we surveyed, we detected signal crayfish DNA in 16 streams and Japanese crayfish DNA in 9 streams. In contrast, with our hand-capture survey of the same 17 streams, we found signal crayfish in 9 streams and Japanese crayfish in 4 streams. These results suggest that the signal crayfish may have invaded almost all the small streams with culverts around Lake Akan. The presence of signal crayfish was also confirmed on the upstream side of a 69-cm-high road-crossing culvert. There were only 2 culverts above which the absence of signal crayfish was supported by eDNA analysis, suggesting that culverts have limited effectiveness against signal crayfish invasion in our study site. Active species-specific removal projects may be an effective management option to minimize the negative impacts of signal crayfish where they are already present. eDNA has great potential as a cost-effective tool to monitor crayfish range expansion. [ABSTRACT FROM AUTHOR]

Abstract: Chaotic breathers of two types are generated in two-dimensional Morse lattices with on-site harmonic potentials. In both a triangular and a square configuration, initial highest-frequency (-mode) disturbances evolve into chaotic breathers. Depending on the magnitude of the parameters in the Morse potential, either quasi-one-dimensional localized chaotic breathers or two-dimensional localized (bell-shaped) ones are numerically observed when the on-site harmonic potential becomes significant. Both types of chaotic breather move irregularly within the lattice, and finally decay out into a thermalization state after a fairly long time. Quasi-one-dimensional localized chaotic breathers are favored as the strength of nonlinearity increases and they decay faster than two-dimensional localized ones. [Copyright &y& Elsevier]

Although environmental DNA (eDNA) metabarcoding is an exceptionally useful and powerful tool for monitoring biodiversity, little is known about whether the traits of organisms and their ecosystem characteristics affect eDNA metabarcoding performance. Nationwide surveys can provide more detailed insights, yet such studies have rarely been conducted.In order to evaluate eDNA metabarcoding performance in broad‐scale monitoring, we examined the effects of species ecological/biological traits and ecosystem characteristics on species detection rates and the implications for community analysis. In addition, we tested the effects of sample mixing and transportation methods, including cooling and freezing, on eDNA metabarcoding. On a nationwide scale, we conducted eDNA metabarcoding for fish communities in 18 Japanese lakes.By comparing species records, we observed that certain traits, including body size, body shape, saltwater tolerance and habitat preference, influenced eDNA detection. In addition, the proportion of species detected decreased significantly with an increase in lake surface area owing to ecosystem size effect on species detection.We conclude that species traits, including habitat preference, body size and ecosystem size, should be considered when assessing the eDNA metabarcoding performance in broad‐scale monitoring. [ABSTRACT FROM AUTHOR]

Molecular methods, including those for environmental DNA (eDNA), provide essential information for biological and conservation sciences. Molecular measurements are often performed in the laboratory, which limits their scope, especially for rapid on‐site analysis. eDNA methods for species detection provide essential information for the management and conservation of species and communities in various environments. We have developed an innovative novel method for on‐site eDNA measurements using an ultrarapid mobile PCR platform. We tested the ability of our method to detect the distribution of silver carp, Hypophthalmichthys molitrix, in rivers and lakes. Our method reduced the measurement time to 30 min and provided high detectability of aquatic organisms compared to national observation surveys that use multiple fishing nets and laboratory extraction/detection using a benchtop qPCR platform. Our on‐site eDNA method can be immediately applied to various taxa and environments. [ABSTRACT FROM AUTHOR]

In recent years, biodiversity loss has become one of the most serious environmental issues worldwide, especially in aquatic ecosystems. To avoid diversity loss, it is necessary to monitor biological communities, and environmental DNA (eDNA) metabarcoding has been developed as a rapid, noninvasive, and cost-effective method for aquatic biodiversity monitoring. Although this method has been applied to various environments and taxa, a detailed assessment of the efficient sampling methods for monitoring is still required. In this study, we explored eDNA metabarcoding sampling methods for fish at a single site to maximize the number of detected species using realistic effort in a natural, small river. We considered the following three parameters: sample type (water or sediment), sample position at a site (right and left shore and center of the river), and water volume (10–4000 mL). The results suggested that the number of detected species from sedimentary eDNA was equivalent to that from aqueous eDNA, although the species composition was different. The number of detected species could be saturated by collecting a 1000 mL water sample, regardless of sampling position within a survey site. However, sedimentary eDNA showed a spatially heterogeneous species composition between sampling positions within a survey site despite the short distance (5 m) between positions, without apparent differences in physical properties such as velocity and sediment particle distribution. By completing eDNA biodiversity monitoring of fish with 1000 mL water samples across the whole river, we detected more fish species than in previous traditional surveys conducted at the same sites. Thus, the aqueous eDNA metabarcoding method is as efficient as traditional surveys, while sedimentary eDNA metabarcoding could complement the results of aqueous eDNA metabarcoding. [ABSTRACT FROM AUTHOR]

Aim: As climate change presents a major threat to biodiversity in the next decades, it is critical to assess its impact on species habitat suitability to inform biodiversity conservation. Species distribution models (SDMs) are a widely used tool to assess climate change impacts on species' geographical distributions. As the name of these models suggests, the species level is the most commonly used taxonomic unit in SDMs. However, recently it has been demonstrated that SDMs considering taxonomic resolution below (or above) the species level can make more reliable predictions of biodiversity change when different populations exhibit local adaptation. Here, we tested this idea using the Japanese crayfish (Cambaroides japonicus), a threatened species encompassing two geographically structured and phylogenetically distinct genetic lineages. Location: Northern Japan. Methods: We first estimated niche differentiation between the two lineages of C. japonicus using n‐dimensional hypervolumes and then made climate change predictions of habitat suitability using SDMs constructed at two phylogenetic levels: species and intraspecific lineage. Results: Our results showed only intermediate niche overlap, demonstrating measurable niche differences between the two lineages. The species‐level SDM made future predictions that predicted much broader and severe impacts of climate change. However, the lineage‐level SDMs led to reduced climate change impacts overall and also suggested that the eastern lineage may be more resilient to climate change than the western one. Main conclusions: The two lineages of C. japonicus occupy different niche spaces. Compared with lineage‐level models, species‐level models can overestimate climate change impacts. These results not only have important implications for designing future conservation strategies for this threatened species, but also highlight the need for incorporating genetic information into SDMs to obtain realistic predictions of biodiversity change. [ABSTRACT FROM AUTHOR]

Summary [ABSTRACT FROM AUTHOR]

GLO:EU3/01apr21:ddi13263-toc-0001.jpg PHOTO (COLOR): . gl The photo (taken in 2009) shows an eastern lineage Japanese crayfi sh (Cambaroides japonicus) in a small woodland stream in Hokkaido, Japan. The cover image relates to the Research Article https://doi.org/10.1111/ddi.13225 "Lineage-level distribution models lead to more realistic climate change predictions for a threatened crayfi sh" by Zhixin Zhang et al. [Extracted from the article]