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The process of phenotypic adaptation to the environments is widely recognized. However, comprehensive studies integrating phylogenetic, phenotypic, and ecological approaches to assess this process are scarce. Our study aims to assess whether local adaptation may explain intraspecific differentiation by quantifying multidimensional differences among populations in closely related lucanid species, Platycerus delicatulus and Platycerus kawadai, which are endemic saproxylic beetles in Japan. First, we determined intraspecific analysis units based on nuclear and mitochondrial gene analyses of Platycerus delicatulus and Platycerus kawadai under sympatric and allopatric conditions. Then, we compared differences in morphology and environmental niche between populations (analysis units) within species. We examined the relationship between morphology and environmental niche via geographic distance. P. kawadai was subdivided into the "No introgression" and "Introgression" populations based on mitochondrial COI gene – nuclear ITS region discordance. P. delicatulus was subdivided into "Allopatric" and "Sympatric" populations. Body length differed significantly among the populations of each species. For P. delicatulus, character displacement was suggested. For P. kawadai, the morphological difference was likely caused by geographic distance or genetic divergence rather than environmental differences. The finding showed that the observed mitochondrial–nuclear discordance is likely due to historical mitochondrial introgression following a range of expansion. Our results show that morphological variation among populations of P. delicatulus and P. kawadai reflects an ecological adaptation process based on interspecific interactions, geographic distance, or genetic divergence. Our results will deepen understanding of ecological specialization processes across the distribution and adaptation of species in natural systems. [ABSTRACT FROM AUTHOR]

The genus Platycerus (Coleoptera: Lucanidae) is a small stag beetle group, which is adapted to cool-temperate deciduous broad-leaved forests in East Asia. Ten Platycerus species in Japan form a monophyletic clade endemic to Japan and inhabit species-specific climatic zones. They are reported to have co-evolutionary associations with their yeast symbionts of the genus Sheffersomyces based on host cytochrome oxidase subunit I (COI) and yeast intergenic spacer (IGS) phylogenies. Here we examined the heat tolerances of the yeast colonies isolated from the mycangia of 37 females belonging ten Japanese Platycerus species. The upper limits of growth and survival temperatures of each colony were decided by cultivating it at ten temperature levels between 17.5 and 40°C. Although both temperatures varied during 25.0–31.25°C, the maximum survival temperatures (MSTs) were a little higher than the maximum growth temperatures (MGTs) in 16 colonies. Pearson's correlations between these temperatures and environmental factors (elevation and 19 bioclimatic variables from Worldclim database) of host beetle collection sites were calculated. These temperatures were significantly correlated with elevation negatively, the maximum temperature of the warmest month (Bio5) positively, and some precipitative variables, especially in the warm season (Bio12, 13, 16, 18) negatively. Sympatric Platycerus kawadai and Platycerus albisomni share the same lineage of yeast symbionts that exhibit the same heat tolerance, but the elevational lower range limit of P. kawadai is higher than that of P. albisomni. Based on the field survey in their sympatric site, the maximum temperature of host wood of P. kawadai larvae is higher about 2–3°C than that of P. albisomni larvae in the summer, which may restrict the elevational range of P. kawadai to higher area. In conclusion, it is suggested that the heat tolerance of yeast symbionts restricts the habitat range of their host Platycerus species or/and that the environmental condition that host Platycerus species prefers affect the heat tolerance of its yeast symbionts. [ABSTRACT FROM AUTHOR]

