University of the Ryukyus · Center for Research Infrastructure Management

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• A new perspective on the evolution of "Kawara" roof tiles in Ryukyu: A multidisciplinary non-destructive analysis of roof tile transition at Shuri Castle, Ryukyu Islands, Japan.2022 · A unique historical architecture was created at Shuri Castle (Shuri-jo) in the Ryukyu Islands by its "Kawara" roof tiles. After the 13th and 14th centuries, Kawara tiles were introduced to the Ryukyu Islands from several regions, including China, Korea, and mainland Japan, and evolved shapes and patterns that are unique to this island region. However, the transition of some internal features, such as the chemical components and microstructure, had not been analyzed. This study used a multi-faceted approach for such internal data and non-destructive quantitative methods to propose a new perspective on the evolution of historical Ryukyuan Kawara. We analyzed two styles of Ryukyuan Kawara from the 13th to 15th centuries and found that the material processing and firing conditions of the two styles were very similar, even though it had been suggested that they had different origins. A quantitative analysis of tiles from the 16th to 19th centuries revealed a transition in color tone to red, leading to the modern traditional Ryukyuan tiles; traces of changes in firing conditions were also found along with this transition. Finally, the study revealed that the evolution of Ryukyuan Kawara consisted of changed factors, e.g. surface color, and unchanged factors, e.g. paste density. Previous archaeological studies mainly focused on changing external characteristics, such as form and pattern; however, our analysis showed that the internal features changed, while the elemental composition and paste density remained constant from the appearance of the roof tiles until the 19th century. We propose that this is related to different responses of individual factors to external stressors, such as the social context, which may be common to other archaeological artifacts as well. Our study provides a new perspective on the evolution of Ryukyuan Kawara and presents a different discussion of and methods for the chronological study of material culture.
• Population admixtures in medaka inferred by multiple arbitrary amplicon sequencing2022 · Cost-effective genotyping can be achieved by sequencing PCR amplicons. Short 3-10 base primers can arbitrarily amplify thousands of loci using only a few primers. To improve the sequencing efficiency of the multiple arbitrary amplicon sequencing (MAAS) approach, we designed new primers and examined their efficiency in sequencing and genotyping. To demonstrate the effectiveness of our method, we applied it to examining the population structure of the small freshwater fish, medaka (Oryzias latipes). We obtained 2987 informative SNVs with no missing genotype calls for 67 individuals from 15 wild populations and three artificial strains. The estimated phylogenic and population genetic structures of the wild populations were consistent with previous studies, corroborating the accuracy of our genotyping method. We also attempted to reconstruct the genetic backgrounds of a commercial orange mutant strain, Himedaka, which has caused a genetic disturbance in wild populations. Our admixture analysis focusing on Himedaka showed that at least two wild populations had genetically been contributed to the nuclear genome of this mutant strain. Our genotyping methods and results will be useful in quantitative assessments of genetic disturbance by this commercially available strain.
• Non-destructive elemental analysis of prehistoric potsherds in the southern Ryukyu Islands, Japan: Consideration of the pottery surface processing technique in the boundary region between the Japanese Jōmon and Neolithic Taiwan2020 · The southern Ryukyu islands are at the southwest end of the Japanese Archipelago, and can be regarded as boundary region between Japan and Taiwan. Some artifacts with a presumed relationship with Neolithic Taiwan were found, dated to 4,800–3,300 BP. “Shimotabaru-type" pottery in particular could indicate cultural propagation from Taiwan due to similar pottery shapes. Other factors, like manufacturing techniques, have not been discussed much. Interestingly, some of this pottery had a characteristic heterogenous surface structure, which showed the possibility of some surface processing techniques like the slips or paint that is an indicative connection between the Southern Ryukyu Islands and Taiwan. Therefore, in this study, we analyzed this structure on Shimotabaru pottery using nondestructive methods such as X-ray fluorescence microscopy. Chemical analysis revealed that this structure was mainly composed of phosphorus and calcium, which differed from the Neolithic “red-coating" in Taiwan or other surface processing found in surrounding regions. Additionally, we also compared the chemical composition of the potsherd structure with the organic remains and soil associated with the potsherds, and concluded that it was not artificial surface processing but was caused by post-depositional alternation of many faunal remains. To our knowledge, this report is the first case in this region showing a distinct color change in the pottery surface because of coexisting faunal remains. Our results indicated that the heterogenous surface structure of Shimotabaru pottery was not kind of surface treatment but incidental and a result of the post-depositional environment. This result showed the surface processing such as slip or paint had not been developed in the Shimotabaru phase and supported an inconstant and weak cultural relationship the southern Ryukyu islands and surrounding regions, which in turn caused a re-estimation of the previous cultural relationship hypothesis.
• Development of 22 Microsatellite Markers for Assessing Hybridization in the Genus Gekko (Squamata: Gekkonidae)2020 · <p><i>Gekko yakuensis</i> and <i>G. tawaensis</i>, both endemic to western Japan, are threatened by genetic introgression from <i>G. hokouensis</i> and <i>G. japonicus</i>, respectively. To know detailed situation of their hybridizations for planning relevant conservation measures, development of sensitive genetic markers is desired. We here developed microsatellite markers based on the sequences obtained from <i>G. hokouensis</i> using 454 GS Junior sequencer, and tested stability of PCR amplification and species-specificity of alleles at each locus using <i>G. hokouensis</i>, <i>G. yakuensis</i>, <i>G. japonicus</i>, and <i>G. tawaensis</i>. The results showed that 22 loci were almost constantly amplified in more than one species. We further confirmed that there were fixed or nearly fixed allelic displacement between <i>G. hokouensis</i> and <i>G. yakuensis</i>, and between <i>G. japonicus</i> and <i>G. tawaensis</i> at 14 loci. Thus, these 22 loci are considered to be useful for evaluation of hybridizations between these pairs of species.</p>

• 次世代シーケンス解析に基づく土壌動物の生物多様性および機能性評価システムの開発
• 東シナ海南部島嶼地域における新石器文化拡散プロセスの解明
• 先史南琉球をモデルとした「モザイク状境界領域」の形成に関する研究
• 高速DNAシーケンサーによる微小動物の生物多様性モニタリング技術の高精度化

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