Phylogenetic relationships of host insects of Cordyceps sinensis inferred from mitochondrial Cytochrome b sequences

This study used the sequence of the mitochondrial Cytochrome b (Cytb) to estimate phylogenetic relationships among host Hepialidae insects of Cordyceps sinensis. Genome DNA of host insect was extracted from the dead larva head part of 18 cordyceps populations and 2 species of Hepialus, and the Cytb fragment of host insect was amplified with PCR technique. The nucleotide sequence alignments and their homologous sequences of 24 species host Hepialidae insects of Cordyceps sinensis were obtained from GenBank and were used to construct phylogenetic trees based on neighbor-joining method. The results showed that genus Bipectilus diverged earlier than genus Hepialus and Hepialiscus. Hepialus host insects of Cordyceps sinensis have multitudinous species with different morphological characteristics and geographical distributions. The interspecific genetic differentiations are obvious in Hepialus. Thus, the genus Hepialus might be considered as polyphyletic origin. Cytb sequences have abundant variations among the host insects of Cordyceps sinensis on specific and generic level. The divergence rate of Cytb sequences among the species in Hepialus ranged from 0.23% to 9.24%, except that Hepialus pratensis and Hepialus jinshaensis have the same sequence. Cytb sequence can be used for species identification of host insects of Cordyceps sinensis, but further confirmation in more host insect species is needed. To obtain the Cytb sequence of host insect by amplifying DNA extracted from the head part of dead larva in cordyceps turns out to be an effective and accurate approach, which will be useful for studies on phylogeny and genetic structure of host insects of cordyceps populations, especially for analyzing relationships between C. sinensis and its host insects.     

Phylogenetic relationships of host insects of Cordyceps sinensis inferred from mitochondrial Cytochrome b sequences

This study used the sequence of the mitochondrial Cytochrome b(Cytb)to estimate phylogenetic relationships among host Hepialidae insects of Cordyceps sinensis.Genome DNA of host insect was extracted from the dead larva head part of 18 cordyceps populations and 2 species of Hepialus,and the Cytb fragment of host insect was amplified with PCR technique.The nucleotide sequence alignments and their homologous sequences of 24 species host Hepialidae insects of Cordyceps sinensis were obtained from GenBank and were used to construct phylogenetic trees based on neighbor-joining method.The results showed that genus Bipectilus diverged earlier than genus Hepialus and Hepialiscus.Hepialus host insects of Cordyceps sinensis have multitudinous species with different morphological characteristics and geographical distributions.The interspecific genetic differentiations are obvious in Hepialus.Thus,the genus Hepialus might be considered as polyphyletic origin.Cytb sequences have abundant variations among the host insects of Cordyceps sinensis on spe- cific and generic level.The divergence rate of Cytb sequences among the species in Hepialus ranged from 0.23% to 9.24%,except that Hepialus pratensis and Hepialus jinshaensis have the same sequence.Cytb sequence can be used for species identification of host insects of Cordyceps sinensis,but further confirmation in more host insect species is needed.To obtain the Cytb sequence of host insect by ampli- fying DNA extracted from the head part of dead larva in cordyceps turns out to be an effective and accurate approach,which will be useful for studies on phylogeny and genetic structure of host insects of cordyceps populations,especially for analyzing relationships between C. sinensis and its host insects.     

Accelerated evolution of a false-truffle from a mushroom ancestor

THE false-truffles (Hymenogastrales) are a group of basidomycetous fungi that produce underground truffle-like basidiocarps. They are generally believed to be independently derived from several mushroom lineages, but extensive morphological divergence often obscures recognition of these phylogenetic connections. Comparisons of mitochondrial DNA now demonstrate a surprisingly close relationship between species of false-truffles in the genus Rhizopogon (Hymenogastraceae) and the mushroom genus Suillus (Boletaceae). The striking morphological differences separating all Suillus species from Rhizopogon imply an acceleration in the rate of morphological change relative to molecular change during the evolution of these false-truffles from their mushroom ancestors. This acceleration can best be explained by rapid morphological divergence resulting from selective pressures which may have acted on a small number of developmental genes.     

