七筋菇自然居群的遗传结构分析

采用ISSR分子标记,对七筋菇(Clintonia udensis)17个居群的遗传多样性与遗传结构进行了研究。结果表明:七筋菇不同居群的多态位点百分率PPB为11.90%~59.52%,总的多态位点百分率PPB为98.8%,具有高的遗传多样性。Shannon多样性指数(0.6903)和基因分化系数(GST=0.6944)均揭示出七筋菇居群间存在明显的遗传差异,AMOVA分析结果也显示遗传变异主要发生在居群之间(81.47%),而居群内部的遗传变异仅为18.53%。七筋菇居群间的遗传距离从0.1871~0.6632,平均为0.3838,大于同一物种居群间的平均遗传距离值(0.05),同样表明七筋菇居群间的遗传多样性存在较大差异。七筋菇居群间的基因流Nm=0.2200,远远低于一般广布种植物的基因流(Nm=1.881)。Mantel检测显示居群间的遗传距离与地理距离之间没有显著相关性(r=0.029,P=0.3196)。七筋菇分布范围广以及其进化历史是其具有高遗传多样性的原因;居群间存在较高遗传变异可能是由于七筋菇本身的生物学特性、有限的基因流以及遗传漂变等原因造成的。     

大别山山核桃天然群体遗传结构的初步分析

利用RAPD分子标记技术检测了大别山山核桃3个天然居群的遗传多样性和遗传结构。20条10 bp随机引物共检测到238个扩增位点,其中多态性位点162个,多态位点百分率(PPB)为68.1%。居群水平Shannon’s多态性信息指数(I)介于0.2651~0.2801之间;居群水平Ne i’s基因多样性指数(H)介于0.1789~0.1890之间。遗传变异计算显示大别山山核桃居群间基因分化系数(Gst)为0.4063,分子方差分析(AMOVA)表明居群间基因分化水平为0.4177,居群间基因流(Nm)为0.7306,说明大别山山核桃大部分变异存在于居群内,居群间基因交流相对较少。这一结果符合大别山山核桃风媒、异交的繁育系统特点,但其居群间基因分化程度明显高于异交植物的平均水平(Gst=0.1930)。地理隔离、居群内近交及居群间基因流受阻可能是形成目前大别山山核桃天然群体遗传结构的主要因素。     

濒危植物连香树居群的遗传多样性和遗传分化研究

利用ISSR分子标记技术对濒危植物连香树10个居群的遗传多样性和遗传变异进行了分析,结果表明:连香树物种水平遗传多样性较高,多态位点百分率(PPB)达到69.59%,Nei’s基因多样性指数(H)和Shannon信息指数(I)分别为0.231 3和0.351 4;而在居群水平上,多态位点百分率(PPB)为30.61%,Nei’s基因多样性指数(H)和Shannon信息指数(I)分别为0.115 6和0.173 3。遗传变异分析表明,居群间遗传分化程度高,遗传分化系数(GST)为0.500 3,居群间基因流Nm为0.527 3。Mantel检测,居群间的遗传距离和地理距离之间不存在显著的相关性。生境的片断化使居群间的基因流受阻,可能是导致居群间高遗传分化和居群水平低遗传多样性的主要原因。     

长筒石蒜居群遗传多样性RAPD分析

利用RAPD标记对长筒石蒜3个居群的遗传多样性及分化程度进行了研究。12条随机引物扩增出94个可分析位点,多态位点比率(PPB)为65.96%,表明长筒石蒜具有比较高的遗传多样性。经POP-GENE32分析表明:Nei’s基因多样性指数(h)为0.1897,香农多样性指数(Ⅰ)为0.2945,基因分化系数(GST)为0.1191,基因流(Nm)为3.6980。经WINAMOVA分析表明:居群内遗传变异占71.75%,而居群间只占28.25%。遗传多样性分析表明,各居群的遗传多样性水平由高到低为琅琊山居群>宝华山居群>盱眙居群。遗传分化表明:长筒石蒜各居群间遗传分化程度较低;大部分遗传变异存在于居群内部,表明其具有较强的进化潜力,自然情况下不会处于濒危状态,野生种质资源的破坏,主要来自于人为干扰。     

濒危植物毛瓣金花茶遗传多样性的ISSR分析

采用ISSR分子标记对毛瓣金花茶6个自然居群的遗传多样性进行了分析。利用11个引物对150个个体进行了扩增,共扩增出92条条带,其中多态性条带74条。毛瓣金花茶在物种水平和居群水平都表现出相对较高的遗传多样性,在物种水平上,多态位点百分率(PPB)为80.43%,Nei’s基因多样性指数(h)为0.245 1,Shannon多样性指数(I)为0.377 6;在居群水平上,PPB为58.70%~66.30%,h为0.199 7~0.229 3,I为0.300 9~0.343 8。Nei’s遗传多样性分析和AMOVA分析表明,毛瓣金花茶的遗传变异主要存在于居群内,居群间的遗传分化程度较低(Gst=0.126 6,Φst=11.37%),基因流(Nm)为3.448 0。Mantel检测表明,居群间的遗传距离和地理距离之间存在显著的相关关系(r=0.755 1,P0.05)。研究认为,毛瓣金花茶较高的遗传多样性和较低的遗传分化可能与其异交型繁育系统和鸟类传粉有关。     

