Hydroperoxysesquiterpene and lignan constituents of Magnolia kobus

Two new hydroperoxysesquiterpenes, kobusimin A and B, have been isolated from the leaves of Magnolia kobus.     

Reciprocal crosses between Magnolia stellata and Magnolia kobus do not show significant reproductive barriers in seed formation

Congeneric invasive species reduce genetic endemism of native species through hybridization and sometimes cause extinction through genetic or demographic swamping. In the range of Magnolia stellata, a native rare subtree species, Magnolia kobus, an invasive planted/escaped tree species, can also be found. In order to examine possible natural hybridization between the two species, a reciprocal cross-pollination experiment was conducted, and fruit set, seed set, female reproductive success in seed formation (FRS; fruit set × seed set) and seed weight were estimated. With M. stellata as the maternal tree, there were no significant differences in all measurements between intra- and interspecific crosses. With M. kobus as the maternal tree, there were also no significant differences in all measurements except fruit set. These results suggest that there are no reproductive barriers between the two species and planted/escaped M. kobus near the natural habitat of M. stellata presents a threat through hybridization.     

Population genetic structure and historical demography of Oratosquilla oratoria revealed by mitochondrial DNA sequences

Genetic diversity, population genetic structure and molecular phylogeographic pattern of mantis shrimp Oratosquilla oratoria in Bohai Sea and South China Sea were analyzed by mitochondrial DNA sequences. Nucleotide and haplotype diversities were 0.00409?C0.00669 and 0.894?C0.953 respectively. Neighbor-Joining phylogenetic tree clustered two distinct lineages. Both phylogenetic tree and median-joining network showed the consistent genetic structure corresponding to geographical distribution. Mismatch distributions, negative neutral test and ??star-like?? network supported a sudden population expansion event. And the time was estimated about 44000 and 50000 years ago.     

Population structure and dynamics of the clonal dwarf-shrub Linnaea borealis

Abstract. The demography of the long-lived clonal dwarf-shrub Linnaea borealis was studied during four years in a coniferous forest in central Sweden. The main object was to infer patterns of temporal variation in population dynamics of this species. The shoot population is organized in fragments, i.e. physically connected systems of shoots partly covered by the moss carpet. The age and size structure of the fragment population is described, but shoots are more convenient units for a study of population dynamics. A stochastic model of shoot population dynamics was constructed, and simulations indicated a considerable temporal variation in population size and flowering. Hence, variability as such is an essential aspect of the dynamics of established populations of Linnaea. Simulations of extinction risks revealed that small-sized shoot populations (ca. 250 shoots) are likely to be long-lived when experiencing environmentally induced demographic variation of the range observed. Mortality agents for established genets, such as large-scale disturbances, were not incorporated in the models. Some implications of variable population growth rates in clonal plants in woodlands are discussed.     

Isolation and Structure Elucidation of Growth Inhibitors on Silkworm Larvae from Magnolia kobus DC

Two lignans were isolated from leaves of Magnolia kobus DC. as growth inhibitors on silkworm larvae and structurally elucidated as sesamin (I) and kobusin (II) which has been hitherto unknown.     

Population studies: Animal ecology and demography

This concluding survey of the problems considered in the Symposium naturally falls into three sections. In the first brief section certain of the areas in which there is considerable difference in outlook are discussed with a view to ascertaining the nature of the differences in the points of view of workers in different parts of the field; no aspect of the Symposium has been more important than the reduction of areas of dispute. In the second section a rather detailed analysis of one particular problem is given, partly because the question, namely, the nature of the ecological niche and the validity of the principles of niche specificity has raised and continues to raise difficulties, and partly because discussion of this problem gives an opportunity to refer to new work of potential importance not otherwise considered in the Symposium. The third section deals with possible directions for future research. Concluding remarks reprinted from theCold Spring Harbor Symposia on quantitative Biology, Vol. 22, pp. 415–427 (1957) with the permission of the Long Island Biological Association.     

Society, demography and genetic structure in the spotted hyena

Spotted hyenas (Crocuta crocuta) are large mammalian carnivores, but their societies, called 'clans', resemble those of such cercopithecine primates as baboons and macaques with respect to their size, hierarchical structure, and frequency of social interaction among both kin and unrelated group-mates. However, in contrast to cercopithecine primates, spotted hyenas regularly hunt antelope and compete with group-mates for access to kills, which are extremely rich food sources, but also rare and ephemeral. This unique occurrence of baboon-like sociality among top-level predators has favoured the evolution of many unusual traits in this species. We briefly review the relevant socio-ecology of spotted hyenas, document great demographic variation but little variation in social structure across the species' range, and describe the long-term fitness consequences of rank-related variation in resource access among clan-mates. We then summarize patterns of genetic relatedness within and between clans, including some from a population that had recently gone through a population bottleneck, and consider the roles of sexually dimorphic dispersal and female mate choice in the generation of these patterns. Finally, we apply social network theory under varying regimes of resource availability to analyse the effects of kinship on the stability of social relationships among members of one large hyena clan in Kenya. Although social bonds among both kin and non-kin are weakest when resource competition is most intense, hyenas sustain strong social relationships with kin year-round, despite constraints imposed by resource limitation. Our analyses suggest that selection might act on both individuals and matrilineal kin groups within clans containing multiple matrilines.     