Conservation of polymorphic simple sequence loci in cetacean species

Length polymorphisms within simple-sequence loci occur ubiquitously in non-coding eukaryotic DNA and can be highly informative in the analysis of natural populations. Simple-sequence length polymorphisms (SSLP) in the long-finned pilot whale Globicephala melas (Delphinidae) have provided useful information on the mating system as well as on the genetic structure of populations. We have therefore tested whether the polymerase chain reaction primers designed for Globicephala could also be used to uncover variability in other whale species. Homologous loci could indeed be amplified from a diverse range of whales, including all toothed (Odontoceti) and baleen whales (Mysticeti) tested. Cloning and sequencing these loci from 11 different species revealed an unusually high conservation of sequences flanking the simple-sequence stretches, averaging 3.2% difference over 35-40 Myr. This represents the lowest divergence rate for neutral nucleotide positions found for any species group so far and raises the possible need for a re-evaluation of the age of the modern whales. On the other hand, the high conservation of non-coding sequences in whales simplifies the application of SSLP DNA fingerprinting in cetacean species, as primers designed for one species will often uncover variability in other species.     

Phylogenetic positions of some genera and species of the family Buccinidae (Gastropoda: Mollusca) from China based on ribosomal RNA and COI sequences

A phylogenetic analysis of members of the family Buccinidae was conducted using 18S rRNA gene, 28S rRNA gene and the mitochondrial cytochrome oxidase Ⅰ gene. We studied 18 species of Buccinidae that belong to eight different genera and inhabit the China coastal seas. We analyzed the patterns of divergence between an outgroup and basal ingroup taxa, the monophyly of the genus Neptunea, and the position of one unnamed species within the Buccinidae. A phylogenetic tree (neighbor-joining (NJ) method) was reconstructed based on the sequences of 18S rRNA, 28S rRNA and COI, with Rapana venosa as outgroup. The NJ tree indicated that the 18 species could be divided into five groups. The genus Buccinum was monophyletic, whereas Neptunea was shown to be paraphyletic since it included Siphonalia subdilatata and Neptunea sp., a new species. This novel species otherwise clustered consistently with Neptunea cumingi in three other phylogenetic trees, showing a low genetic distance and divergence percentage of sequences belonging to the genus Neptunea. A smaller genetic distance and a smaller difference of 18S rRNA, 28S rRNA and COI sequences between Neptunea cumingii and Neptunea arthritica cumingii confirmed them to be the same species.     

典型喀斯特区域植物物种多样性研究——以广西中越边境喀斯特地区种子植物为例

【目的】广西中越边境地区喀斯特地貌广泛发育,是广西生物多样性研究和保护的关键区域,也是全球生物多样性研究和保护的热点地区。鉴于当前该地区植物区系复杂,植物调查薄弱,生物多样性面临严重威胁,特选该区域开展研究。【方法】基于相关文献资料,整合野外调查数据和历史标本信息,完成该地区的种子植物物种多样性编目,并据此开展综合分析。【结果】广西中越边境喀斯特地区共有种子植物3 118种(含种下单位),隶属于187科、1 050属,科属以寡种占优势,但优势科属也较明显。该区野生种子植物184科,可分为10个分布区类型,其中热带性质的共97科,温带性质的共39科,种子植物热带性科和温带性科的比值约为2.5/1,在属级水平上,该区野生的1 028属可划分为14个分布区类型和24个变型,热带性属共736个,温带性属共219个,热带性属和温带性属的比值约为3.4/1。可见不管在科级还是属级水平都表明该地区地理成分复杂,表现出强烈的热带性质。广西中越边境喀斯特地区种子植物特有现象突出,该地区拥有294种广西特有植物;还有351种为石灰岩特有植物,占该地区总种数的11.51%,另外还有423种为石灰岩适宜植物,综合二者,广西中越边境喀斯特地区典型的喜钙植物种类高达774种,占该地区总种数的25.38%,而且这些特有植物集中于少数的几个科属内,科属优势明显。广西中越边境喀斯特地区珍稀濒危植物众多,其中国家重点保护野生植物29种,包括11种Ⅰ级和18种Ⅱ级保护植物;广西重点保护野生植物有292种,兰科植物就多达261种,其余的31种;另外还有12种被列为全国极小种群保护野生植物。【结论】广西中越边境喀斯特地区植物物种多样性丰富,地理成分复杂,表现出明显的热带性质,特有现象突出,珍稀濒危植物众多,该地区具有重要的研究和保护价值,对广西乃至中国的生物多样性研究和保护都有着举足轻重的意义。     