To deepen understanding the evolutionary process of lucanid–yeast association, the lateral transmission process of yeast symbionts among stag beetle genera Platycerus and Prismognathus around the border between Japan and South Korea was estimated based on molecular analyses and species distribution modelings. Phylogenetic analyses were based on yeast ITS and IGS sequences and beetle COI sequences using Prismognathus dauricus from the Tsushima Islands and Pr. angularis from Kyushu, Japan, as well as other sequence data from our previous studies. The range overlap based on the species distribution model (SDM) and differentiation in ecological space were analyzed. Based on the IGS sequences, Clade II yeast symbionts were shared by Platycerus hongwonpyoi and Pr. dauricus in South Korea and the Tsushima Islands, and Platycerus viridicuprus in Japan. Clade III yeasts were shared by Pr. dauricus from the Tsushima Islands and Pr. angularis in Japan. During the Last Interglacial period when the land bridge between Japan and the Korean Peninsula existed, range overlap was predicted to occur between Pl. viridicuprus and Pr. dauricus in Kyushu and between Pr. dauricus and Pr. angularis in Kyushu and the Tsushima Islands. The ecological space of Pl. hongwonpyoi was differentiated from that of Pl. viridicuprus and Pr. angularis. We demonstrated the paleogeographical lateral transmission process of Scheffersomyces yeast symbionts among lucanid genera and species: putative transmission of yeasts from Pr. dauricus to Pl. viridicuprus in Kyushu and from Pr. angularis to Pr. dauricus in Kyushu or the Tsushima Islands. We also found that the yeast symbionts are likely being replaced in Pr. dauricus on the Tsushima Islands. We present novel estimates of the lateral transmission process of microbial symbionts based on phylogenetic, SDM and environmental analyses among lucanid beetles. [ABSTRACT FROM AUTHOR]

The effects of climate change on species distribution are typically inferred based on species distribution models (SDMs) that do not account for the dispersal ability of species.Here we investigated the utility of dispersal ability measures in predicting the distribution of 10 Platycerus species in Japan, which are cold‐adapted stag beetles sharing ecological and morphological features.We generated three SDMs based on environmental variables without dispersal constraint and incorporating two alternative dispersal constraint scenarios. We compared these three models with respect to SDM performance and the predicted degree of range overlap between neighbouring species. Using the best models among three SDMs, we predicted range shifts under climate change. Additionally, we characterised environmental differences among species distributional areas.Our results revealed that models incorporating dispersal constraints had better predictive performance. Platycerus delicatulus occupied a largest suitable habitat and P. sue had a narrow range in Japan. Most of Platycerus taxa in 2070 were predicted to lose large portions of present suitable areas. Moreover, environment was confirmed to affect the distribution of the targeted species.Incorporating dispersal ability to better understand the effects of climate change on the species ranges is a crucial step towards developing policies for insect management and conservation of vulnerable species. [ABSTRACT FROM AUTHOR]

Accurate evaluation of excess pore water pressure (EPWP) generated in earthquake vibration is a key important factor in seismic engineering against liquefaction. Most previous studies were focused on the relation between cyclic resistance and EPWP developed in the entire liquefaction process. Only a few researchers pointed out that the maximum EPWP ratio accumulated at the first loading cycle, represented by (Δ u / p 0) max− N 1 , was intimately related to the liquefaction resistance of sand. Based on this viewpoint, liquefaction resistance of sandy soils can be improved significantly by repressing EPWP at the first cycle by engineering countermeasures. The relationship between (Δ u / p 0) max− N 1 and liquefaction resistance or the cyclic number to liquefaction N f , however, has not been established quantitatively yet. Moreover, whether this relationship is influenced by stress states such as liquefaction-induced anisotropy, structure or fabric of soils, and loading conditions, is not clear yet. Therefore, a series of undrained cyclic triaxial loading tests were conducted on Toyoura sand, a clean sand famous in Japan, to identify the above-mentioned uncertainties. Based on the test results, a unique empirical (Δ u / p 0) max− N 1 - N f relation was proposed to evaluate the liquefaction resistance. Finally, three typical samples were given to display the application of (Δ u / p 0) max− N 1 - N f relation. • The effect of the pore water pressure accumulated at the first cycle on liquefaction resistance were studied systematically. • A unique relation was proposed to predict liquefaction resistance by the accumulated pore water pressure at the first cycle. • Three engineering applications were employed to illustrate the application of the research finding. [ABSTRACT FROM AUTHOR]