Isolation and characterization of 11 polymerase chain reaction primers for microsatellite loci for the Chilean marine isopod Excirolana hirsuticauda

The Chilean isopod Excirolana hirsuticauda is a marine benthic brooder with wide distributional range and low potential for long-distance dispersal. Eleven microsatellite markers were developed for E. hirsuticauda using enriched libraries. Characterization of those loci in 35 individuals from Playa Blanca beach showed high allelic diversity with a mean of 10.9 alleles per locus. The average expected and observed heterozygosities were 0.65 and 0.41. These microsatellite loci are the first published for any Excirolana species and should be useful to study the genetic structure of E. hirsuticauda.     

两种盐生植物内生真菌多样性及其功能预测

【背景】植物内生菌是微生物群落中一类非常重要的组成部分,是重要的微生物资源库,在植物促生、抗逆等多个领域有重要的研究和应用价值。【目的】进一步了解干旱荒漠区盐生植物内生真菌的多样性、群落结构和潜在功能特征。【方法】对生长在乌兹别克斯坦西咸海岸边的两种盐生植物毛足假木贼(Anabasis eriopoda abbreviated as AE)和展枝假木贼(A. truncata abbreviated as AT)的内生真菌群落进行扩增子测序分析。【结果】共获得166个ampliconsequencingvariants(ASVs),涉及4门49属,其中Neocamarosporium、Botryosphaeria和Alternaria及其所属高级分类单元是优势类群。多样性和群落组成分析显示两种盐生植物的内生真菌存在较为明显的差异,并包含一些潜在的新分类单元。基于PICRUSt2和FUNGuild的功能预测结果表明这两种盐生植物内生真菌的潜在功能和营养方式多样且表现出宿主差异性。【结论】盐生植物内生真菌具有较高的多样性和潜在的资源价值,有待进一步挖掘和研究。     

城市景观格局对大蚰蜒种群遗传结构的影响

城市化改变了原有的自然景观格局, 导致生物多样性丧失。土壤动物在食物链中扮演着关键角色, 对维持生态系统稳定起着重要作用。研究城市景观格局变化对土壤动物遗传多样性和种群结构的影响, 可以为维持城市生态系统稳定及其生物多样性保护提供理论依据。本研究采集了南京地区7个种群共133个大蚰蜒(Thereuopoda clunifera)样品, 以线粒体Cytb基因和6个微卫星位点为分子标记, 分析了大蚰蜒的种群遗传结构及其影响因素。结果显示: 7个种群中共检测出6个Cytb单倍型和14个突变位点, 各种群核苷酸多样性指数均低于0.005, 遗传多样性处在较低水平。而微卫星标记反映各种群的平均等位基因数在4.167-5.167之间, 观测杂合度在0.470-0.603之间, 各种群微卫星多样性较高。栖息地面积和周边城市化程度与种群遗传多样性间不存在相关性。种群间两两遗传分化系数介于0.020-0.106, 基因流介于2.108-12.266, 表明种群间遗传分化水平较低, 存在较为频繁的基因交流。遗传分化水平与预测的地理阻力呈显著正相关, 大蚰蜒的种群遗传结构可能受到城市化的影响。斑块间良好的连通性保证了种群间的基因流, 散布的城市绿地可作为廊道, 为大蚰蜒提供扩散机会。本研究结果可为城市土壤动物多样性的保护提供理论依据。     

Isolation of microsatellites from Girella tricuspidata

Microsatellites were isolated from Girella tricuspidata (Girellidae) and screened for 64 individuals collected from coastal reefs in New South Wales, Australia. All seven loci tested were highly polymorphic, having seven to 42 alleles with average heterozygosities between 0.44 and 1.0. One locus (GT1N8) had a significant excess of homozygotes, probably due to the presence of null alleles. These microsatellite loci should be informative for examining population genetics of this species.     

Genetic differentiation and diversity of Acacia koa populations in the Hawaiian Islands

Acacia koa A. Gray (koa) is a leguminous tree endemic to the Hawaiian Islands and can be divided into morphologically distinguishable groups of A. koaia Hillebrand, A. koa and populations that are intermediate between these extremes. The objectives of this investigation were to distinguish among divergent groups of koa at molecular levels, and to determine genetic diversity within and among the groups. Phylogenetic analyses using the ITS/5.8S rDNA and trnK intron sequences did not separate the representative koa types into distinct clusters. An unweighted pair group method with arithmetic mean cluster analysis and principal coordinate analysis, based on allele profiles of 12 microsatellite loci for 215 individual koa samples, separated the population into three distinct clusters consistent with their morphology, A. koaia, A. koa and intermediate forms. There was an average of 8.8 alleles per polymorphic locus (AP) among all koa and koaia individuals. The intermediate populations had the highest genetic diversity (H′ = 1.599), AP (7.9) and total number of unique alleles (21), whereas A. koaia and A. koa showed similar levels of genetic diversity (H′ = 0.965 and 0.943, respectively). No correlation was observed between geographic distance and genetic distance as determined by a Mantel test (r = 0.027, P = 0.91). The data presented here support previous recommendations that morphological variation within koa should be recognized at the subspecific level rather than as distinct species.     