秦皇岛市农田杂草的种类与生育期

实地考察了秦皇岛市下辖的三区四县 (北戴河区、山海关区、海港区、昌黎县、抚宁县、卢龙县、青龙县 )农田杂草的种类、分布、危害及主要杂草的生育期。秦皇岛市有农田杂草 5 3科 15 8属 2 4 4种 ,其中恶性杂草 6科 11属 12种 ;寄生性杂草 1科 1属 4种 ;普通性杂草 4 6科 14 1属 2 2 8种。列出了秦皇岛市农田杂草名录。     

长尾线虫属分类研究进展

长尾线虫属(Seinura spp.)是一类能捕食其他线虫的捕食性线虫,具有维持土壤线虫种群生态平衡的作用。此外,长尾属线虫还是被用于基础生物学研究的生物材料。笔者综述了长尾线虫属的形态分类特征及其43个有效种的主要区别特征,为长尾属线虫的研究提供分类学依据。     

Speciation in a ring

The evolutionary divergence of a single species into two has never been directly observed in nature, primarily because speciation can take a long time to occur. A ring species, in which a chain of intergrading populations encircles a barrier and the terminal forms coexist without interbreeding, provides a situation in which variation in space can be used to infer variation in time. Here we reconstruct the pathway to speciation between two reproductively isolated forms of greenish warbler (Phylloscopus trochiloides). These two taxa do not interbreed in central Siberia but are connected by a long chain of intergrading populations encircling the Tibetan Plateau to the south. Molecular data and climatic history imply that the reproductively isolated taxa came into contact following expansions northward around the western and eastern sides of the plateau. Parallel selection pressures for increased song complexity during the northward expansions have been accompanied by divergence in song structure. Playback experiments show that the two Siberian forms do not recognize each other's songs. Our results show how gradual divergence in a trait involved in mate choice leads to the formation of new species.     

安徽蓼属(Polygonum L.)植物的研究

蓼属(Polygonum L.)为本省蓼科植物中种类最多的一属。作者就其形态特征、系统分类、生态地理分布、区系特点及资源利用等方面进行了研究;现记载安徽蓼属植物共42种(包括变种),其中5种1变种为本省分布新记录,属下分为7组,各组在水平分布与垂直分布方面显示一定规律性;区系分析表明安徽蓼属80％的种为北温带类型,与邻省及邻国日本关系密切,与我国其他地区也有一定程度的联系,区系组成反映本省处于南北植物交汇的过渡地带特点。     

Genetic evidence for complex speciation of humans and chimpanzees

The genetic divergence time between two species varies substantially across the genome, conveying important information about the timing and process of speciation. Here we develop a framework for studying this variation and apply it to about 20 million base pairs of aligned sequence from humans, chimpanzees, gorillas and more distantly related primates. Human-chimpanzee genetic divergence varies from less than 84% to more than 147% of the average, a range of more than 4 million years. Our analysis also shows that human-chimpanzee speciation occurred less than 6.3 million years ago and probably more recently, conflicting with some interpretations of ancient fossils. Most strikingly, chromosome X shows an extremely young genetic divergence time, close to the genome minimum along nearly its entire length. These unexpected features would be explained if the human and chimpanzee lineages initially diverged, then later exchanged genes before separating permanently.     

