Origin and spatial population structure of Malagasy native chickens based on mitochondrial DNA.

Since Malagasy human culture became established in a multi-layered way by genetic admixture of Austronesian (Indonesia), Bantu (East Africa) and West Asian populations, the Malagasy native livestock should also have originated from these regions. While recent genetic studies revealed that Malagasy native dogs and goats were propagated from Africa, the origin of Malagasy native chickens is still controversial. Here, we conducted a phylogeographic analysis of the native chickens, focusing on the historical relationships among the Indian Ocean rim countries and based on mitochondrial D-loop sequences. Although previous work suggested that the rare Haplogroup D occurs with high frequencies in Island Southeast Asia-Pacific, East Africa and Madagascar, the major mitochondrial lineage in Malagasy populations is actually not Haplogroup D but the Sub-haplogroup C2, which is also observed in East Africa, North Africa, India and West Asia. We demonstrate that the Malagasy native chickens were propagated directly from West Asia (including India and North Africa), and not via East Africa. Furthermore, they display clear genetic differentiation within Madagascar, separated into the Highland and Lowland regions as seen in the human genomic landscape on this island. Our findings provide new insights for better understanding the intercommunion of material/non-material cultures within and around Madagascar.

Climate heterogeneity shapes phylogeographic pattern of Hippophae gyantsensis (Elaeagnaceae) in the east Himalaya-Hengduan Mountains.

The interaction of recent orographic uplift and climate heterogeneity acted as a key role in the East Himalaya-Hengduan Mountains (EHHM) has been reported in many studies. However, how exactly the interaction promotes clade diversification remains poorly understood. In this study, we both used the chloroplast trnT-trnF region and 11 nuclear microsatellite loci to investigate the phylogeographic structure and population dynamics of Hippophae gyantsensis and estimate what role geological barriers or ecological factors play in the spatial genetic structure. The results showed that this species had a strong east-west phylogeographic structure, with several mixed populations identified from microsatellite data in central location. The intraspecies divergence time was estimated to be about 3.59 Ma, corresponding well with the recent uplift of the Tibetan Plateau. Between the two lineages, there was significant climatic differentiation without geographic barriers. High consistency between lineage divergence, climatic heterogeneity, and Qingzang Movement demonstrated that climatic heterogeneity but not geographic isolation drives the divergence of H. gyantsensis, and the recent regional uplift of the QTP, as the Himalayas, creates heterogeneous climates by affecting the flow of the Indian monsoon. The east group of H. gyantsensis experienced population expansion c. 0.12 Ma, closely associated with the last interglacial interval. Subsequently, a genetic admixture event between east and west groups happened at 26.90 ka, a period corresponding to the warm inter-glaciation again. These findings highlight the importance of the Quaternary climatic fluctuations in the recent evolutionary history of H. gyantsensis. Our study will improve the understanding of the history and mechanisms of biodiversity accumulation in the EHHM region.

Phylogenomic analyses of Camellia support reticulate evolution among major clades.

Camellia (Theaceae) is a morphologically highly diverse genus of flowering plants and includes many famous species with high economic value, and the phylogeny of this genus is not fully resolved. We used 95 transcriptomes from 87 Camellia species and identified 1481 low-copy genes to conduct a detailed analysis of the phylogeny of this genus according to various data-screening criteria. The results show that, very different from the two existing classification systems of Camellia, 87 species are grouped into 8 main clades and two independent species, and that all 8 clades except Clade 8 were strongly supported by almost all the coalescent or concatenated trees using different gene subsets. However, the relationships among these clades were weakly supported and different from analyses using different gene subsets; furthermore, they do not agree with the phylogeny from chloroplast genomes of Camellia. Additional analyses support reticulate evolution (probably resulting from introgression or hybridization) among some major Camellia lineages, providing explanation for extensive gene tree conflicts. Furthermore, we inferred that together with the formation of East Asian subtropical evergreen broad-leaved forests, Camellia underwent a radiative divergence of major clades at 23 âˆ¼ 19 Ma in the late Miocene then had a subsequent species burst at 10 âˆ¼ 5 Ma. Principal component and cluster analyses provides new insights into morphological changes underlying the evolution of Camellia and a reference to further clarify subgenus and sections of this genus. The comprehensive study here including a nuclear phylogeny and other analyses reveal the rapid evolutionary history of Camellia.

Evolution of snow algae, from cosmopolitans to endemics, revealed by DNA analysis of ancient ice.