Population structure,demography, and dynamics of mountain baboons: An interim report

Counts of 61 baboon troops (Papio cynocephalus ursinus) at four localities in the Drakensberg mountains confirmed earlier reports of a small mean troop size. This troop size of 22.49 animals changed neither with latitude nor elevation. Data from two of the sites suggested that population density increases from south to north, while a working assumption of 2.5 animals/ km² allowed us to set the population size at 7,540 animals, living in 335 troops. Both the adult sex ratio of 2.07 females/male and the immature/ adult female ratio of 1.17 were unaffected by troop size. Repeated counts from nine known troops revealed that the population is at equilibrium. © 1995 Wiley-Liss, Inc.     

Population demography and genetic characteristics of the Pacific Oyster Crassostrea gigas in Japan

The Pacific oyster Crassostrea gigas is a commercially important bivalve distributed along the northwest Pacific coast. Here C. gigas in Japan was investigated using mtDNA and microsatellite markers to elucidate its genetic structure and phylogeny. On the basis of mtDNA all populations showed high genetic diversity with limited genetic differentiation among populations. The pattern of MtDNA diversity suggested that C. gigas had experienced population expansion about 112 Kya, prior to the last glacial maximum (LGM), which accorded well with other marine organisms. For microsatellites, a Bayesian-based assignment test demonstrated that C. gigas is nearly panmictic. However, on the basis of estimates of F_ST, Kumano populations differed significantly from other populations, a recent occurrence based on low R_ST. Irrespective of geographical distance, genetic similarity was observed in the main aquaculture regions with large-scale transportation of cultured spat. Unlike in the Yellow Sea, a genetic bottleneck was not detected in Japanese populations. These results imply, contrary to the prevailing view, that C. gigas in Japan was demographically stable during the LGM. Gene flow by larval dispersal seems to be regionally restricted to localities of congenital areas by ocean currents, while genetic homogenization by cultivated oysters might have occurred in aquaculture areas.     

Spatial genetic structure and historical demography of East Asian wild boar

Pleistocene climatic fluctuations may have had a profound impact on the evolutionary history of many species. The geographical pattern of European wild boar (Sus scrofa) is clearly studied, and it was greatly influenced by ancient climatic events, especially the Last Glacial Maximum. Previous research on genetic variation has mainly focused on the origin and distribution histories of domestic pigs. However, some questions have not been answered, including those concerning the genetic diversity, geographical pattern and possible historic influence of climate on East Asian wild boar (EAWB). Employing the control region of mtDNA (511 bp), we investigated the contributions of historic climate, which possibly shaped the genetic pattern of wild boar. Given that the level of genetic diversity of wild boars is higher in East Asia than in Europe, 172 haplotypes were detected from 680 individuals. Phylogenetic analysis demonstrated the complex phylogeographic structure of EAWB. Mismatch analysis, neutrality tests and the Bayesian Skyline Plot results all retrieved signals of a rapid population expansion, which might have played an important role in driving the formation of complex spatial genetic structure. Genetic data and species distribution modelling showed that the Last Glacial Maximum had weak effect on the distribution of the EAWB. We suggest that, in shaping spatial genetic structure in East Asian, long-term gene flow and population history played more important roles than Pleistocene climate fluctuations.     

Population demography and genetic structure of the fat greenling (Hexagrammos otakii) inferred from mtDNA control region sequence analyses

Pleistocene ice ages in addition to geographical and geological modifications have affected the natural range and habitat of marine organisms in Northwestern Pacific. The effects of glacial events have left a genomic signature, resulting in concordant phylogeographical structures among many species. To investigate the effects of Quaternary climatic changes on the evolution in H. otakii, fragments of 471 bp at the 5′ end of mitochondrial DNA control region were sequenced for 275 individuals from 10 localities in the Northern China and Japan. Both mismatch distribution analyses and neutrality tests suggested recent population expansion (64,000–227,000 years ago). Although estimated value of pairwise population differentiation (F_ST) was low, half (23 of 45) of the comparisons showed statistically significant. Coalescent-based estimates show that gene flow was asymmetric or directional, most of all comparisons (57 of 65) among populations showed low evaluation value of N_m (N_m < 10). Analysis of molecular variance (AMOVA) showed genetic structuring among groups when the data was partitioned into six groups in this study. The defined pattern of genetic variation suggested a crucial role of habitat requirement, marine current, marine gyres and history process. Absence of genetic structure over hundreds of kilometers between AO and assemblage of QD, RZ and GY might imply the common coalescent other than current gene flow. Specific exchange mechanism and fine scale genetic structure need further research using faster evolution molecular markers (microsatellite markers) and further sampling.     

