Search Results (6)

South China’s freshwater biodiversity has been shaped by Quaternary climatic oscillations and persistent geological barriers. We investigated the phylogeography and conservation implications of the primary freshwater fish Microphysogobio kachekensis across mainland China and Hainan Island using mitochondrial (cyt b and control region) and nuclear (RAG2 and rpS7-1) markers from 200 individuals. Mitochondrial analyses recovered two major lineages and multiple sublineages largely structured by drainage basins, whereas nuclear data resolved four geographically concordant lineages. Population differentiation was strong (high F_ST), and SAMOVA/AMOVA supported major barriers restricting gene flow, including the Qiongzhou Strait, Gulf of Tonkin, Yunkai Mountains, and Nanling Mountains. Ancestral-area reconstruction inferred the Pearl River region as the most likely source area, followed by dispersal to northern Hainan and subsequent expansion to southern Hainan and the Red River, with additional northward expansion to the Zhejiang–Fujian region. Despite high haplotype diversity, within-population nucleotide diversity was low, consistent with long-term river isolation and complex demographic history. We propose six ESUs and four MUs for evolutionarily informed conservation and to guide stock enhancement in southern China. Full article

The Japanese archipelago as a continental island of the Eurasia continent and harboring high levels of plant species diversity provides an ideal geographical setting for investigating vicariant allopatric speciation due to the sea-level fluctuations associated with climatic oscillations during the Quaternary. In this study, three chloroplast DNA regions and 14 nuclear loci were sequenced for 31 individuals from three populations of Torreya nucifera var. nucifera and 52 individuals from three populations of T. nucifera var. radicans. Population genetic analyses (Network, STRUCTURE and phylogeny) revealed that the genetic boundaries of the two varieties are distinct, with high genetic differentiation (F_ST) of 0.9619 in chloroplast DNA and 0.6543 in nuclear loci. The relatively ancient divergence times between the two varieties were estimated to 3.03 Ma by DIYABC and 1.77 Ma by IMa2 when dated back to the late Pliocene and the early Pleistocene, respectively. The extremely weak gene flow (2Nm = 0.1) between the two varieties was detected by IMa2, which might be caused by their population expansion since the early Pleistocene (~2.0 Ma) inferred in the Bayesian skyline plots and DIYABC. Niche modeling showed that the two varieties had significant ecological differentiation (p < 0.001) since the Last Interglacial even earlier. These results demonstrate that vicariant allopatric speciation due to sea-level fluctuations may be a common mode of speciation in the Japanese archipelago. This finding provides insights into the understanding of species diversification in the Japanese Archipelago and even East Asian flora under climatic oscillations during the Quaternary. Full article

The genetic structure and demographic history of marine organisms are influenced by biological and ecological features, oceanic currents, and the paleo-geological effects of sea-level fluctuations. In this study, we used mitochondrial COI + 16S gene analysis to investigate the phylogeographic pattern and demography of Monodonta labio and M. confusa in Taiwan, the Ryukyu Islands, Japan, mainland China, and Korea. Our genetic analysis identified two major lineages that were not evident from the distribution patterns of different populations. The Taiwan Strait, which acted as a land bridge during Pleistocene glaciations, and the lack of strong dispersal barriers to gene flow between ocean basins after glaciations shaped the phylogeographic pattern. The genetic differentiation in the Ryukyu Islands was influenced by the specialist-generalist variation hypothesis and the Kuroshio Current. Bayesian skyline plot analyses suggested that the effective population size of M. labio and M. confusa rapidly increased approximately 0.1 and 0.075 million years ago, respectively. Our approximate Bayesian computation analysis suggested that all M. labio and M. confusa populations experienced a decline in population size following a recent population expansion and constant size, respectively. Our study provides a baseline for future investigations of the biogeographical patterns of marine gastropods in the Northwest Pacific and offers valuable insights for the management, sustainable resource utilization, and conservation of this species. Full article

Schistosomiasis is still one of the most significant neglected tropical diseases worldwide, and China is endemic for Schistosoma japonicum. With its great achievement in schistosomiasis control, the government of China has set the goal to eliminate the parasitic disease at the country level by 2030. However, one major challenge is the remaining huge areas of habitats for the intermediate host Oncomelania hupensis. This is further exacerbated by an increasing number of new emerging snail habitats reported each year. Therefore, population genetics on snails in such areas will be useful in evaluation of snail control effect and/or dispersal. We then sampled snails from new emerging habitats in Taicang of Jiangsu, China, a currently S. japonicum non-endemic area from 2014 to 2017, and performed population genetic analyses based on nine microsatellites. Results showed that all snail populations had low genetic diversity, and most genetic variations originated from within snail populations. The estimated effective population size for the 2015 population was infinitive. All snails could be separated into two clusters, and further DIYABC analysis revealed that both the 2016 and the 2017 populations may derive from the 2015, indicating that the 2017 population must have been missed in the field survey performed in 2016. These findings may have implications in development of more practical guidelines for snail monitoring and control. Full article

The ichthyofauna of continental islands is characterized by immigration through a land bridge due to fluctuating sea levels. Hainan Island is adjacent to the southern margin of mainland China and provides opportunities for understanding the origin and diversification of freshwater fishes. The aim of our study was to evaluate the level of genetic variation and phylogeographic structure of Opsariichthys hainanensis on Hainan Island and mainland China, using mtDNA cyt b gene (1140 bp) and D-loop (926 bp), nuclear RAG1 gene (1506 bp), and 12 microsatellite loci. Mitochondrial phylogenetic analysis identified five major lineages according to the geographical distribution from different populations. We suggested that two dispersal events occurred: the population in the Changhua River migrated to the Red River (Lineage B), and the populations in the South Hainan region moved northwards to the North Hainan region. However, populations in Northwest Hainan Island dispersed to the populations around the Gulf of Tonkin (Lineage A1) and populations in Northeast Hainan Island dispersed to the populations in mainland China (Lineage A2). Our results indicated that the populations of O. hainanensis suffered a bottleneck event followed by a recent population expansion supported by the ABC analysis. We suggest that O. hainanensis populations were found mostly in the lowlands and a lack of suitable freshwater habitat in southern mainland China and Hainan during the Last Interglacial period, and then expansion occurred during the Last Glacial Maximum. Full article

Oceanic currents, biological traits, and geological evidence from historical climate change have shaped the distribution of genetic diversity and demographic history in Macrobrachium japonicum. In this study, we investigated the phylogeographic structures and demographic history of M. japonicum in Taiwan and the Ryukyu Islands by the partial mitochondrial COI gene. The topology of the haplotype minimum-spanning network revealed a star-like structure, which suggested a recent range expansion. With the apparent lack of strong dispersal barriers to gene flow between ocean basins, amphidromous prawns, as marine organisms with larvae of high dispersal abilities, are generally expected to show genetic homogeneity. Divergence data suggested that M. japonicum populations diverged 0.462 ± 0.164 myr. Complex patterns of asymmetrical gene flow indicate that variation in dispersal ability is affected by the dominant Kuroshio Current systems of the Pacific Ocean. Analysis of its demographic history revealed that M. japonicum underwent a decline in size following a recent population expansion based on ABC analysis. Bayesian skyline plot analyses of all populations indicated that the expansion of M. japonicum was estimated to have occurred in 175 Kya and that the effective population size rapidly increased by approximately 50 Kya. The results of this study may offer both practical and theoretical value for the further study of conservation genetics, management, and sustainable resource utilization. Full article