Recent studies of microbial biogeography have revealed the global distribution of cosmopolitans and dispersal of regional endemics, but little is known about how these processes are affected by microbial evolution. Here, we compared DNA sequences from snow/glacier algae found in an 8000-year-old ice from a glacier in central Asia with those from modern snow samples collected at 34 snow samples from globally distributed sites at the poles and mid-latitudes, to determine the evolutionary relationship between cosmopolitan and endemic phylotypes of snow algae. We further applied a coalescent theory-based demographic model to the DNA sequences. We found that the genus Raphidonema (Trebouxiophyceae) was distributed over both poles and mid-latitude regions and was detected in different ice core layers, corresponding to distinct time periods. Our results indicate that the modern cosmopolitan phylotypes belonging to Raphidonema were persistently present long before the last glacial period. Furthermore, endemic phylotypes originated from ancestral cosmopolitan phylotypes, suggesting that modern regional diversity of snow algae in the cryosphere is a product of microevolution. These findings suggest that the cosmopolitans dispersed across the world and then derived new localized endemics, which thus improves our understanding of microbial community formation by microevolution in natural environments.

Complete Mitochondrial Genome Analysis Clarifies the Enigmatic Origin of Haplogroup D in Japanese Native Chickens.

Japanese native chickens (JNCs) comprise approximately 50 breeds, making Japan a diversity hotspot for native chicken breeds. JNCs were established through the repeated introduction of chickens from foreign countries. Jidori, which is the generic name of JNC breeds whose ancestral morphology resembles that of their wild progenitor (red junglefowls), is generally thought to have propagated from north East Asia (Korea and north China) to ancient Japan. However, mitochondrial haplogroup D, which is abundant in Island Southeast Asia (ISEA) as well as the Pacific but relatively rare in other regions, can be observed in some Jidori breeds (e.g., Tosa-Jidori, Tokuji-Jidori) with high frequency, leading to speculation that chickens from ISEA or the Pacific also contributed genetically to JNCs. To test this hypothesis, we sequenced the mitochondrial genomes of Jidori breeds and conducted phylogeographic analysis. Our results indicate that the JNC Haplogroup D belongs to Sub-haplogroup D2, which is currently only observed in Xinjiang, northwest China, and not to Sub-haplogroup D1, which is widely distributed in the ISEA-Pacific region. The other mitochondrial haplogroups of Jidori examined in this study also showed affinity to those of chickens native to north East Asia. Therefore, our findings support the north East Asian origin hypothesis for Jidori.

Comprehensive assessment of genetic diversity, structure, and relationship in four Japanese cattle breeds by Illumina 50 K SNP array analysis.

There are four unique cattle breeds in Japan: Japanese Black, Japanese Brown, Japanese Polled, and Japanese Shorthorn. The objective of this study was to comprehensively assess the genetic diversity, structure, relationship, and the degree of influence from foreign breeds (Angus, Simmental, Hanwoo, Shorthorn, Ayrshire, Brown Swiss, and Devon) in the Japanese cattle breeds using Illumina 50 K SNP array. In principal component analysis, each Japanese breed was separately clustered except for Japanese Shorthorn and Shorthorn. Japanese cattle breeds also showed different genetic components from each other at K ≥ 5 in population structure analysis. Japanese Shorthorn, on the other hand, had a very similar structure to Shorthorn at K ≤ 9, and Japanese Polled had a partially similar component with Angus at K = 3-7. Such close relationships were also observed in the phylogenetic tree. These findings imply that Japanese cattle breeds share genetic components with European cattle breeds to some extent while they have been almost differentiated. In population structure analysis, Japanese Black cattle shared little genetic component (3.5%) with European breeds. This is the first study to determine the extent to which European breeds impact Japanese breeds.

Phylogenomics and Spatiotemporal Dynamics of Bovine Leukemia Virus Focusing on Asian Native Cattle: Insights Into the Early Origin and Global Dissemination.