Schistosome population genetic structure: when clumping worms is not just splitting hairs

Schistosomiasis is a major public health problem, affecting over 200 million people worldwide. Although Schistosoma mansoni has been studied rigorously in an attempt to provide a vaccine based on a number of candidate antigens, there has been a lack of complementary effort to determine the range and distribution of variation in representative molecules throughout natural populations. Here, Jason Curtis and Dennis Minchella highlight current (and suggest future) research efforts aimed at assessing genetic variation in schistosome populations, and call for a more robust consideration of schistosome population genetics.     

果生刺盘孢菌Colletotrichum fructicola群体遗传结构研究

研究了10个不同地区Colletotrichum fructicola菌株群体遗传结构。145个病菌样品ITS序列可推导出13种单倍体型(haplotype),其中,Haplotype 5为优势单倍型,有127个菌株。湖北随州地理种群与其他种群遗传分化极大,遗传分化指数(FST)为0.14685–0.40385。AMOVA分析显示,种群间和种群内的遗传变异分别占总变异的13%和87%;Mantel测试显示地理距离与遗传分化没有显著的线性关系;该菌经历过种群扩张,群体间存在有效基因流。     

Sucrose density gradient centrifugation separation of gold and silver nanoparticles synthesized using Magnolia kobus plant leaf extracts

The synthesis and post-synthesis separation of nanoparticles that are polydispersed in size and shape is important due to their variety of applications. In the present study, it is demonstrated that the Magnolia kobus plant extract produces a diverse mixture of extracellular gold and silver nanocrystals with a majority of polydispersed spheres; however, there are a significant number of homogeneously sized triangles, pentagons, and hexagons. The gold and silver nanoparticles synthesized using the M. kobus plant extract can be separated using density gradient centrifugation in the size range of 52 ～ 117 nm and 38 ～ 61 nm, respectively. The average particle sizes increase with increases in the sucrose concentration of each layer. Relatively larger but long, thin plates of gold nanoparticles appear in the higher density sediments, whereas a larger proportion of smaller spheres featured in the lower density gradients. Similarly, silver nanospheres of different sizes are separated at different density gradients with smaller proportions of plates.     

塔里木河上、中游胡杨种群结构与统计分析

在新疆塔里木河的上游-阿瓦提县和中游-轮台县胡杨林自然保护区内设置1．2hm^2的样地,应用相邻格子法进行每木调查获取野外资料,编绘了不同生境胡杨种群的特定时间生命表、存活曲线和大小、年龄结构图。结果表明：不同生境胡杨的种群结构差异明显。阿瓦提县胡杨种群大小、年龄结构呈金字塔型,幼苗储备丰富,缺乏老树,林分较年轻,为增长种群。种群从Ⅰ～Ⅱ级发育过程中死亡率较高,中龄个体生命期望寿命较高,存活曲线符合DeeveyⅢ（凹）型。轮台县胡杨种群大小、年龄结构呈中部大、两端小的正态分布,幼苗相对较少,林相成熟,为稳定种群。种群从Ⅵ～Ⅶ级发育过程中死亡率较高,生命期望寿命随年龄的增大而降低,存活曲线经模型检验符合DeeveyⅡ（直线）型。不同生境种群的消失率与死亡率曲线变化一致,均出现两个高峰,峰值大小明显不同。种群数量动态是胡杨生物学特性和环境条件共同作用的结果。     

Population Graphs: the graph theoretic shape of genetic structure

Patterns of intraspecific genetic variation result from interactions among both historical and contemporary evolutionary processes. Traditionally, population geneticists have used methods such as F-statistics, pairwise isolation by distance models, spatial autocorrelation and coalescent models to analyse this variation and to gain insight about causal evolutionary processes. Here we introduce a novel approach (Population Graphs) that focuses on the analysis of marker-based population genetic data within a graph theoretic framework. This method can be used to estimate traditional population genetic summary statistics, but its primary focus is on characterizing the complex topology resulting from historical and contemporary genetic interactions among populations. We introduce the application of Population Graphs by examining the range-wide population genetic structure of a Sonoran Desert cactus (Lophocereus schottii). With this data set, we evaluate hypotheses regarding historical vicariance, isolation by distance, population-level assignment and the importance of specific populations to species-wide genetic connectivity. We close by discussing the applicability of Population Graphs for addressing a wide range of population genetic and phylogeographical problems.