Isolation and characterization of microsatellite markers for Acacia senegal (L.) Willd., a multipurpose arid and semi-arid tree

Acacia senegal is a multipurpose African tree that improves the soil fertility of degraded areas. The species is exploited mainly for gum arabic, but it also supplies fuel wood and fodder for animals. Despite its wide distribution in Africa, no microsatellite markers have yet been characterized for this species. In this study, we characterized 11 polymorphic microsatellite loci specifically designed for A. senegal and analysed 247 individuals from three populations from Niger. On average, 10.9 alleles per locus were detected and expected heterozygosity ranged from 0.160 to 0.794, showing the ability of the markers to detect genetic diversity in this species.     

Implications of isolation and low genetic diversity in peripheral populations of an amphi-Atlantic coral

Limited dispersal and connectivity in marine organisms can have negative fitness effects in populations that are small and isolated, but reduced genetic exchange may also promote the potential for local adaptation. Here, we compare the levels of genetic diversity and connectivity in the coral Montastraea cavernosa among both central and peripheral populations throughout its range in the Atlantic. Genetic data from one mitochondrial and two nuclear loci in 191 individuals show that M. cavernosa is subdivided into three genetically distinct regions in the Atlantic: Caribbean-North Atlantic, Western South Atlantic (Brazil) and Eastern Tropical Atlantic (West Africa). Within each region, populations have similar allele frequencies and levels of genetic diversity; indeed, no significant differentiation was found between populations separated by as much as 3000 km, suggesting that this coral species has the ability to disperse over large distances. Gene flow within regions does not, however, translate into connectivity across the entire Atlantic. Instead, substantial differences in allele frequencies across regions suggest that genetic exchange is infrequent between the Caribbean, Brazil and West Africa. Furthermore, markedly lower levels of genetic diversity are observed in the Brazilian and West African populations. Genetic diversity and connectivity may contribute to the resilience of a coral population to disturbance. Isolated peripheral populations may be more vulnerable to human impacts, disease or climate change relative to those in the genetically diverse Caribbean-North Atlantic region.     

Phenotypic and genotypic characteristics of Acacia senegal (L.) Willd. root-nodulating bacteria isolated from soils in the dryland part of Senegal

Aims:  We characterized phenotypically and genotypically root-nodulating bacteria associated with Acacia senegal (L.) Willd. isolated from the soils surrounding A. senegal trees in the dry land area of Senegal.
Methods and Results:  The phenotypical and genotypical characterizations we carried out showed a high diversity of A. senegal root-nodulating bacteria. Phenotypic patterns showed adaptations of the rhizobial strains to many environmental stresses such as heat, drought, and salinity. Twelve molecular groups were distinguished by profiles obtained using polymerase chain reaction/restriction fragment length polymorphism techniques from intergenic spacer region rDNA. The highest genetic diversity was found around the A. senegal rhizosphere. Therefore, A. senegal seemed to have a positive influence on occurrence and genotypical diversity of rhizobial populations. Rhizobial isolates obtained in this study belonged phylogenetically to the genera Mesorhizobium and Rhizobium .
Conclusions:  Our results provided information about the genetic diversity of the rhizobial strains associated with A. senegal and suggested the adaptability of natural rhizobial populations to major ecological environmental stress within these soil environments.
Significance and Impact of the Study:  These results suggested a potential selection of compatible and well adapted strains under stress conditions as inoculants for successful A. senegal growth in arid lands.     

Newly developed PCR primers for polymorphic microsatellite loci from the marine isopod Limnoria sp.

Nine microsatellite loci are isolated and characterized for the marine isopod Limnoria sp., a model invertebrate species for the study of connectivity of marine brooders with high potential of dispersal through rafting. Analysis of 35 individuals of one population revealed a mean number of alleles of 12.66 and mean expected heterozygosity of 0.83, indicating a high level of variability at most loci. These polymorphic microsatellite loci should be useful to the study of the geographical distribution of the genetic diversity of this species of Limnoria.     

西藏农作物病原真菌的区域分化初探*

在西藏农作物病原真菌调查基础上,综合分析西藏自然环境条件和社会经济条件对病原真菌分布的影响,将西藏病原真菌分布划分为5个区:(1) 喜马拉雅南侧暖热湿润区; (2)藏东温暖半湿润区; (3)藏南温暖半干旱区; (4) 西喜马拉雅温凉干旱区; (5) 藏北羌塘高寒区;