Bovine leukemia virus (BLV), the causative agent of enzootic bovine leukosis, is currently one of the most important pathogens affecting the cattle industry worldwide. Determining where and in which host it originated, and how it dispersed across continents will provide valuable insights into its historical emergence as the cattle pathogen. Various species in the Bos genus were domesticated in Asia, where they also diversified. As native cattle (taurine cattle, zebu cattle, yak, and water buffalo) are indigenous and adapted to local environments, we hypothesized that Asian native cattle could have harbored BLV and, therefore, that they were important for virus emergence, maintenance, and spread. In this study, phylogeographic and ancestral trait analyses-including sequences obtained from Asian native cattle-were used to reconstruct the evolutionary history of BLV. It was shown that, since its probable emergence in Asia, the virus spread to South America and Europe via international trade of live cattle. It was inferred that zebu cattle were the hosts for the early origin of BLV, while taurine cattle played the significant role in the transmission worldwide. In addition, the results of positive selection analysis indicate that yak had a substantially minor role in the transmission of this virus. In this study, endogenous deltaretrovirus sequences in bats, collected in Asian countries, were also analyzed on whether these sequences were present in the bat genome. Endogenous deltaretrovirus sequences were detected from bat species endemic to specific regions and geographically isolated for a long time. Endogenous deltaretrovirus sequences from these geographically isolated species represent ancient exogenous deltaretroviruses distributions. The phylogenetic analysis revealed that these newly obtained endogenous deltaretrovirus sequences were closely related to those of BLV from Asian native cattle, indicating that BLV-related ancient deltaretroviruses circulated in Asia long before the emergence of BLV. Together, our analyses provide evidence for origin and spatiotemporal dynamics of BLV.

Paleogenomics reveals independent and hybrid origins of two morphologically distinct wolf lineages endemic to Japan.

Little is known about the spatiotemporal dynamics of gray wolves in the Pleistocene across low-latitude regions of Eurasia. In Japan, a small-bodied endemic subspecies of Japanese wolves existed and went extinct in the early 1900s. The fossil record indicates that a giant wolf, which reached 70 cm in body height, inhabited Japan during the Pleistocene, but its evolutionary relationship, if any, with the Japanese wolf remains uncertain. Here, to reveal the genetic origin of the Japanese wolf, we analyzed ancient DNA from remains (recovered in Japan) of one Pleistocene wolf that lived 35,000 years ago and one Holocene wolf from 5,000 years ago. The analysis of the mitochondrial DNA revealed that the Pleistocene wolf was not part of the Japanese wolf clade but rather an earlier-diverging lineage. The analysis of the nuclear DNA of the Holocene Japanese wolf revealed that it was an admixture of the Japanese Pleistocene wolf and continental wolf lineages. These findings suggest that the Japanese wolf originated via waves of colonization of multiple Pleistocene wolf populations at 57-35 and 37-14 ka, respectively, followed by interpopulation hybridization.

Molecular Evolutionary Rate Predicts Intraspecific Genetic Polymorphism and Species-Specific Selection.

It is unknown what determines genetic diversity and how genetic diversity is associated with various biological traits. In this work, we provide insight into these issues. By comparing genetic variation of 14,671 mammalian gene trees with thousands of individual human, chimpanzee, gorilla, mouse, and dog/wolf genomes, we found that intraspecific genetic diversity can be predicted by long-term molecular evolutionary rates rather than de novo mutation rates. This relationship was established during the early stage of mammalian evolution. Moreover, we developed a method to detect fluctuations of species-specific selection on genes based on the deviations of intraspecific genetic diversity predicted from long-term rates. We showed that the evolution of epithelial cells, rather than connective tissue, mainly contributed to morphological evolution of different species. For humans, evolution of the immune system and selective sweeps caused by infectious diseases are the most representative examples of adaptive evolution.

Fine-scale genetic diversity and putative ecotypes of oxymonad protists coinhabiting the hindgut of Reticulitermes speratus.

The hindgut of lower termites is generally coinhabited by multiple morphologically identifiable protist species. However, it is unclear how many protist species truly coexist in this miniaturized environment, and moreover, it is difficult to define the fundamental unit of protist diversity. Species delineation of termite gut protists has therefore been guided without a theory-based concept of species. Here, we focused on the hindgut of the termite Reticulitermes speratus, where 10 or 11 morphologically distinct oxymonad cell types, that is, morphospecies, coexist. We elucidated the phylogenetic structure of all co-occurring oxymonads and addressed whether their diversity can be explained by the "ecotype" hypothesis. Oxymonad-specific 18S rRNA gene amplicon sequencing analyses of whole-gut samples, combined with single-cell 18S rRNA sequencing of the oxymonad morphospecies, identified 210 one-nucleotide-level variants. The phylogenetic analysis of these variants revealed the presence of microdiverse clusters typically within 1% sequence divergence. Each known oxymonad morphospecies comprised one to several monophyletic or paraphyletic microdiverse clusters. Using these sequence data sets, we conducted computational simulation to predict the rates of ecotype formation and periodic selection, and to demarcate putative ecotypes. Our simulations suggested that the oxymonad genetic divergence is constrained primarily by strong selection, in spite of limited population size and possible bottlenecks during intergenerational transmission. A total of 33 oxymonad ecotypes were predicted, and most of the putative ecotypes were consistently detected among different colonies and host individuals. These findings provide a possible theoretical basis for species diversity and underlying mechanisms of coexistence of termite gut protists.