刚毛柽柳天然居群遗传多样性初探

柽柳是荒漠地区主要的灌木资源树种。以刚毛柽柳为代表,运用RAPD技术分析了广布于新疆境内9个刚毛柽柳(Tamarix hispida L．)天然居群的遗传多样性及居群间的遗传分化。10条随机引物检测到157个可重复的位点,其中多态位点155个,占总位点数的98．7％。由Shannon表型多样性指数和Nei基因多样性指数估计居群间遗传分化百分比分别为62．5％和55．30％,表明刚毛柽柳种内的遗传变异主要存在于居群间。根据以上结果,我们认为新疆境内刚毛柽柳天然居群的遗传多样性很丰富,居群间分化程度较高;繁育系统属于一种自交和不完全异交混合的交配类型;形成并维持其分布格局的主要因素是基因流的隔离。     

基于RAPD标记的皖南山核桃野生居群遗传多样性分析

应用随机扩增多态性DNA(RAPD)分子标记方法分析了皖南山区4个山核桃(Carya cathayensis)野生居群的遗传多样性及其分化程度。由POPGENE软件分析表明,15条随机引物共检测出139个扩增条带,其中多态性条带87个,多态性位点百分比(PPB)为62.59%,各居群平均多态性位点百分比(PPB)为43.35%。物种水平Shannon信息多样性指数(I)为0.208,Nei基因多样性指数(H)为0.124,多样性水平较低。由于受到地理隔离的影响,居群间的基因流较低(Nm=0.700),遗传分化程度相对较高(Gst=0.417)。     

莲瓣兰DALP遗传多样性研究

采用DALP(Direct amplification of length polymorphism)检测莲瓣兰5个居群的遗传结构.5个引物组合共检测到103个多态位点.和其它具有相似生活史(多年生草本、以动物为媒介的杂交、种子随风散布)的物种相比,莲瓣兰原变种水平(PPB=88.18％,A=1.8818,Ae=1.4880,H=0.2911,I=0.4412)和物种水平(PPB=93.64％,A=1.9364,Ae=1.5262,H=0.3129,I=0.4732)均具有较高的遗传多样性;各居群间(Gst=0.3292)存在较大的遗传分化.基因流的估计值(Nm=1.0186)表明莲瓣兰物种水平上各居群间每代有1.0186个移居个体.地理隔离和选择压力可能是造成莲瓣兰居群间基因流动受到限制的原因.在这些研究的基础上,探讨了野生莲瓣兰资源的保护问题.     

药用植物天麻（Gastrodia elata Bl.）的等位酶遗传变异及其变型间的遗传关系

采用超薄平板聚丙烯酰胺等电聚焦电泳,对湖北西部药用植物天麻（Gastrodia elata Bl.）的4种变型进行了等位酶遗传变异的初步分析。在6个酶系统共检测到17个清晰位点和37个等位基因,其中多态位点11个,位点最大等位基因数为4,位点Acp-4和Prx-2的等位基因表现出变型特异性。遗传多样性分析结果表明：天麻在物种水平维持着较高遗传多样性,平均多态位点比率P=56.3%,每位点平均等位基因数A=2.1,平均预期杂合度He=0.222;但其变型水平遗传多样性较低（P=42.2%,A=1.7,He=0.146）,其中乌天麻遗传多样性最高,药天麻最低。天麻变型间遗传分化系数（GST）达0.3595,平均基因流（Nm）仅为0.4450,说明天麻变型间遗传分化较大,缺乏基因交流。聚类分析结果表明,天麻居群以变型为单元优先聚类而非地域优先聚类,揭示各天麻变型在遗传上是相对独立的进化显著单元,支持天麻种内变型的划分。红天麻与乌天麻两变型最为近缘,火天麻与药天麻两类群有着较近的遗传关系。     

岛屿植物舟山新木姜子居群遗传多样性的RAPD分析

基于随机扩增多态 DNA(RAPD)方法分析了舟山群岛濒危植物舟山新木姜子 (N eolitsea sericea) 6个居群的遗传多样性及分化程度。 10条随机引物扩增出 84个可分析位点 ,多态位点百分比 (PPL)为 3 8.10 %。经 POPOGENE分析发现 ,舟山新木姜子居群平均水平的多态位点百分比 (PPL )为 2 3 .18% ,Nei' s基因多样度 (HE)为 0 .0 793 ,Shannon信息指数 (H )为 0 .12 0 1,与其它岛屿植物比较具有中等偏低水平的遗传多样性 ;岛屿各居群间遗传分化程度较高 (Gst=0 .3 646) ;地理距离与遗传距离之间具有显著相关性 (r=0 .7697,P=96.62 % ) ,岛屿隔离效应是导致居群间遗传分化的重要因素。结合居群遗传多样性及UPGMA聚类分析 ,推测普陀山岛舟山新木姜子部分个体可能为大猫岛迁入的后裔 ,而朱家尖岛舟山新木姜子则由人为移植自普陀山岛。基于舟山新木姜子的物种保护及资源利用 ,建议加强现有自然居群的就地保护 ,促进居群自然更新 ;建立种质资源库 ,收集不同岛屿的种源进行混合繁殖 ,促进基因交流 ;选育优良品系用于海岛植被恢复及园林观赏     