Comparative morphological study of skeletal muscle weight among the red jungle fowl (Gallus gallus) and various fowl breeds (Gallus domesticus).

We examined the weight distribution of skeletal muscles of the red jungle fowl, then compared these values with those of domesticated populations to determine how muscle distribution has changed by selecting breeding. Sonia, Fayoumi, and Rhode Island Red were selected for comparison from livestock breeds, while Japanese Shamo and Thai fighting cocks were selected from cockfighting groups. Principal component analysis was applied using body size-free data. The mass distribution of muscles clearly differed between the wild, livestock, and cockfighting groups, demonstrating that muscle distribution has changed after selecting breeding, coupled with functional demands of each group. The red jungle fowl, which has the ability to fly, could be clearly distinguished from the flightless domesticated populations due to differences in flight pectoral muscle size. The cervical muscles in the wild population were smaller than in the domesticated groups; these do not contribute to flight. The gluteal muscles were larger in the fighting cock group, functionally coupled to their traditionally preferred upright posture. Wild bird populations typically exhibit reduced weight of their hind limbs, associated with flight, but as the red jungle fowl displays largely terrestrial behavior, these muscles are similar in arrangement and relative size to those of the livestock groups. We showed that the mass distribution pattern of skeletal muscles expresses selecting breeding strategy and clearly reflects the specific traits for each group.

Ancient DNA reveals multiple origins and migration waves of extinct Japanese brown bear lineages.

Little is known about how mammalian biogeography on islands was affected by sea-level fluctuations. In the Japanese Archipelago, brown bears (Ursus arctos) currently inhabit only Hokkaido, the northern island, but Pleistocene fossils indicate a past distribution throughout Honshu, Japan's largest island. However, the difficulty of recovering ancient DNA from fossils in temperate East Asia has limited our understanding of their evolutionary history. Here, we analysed mitochondrial DNA from a 32 500-year-old brown bear fossil from Honshu. Our results show that this individual belonged to a previously unknown lineage that split approximately 160 Ka from its sister lineage, the southern Hokkaido clade. This divergence time and fossil record suggest that brown bears migrated from the Eurasian continent to Honshu at least twice; the first population was an early-diverging lineage (greater than 340 Ka), and the second migrated via Hokkaido after approximately 160 Ka, during the ice age. Thus, glacial-age sea-level falls might have facilitated migrations of large mammals more frequently than previously thought, which may have had a substantial impact on ecosystem dynamics in these isolated islands.

Evolution of Reproductive Life History in Mammals and the Associated Change of Functional Constraints.

Phylogenetic trees based on multiple genomic loci enable us to estimate the evolution of functional constraints that operate on genes based on lineage-specific fluctuation of the evolutionary rate at particular gene loci, "gene-branch interactions". Using this information as predictors, our previous work inferred that the common ancestor of placental mammals was nocturnal, insectivorous, solitary, and bred seasonally. Here, we added seven new continuous traits including lifespan, bodyweight, and five reproduction-related traits and inferred the coevolution network of 14 core life history traits for 89 mammals. In this network, bodyweight and lifespan are not directly connected to each other; instead, their correlation is due to both of them coevolving with gestation period. Diurnal mammals are more likely to be monogamous than nocturnal mammals, while arboreal mammals tend to have a smaller litter size than terrestrial mammals. Coevolution between diet and the seasonal breeding behavior test shows that year-round breeding preceded the dietary change to omnivory, while seasonal breeding preceded the dietary change to carnivory. We also discuss the evolution of reproductive strategy of mammals. Genes selected as predictors were identified as well; for example, genes function as tumor suppressor were selected as predictors of weaning age.

Complete mitochondrial genome sequence of Tosa-Jidori sheds light on the origin and evolution of Japanese native chickens.