Mixing source populations increases genetic diversity of restored rare plant populations

The genetic diversity of germplasm used in reintroduction and restoration efforts can influence how resulting populations establish, reproduce, and evolve over time, particularly in disturbed and changing conditions. Regional admixture provenancing, mixing seeds derived from multiple populations within the same region as the target site, has been suggested to produce genetically diverse germplasm. Yet little empirical evidence shows how genetic diversity in germplasm resulting from this approach compares to source populations, or how it varies in restored populations. Here, we use neutral molecular markers to follow genetic diversity through production and use of germplasm when mixing multiple source populations in nursery production beds. Castilleja levisecta is a rare species experiencing inbreeding depression in remaining populations, with a federal recovery plan requiring the re‐establishment of populations in areas where it has been extirpated. Specifically, we track diversity from wild‐collected source populations through different production approaches and reintroductions using two propagule types. We show that measures of genetic diversity, inbreeding, and relatedness change during the production and use of material produced with a regional admixture provenancing approach, with the step at which source populations are mixed and germplasm type used influencing whether all source populations are equally represented. While genetic diversity increased throughout the process, inbreeding and relatedness increased in nursery production beds but decreased in reintroductions, with the lowest inbreeding and relatedness in populations restored using seeds rather than plugs. The results highlight the importance of taking an integrated approach informed by research when planning and implementing reintroductions with mixed‐source germplasm.     

Variable populations within variable populations: quantifying mitochondrial heteroplasmy in natural populations of the gynodioecious plant Silene vulgaris

Populations of mitochondria reside within individuals. Among angiosperms, these populations are rarely considered as genetically variable entities and typically are not found to be heteroplasmic in nature, leading to the widespread assumption that plant mitochondrial populations are homoplasmic. However, empirical studies of mitochondrial variation in angiosperms are relatively uncommon due to a paucity of sequence variation. Recent greenhouse studies of Silene vulgaris suggested that heteroplasmy might occur in this species at a level that it is biologically relevant. Here, we use established qualitative methods and a novel quantitative PCR method to study the intraindividual population genetics of mitochondria across two generations in natural populations of S. vulgaris. We show incidences of heteroplasmy for mitochondrial atpA and patterns of inheritance that are suggestive of more widespread heteroplasmy at both atpA and cox1. Further, our results demonstrate that quantitative levels of mitochondrial variation within individuals are high, constituting 26% of the total in one population. These findings are most consistent with a biparental model of mitochondrial inheritance. However, selection within individuals may be instrumental in the maintenance of variation because S. vulgaris is gynodioecious. Male sterility is, in part, regulated by the mitochondrial genome, and strong selection pressures appear to influence the frequency of females in these populations.     

Studies of wireworm populations

A method has been developed, and is here briefly described, by means of which all the wireworm larvae of all stages can be collected from soil samples. By use of that method, complete wireworm populations have been obtained from soil samples of three types, two of which provide large homogeneous populations for detailed study while the third gives information about the seasonal and spatial infestation of fields. These collections show that the wireworm population of English pasture land is on the average about three times as large as has been commonly supposed. Populations have been found ranging up to ten millions per acre in the top 12 in. of soil. In two pastures studied intensively throughout the year, the wireworm population has been found to consist of large numbers of small larvae, decreasing numbers of larger larvae, and comparatively few of the very large larvae that have usually been allowed to represent the population. Such a composition is shown to be characteristic of wireworm populations under old grass at all seasons of the year and in several fields in different parts of the country. This result suggests that in research on the wireworm problem it is desirable to take into consideration the whole wireworm population throughout the year, not merely the large larvae during the cropping season.     

Dynamics of human populations

This study expands on earlier findings of racial/ethnic and education–allostatic load associations by assessing whether racial/ethnic differences in allostatic load persist across all levels of educational attainment. This study used data from four recent waves of the National Health and Nutrition Survey (NHANES). Results from this study suggest that allostatic load differs significantly by race/ethnicity and educational attainment overall, but that the race/ethnicity association is not consistent across education level. Analysis of interactions and education-stratified models suggest that allostatic load levels do not differ by race/ethnicity for individuals with low education; rather, the largest allostatic load differentials for Mexican Americans (p < .01) and non-Hispanic blacks (p < .001) are observed for individuals with a college degree or more. These findings add to the growing evidence that differences in socioeconomic opportunities by race/ethnicity are likely a consequence of differential returns to education, which contribute to higher stress burdens among minorities compared to non-Hispanic whites.