OBJECTIVE: In Japan, approximately 50 breeds of indigenous domestic chicken, called Japanese native chickens (JNCs), have been developed. JNCs gradually became established based on three major original groups, "Jidori", "Shoukoku", and "Shamo". Tosa-Jidori is a breed of Jidori, and archival records as well as its morphologically primitive characters suggest an ancient origin. Although Jidori is thought to have been introduced from East Asia, a previous study based on mitochondrial D-loop sequences demonstrated that Tosa-Jidori belongs to haplogroup D, which is abundant in Southeast Asia but rare in other regions, and a Southeast Asian origin for Tosa-Jidori was therefore suggested. The relatively small size of the D-loop region offers limited resolution in comparison with mitogenome phylogeny. This study was conducted to determine the phylogenetic position of the Tosa-Jidori breed based on complete mitochondrial D-loop and mitogenome sequences, and to clarify its evolutionary relationships, possible maternal origin and routes of introduction into Japan. METHODS: Maximum likelihood and parsimony trees were based on 133 chickens and consisted of 86 mitogenome sequences as well as 47 D-loop sequences. RESULTS: This is the first report of the complete mitogenome not only for the Tosa-Jidori breed, but also for a member of one of the three major original groups of JNCs. Our phylogenetic analysis based on D-loop and mitogenome sequences suggests that Tosa-Jidori individuals characterized in this study belong to the haplogroup D as well as the sub-haplogroup E1. CONCLUSION: The sub-haplogroup E1 is relatively common in East Asia, and so although the Southeast Asian origin hypothesis cannot be rejected, East Asia is another possible origin of Tosa-Jidori. This study highlights the complicated origin and breeding history of Tosa-Jidori and other JNC breeds.

Concerted and birth-and-death evolution of 26S ribosomal DNA in Camellia L.

BACKGROUND AND AIMS: The ribosomal DNA (rDNA) gene family, encoding ribosomal RNA (rRNA), has long been regarded as an archetypal example illustrating the model of concerted evolution. However, controversy is arising, as rDNA in many eukaryotic species has been proved to be polymorphic. Here, a metagenomic strategy was applied to detect the intragenomic polymorphism as well as the evolutionary patterns of 26S rDNA across the genus Camellia. METHODS: Degenerate primer pairs were designed to amplify the 26S rDNA fragments from different Camellia species. The amplicons were then paired-end sequenced on the Illumina MiSeq platform. KEY RESULTS: An extremely high level of rDNA polymorphism existed universally in Camellia. However, functional rDNA was still the major component of the family, and was relatively conserved among different Camellia species. Sequence variations mainly came from rRNA pseudogenes and favoured regions that are rich in GC. Specifically, some rRNA pseudogenes have existed in the genome for a long time, and have even experienced several expansion events, which has greatly enriched the abundance of rDNA polymorphism. CONCLUSIONS: Camellia represents a group in which rDNA is subjected to a mixture of concerted and birth-and-death evolution. Some rRNA pseudogenes may still have potential functions. Conversely, when released from selection constraint, they can evolve in the direction of decreasing GC content and structural stability through a methylation-induced process, and finally be eliminated from the genome.

Cattle mitogenome variation reveals a post-glacial expansion of haplogroup P and an early incorporation into northeast Asian domestic herds.

Surveys of mitochondrial DNA (mtDNA) variation have shown that worldwide domestic cattle are characterized by just a few major haplogroups. Two, T and I, are common and characterize Bos taurus and Bos indicus, respectively, while the other three, P, Q and R, are rare and are found only in taurine breeds. Haplogroup P is typical of extinct European aurochs, while intriguingly modern P mtDNAs have only been found in northeast Asian cattle. These Asian P mtDNAs are extremely rare with the exception of the Japanese Shorthorn breed, where they reach a frequency of 45.9%. To shed light on the origin of this haplogroup in northeast Asian cattle, we completely sequenced 14 Japanese Shorthorn mitogenomes belonging to haplogroup P. Phylogenetic and Bayesian analyses revealed: (1) a post-glacial expansion of aurochs carrying haplogroup P from Europe to Asia; (2) that all Asian P mtDNAs belong to a single sub-haplogroup (P1a), so far never detected in either European or Asian aurochs remains, which was incorporated into domestic cattle of continental northeastern Asia possibly ~ 3700 years ago; and (3) that haplogroup P1a mtDNAs found in the Japanese Shorthorn breed probably reached Japan about 650 years ago from Mongolia/Russia, in agreement with historical evidence.

Indonesian native goats (Capra hircus) reveal highest genetic frequency of mitochondrial DNA haplogroup B in the world.

The objective of this study was to determine mtDNA sequences of the 481 bp HV1 region from two Indonesian native goat breeds, Kacang and Marica, to confirm the phylogeographic distribution of caprine haplogroup B in Southeast Asia. Based on these sequences, 12 haplotypes were observed and categorized into the predominant haplogroup B and minority haplogroup A, indicating that Indonesian native goats present the highest frequency (0.950) of the haplogroup B in the world. These results strongly emphasize previous observations of the haplogroup B frequencies tending to increase southeastward in Southeast Asia. Additionally, this suggests that goats primary bred into Southeast Asia might predominantly carry haplogroup B. This could essentially contribute to the understanding of the origin, propagation route and/or introgression history of Southeast Asian goats.

Evaluation of reported sediment samples from 20 Ma using a molecular phylogenetic approach: comment on Liu et al. (2017).

Liu et al. reported the cultivation and DNA sequencing of 69 fungal isolates (Ascomycota and Basidiomycota) from ancient subseafloor sediments, suggesting that they represent living fungal populations that have persisted for over 20 million years. Because these findings could bring about a paradigm shift in our understanding of the spatial breadth of the deep subsurface biosphere as well as the longevity of ancient DNA, it is extremely important to verify that their samples represent pure ancient fungi from 20 million years ago without contamination by modern species. For this purpose, we estimated the divergence times of Dikarya (Ascomycota + Basidiomycota) and Mucoromycota fungi assuming that the fungal isolates were actually sampled from 20 Ma (mega-annum) sediments and evaluated the validity of the sample ages. Using this approach, we estimate that the age of the last common ancestor of Dikarya and Mucoromycota fungi greatly exceeds the age of the Earth. Our finding emphasizes the importance of using reliable approaches to confirm the dating of ancient samples.

Maternal phylogeographic patterns and coalescent times of Arabidopsis thaliana based on chloroplast DNA analyses.

Arabidopsis thaliana, one of the most important model plants, has played an essential role in every biological field including evolutionary biology. Recent population genomic studies have gradually clarified the origin and evolution of this species. Nevertheless, incongruent patterns among gene trees based on cytogenetic data have highlighted the importance of understanding the life history evolution and landscape biogeography of extant A. thaliana populations. Here, we focus on the maternally inherited chloroplast genome in A. thaliana and carry out phylogeographic analyses and coalescent time estimations. The maternal lineage of A. thaliana originated in the European to West and Central Asian regions in the Early Pleistocene. Relicts, the ancient lineages suggested by population genomic data, are not ancestral maternal lineages, but are derived from the European population. Part of the European population then dispersed eastward and spread to the Indian region, and finally extended to the Yangtze River region. The branching patterns and evolutionary time scales of the maternal genealogy are significantly different from those estimated from analyses of autosomal genes, and these cannot be explained by incomplete lineage sorting of the ancestral polymorphisms during the coalescent process due to large differences in the evolutionary time scale involved.

Community-Wide Dissemination of Bystander Cardiopulmonary Resuscitation and Automated External Defibrillator Use Using a 45-Minute Chest Compression-Only Cardiopulmonary Resuscitation Training.

Background Little is known about whether cardiopulmonary resuscitation ( CPR ) training can increase bystander CPR in the community or the appropriate target number of CPR trainings. Herein, we aimed to demonstrate community-wide aggressive dissemination of CPR training and evaluate temporal trends in bystander CPR . Methods and Results We provided CPR training (45-minute chest compression-only CPR plus automated external defibrillator use training or the conventional CPR training), targeting 16% of residents. All emergency medical service-treated out-of-hospital cardiac arrests of medical origin were included. Data on patients experiencing out-of-hospital cardiac arrest and bystander CPR quality were prospectively collected from September 2010 to December 2015. The primary outcome was the proportion of high-quality bystander CPR . During the study period, 57 173 residents (14.7%) completed the chest compression-only CPR training and 32 423 (8.3%) completed conventional CPR training. The proportion of bystander CPR performed did not change (from 43.3% in 2010 to 42.0% in 2015; P for trend=0.915), but the proportion of high-quality bystander CPR delivery increased from 11.7% in 2010 to 20.7% in 2015 ( P for trend=0.015). The 1-year increment was associated with high-quality bystander CPR (adjusted odds ratio, 1.461; 95% CI, 1.055-2.024). Bystanders who previously experienced CPR training were 3.432 times (95% CI, 1.170-10.071) more likely to perform high-quality CPR than those who did not. Conclusions We trained 23.0% of the residents in the medium-sized city of Osaka, Japan, and demonstrated that the proportion of high-quality CPR performed on the scene increased gradually, whereas that of bystander CPR delivered overall remained stable.