九种蝗虫核仁组成区定位及其细胞分类学意义

本文以银染技术对我国九种蝗虫(分隶3个科8个属)进行了核仁组成区(Nucleolus-Organizing Region)的观察分析。结果表明:蝗总科昆虫同一属内NOR定位有一基本模式,属内种间具有相对恒定性,无显著差异,而在不同属间则有差别。因此,在揭示属内同源关系,进行近缘属之间的比较和鉴定时,NOR定位具有重要意义,并与其它各种染色体带型方法一起,构成细胞分类学的一个重要手段。     

Theory predicts the uneven distribution of genetic diversity within species

Global efforts to conserve species have been strongly influenced by the heterogeneous distribution of species diversity across the Earth. This is manifest in conservation efforts focused on diversity hotspots. The conservation of genetic diversity within an individual species is an important factor in its survival in the face of environmental changes and disease. Here we show that diversity within species is also distributed unevenly. Using simple genealogical models, we show that genetic distinctiveness has a scale-free power law distribution. This property implies that a disproportionate fraction of the diversity is concentrated in small sub-populations, even when the population is well-mixed. Small groups are of such importance to overall population diversity that even without extrinsic perturbations, there are large fluctuations in diversity owing to extinctions of these small groups. We also show that diversity can be geographically non-uniform--potentially including sharp boundaries between distantly related organisms--without extrinsic causes such as barriers to gene flow or past migration events. We obtained these results by studying the fundamental scaling properties of genealogical trees. Our theoretical results agree with field data from global samples of Pseudomonas bacteria. Contrary to previous studies, our results imply that diversity loss owing to severe extinction events is high, and focusing conservation efforts on highly distinctive groups can save much of the diversity.     

Repeated morphological evolution through cis-regulatory changes in a pleiotropic gene

The independent evolution of morphological similarities is widespread. For simple traits, such as overall body colour, repeated transitions by means of mutations in the same gene may be common. However, for more complex traits, the possible genetic paths may be more numerous; the molecular mechanisms underlying their independent origins and the extent to which they are constrained to follow certain genetic paths are largely unknown. Here we show that a male wing pigmentation pattern involved in courtship display has been gained and lost multiple times in a Drosophila clade. Each of the cases we have analysed (two gains and two losses) involved regulatory changes at the pleiotropic pigmentation gene yellow. Losses involved the parallel inactivation of the same cis-regulatory element (CRE), with changes at a few nucleotides sufficient to account for the functional divergence of one element between two sibling species. Surprisingly, two independent gains of wing spots resulted from the co-option of distinct ancestral CREs. These results demonstrate how the functional diversification of the modular CREs of pleiotropic genes contributes to evolutionary novelty and the independent evolution of morphological similarities.     

赤点石斑鱼群体遗传结构的微卫星分析

 赤点石斑鱼Epinephelus akaara作为我国南方海域的经济水产鱼类,已面临着种质资源匮乏,过度开发的局面。为了开展其保护生物学研究和促进养殖业的健康发展,开展了赤点石斑鱼群体的微卫星分析,对中国东南沿海7个赤点石斑鱼群体的遗传变异进行了研究,发现在不同渔场之间的种群存在着丰富的遗传多样性,并且具有明显的地理区域分布特征,这为赤点石斑鱼的种质资源研究和遗传育种提供了遗传学基础。     

Asian origin for Polystichum （Dryopteridaceae） based on rbcL sequences

Chloroplast rbcL sequences of 60 species of Polystichum sensu lato (s.l.), including 23 new sequences from southwest China, were used to assess the phylogenetic relationships within the genus. On the basis of estimated evolution rate of rbcL gene and the genetic distance data that passed relative-rate tests, we further estimated the divergence times between some clades of the genus. The phylogenetic relationships were inferred using the neighbor-joining and maximum-parsimony methods, both methods producing trees with completely congruent topology. These trees reveal that all species of Polystichum s.l. in this study (including Cyrtomium and Cyrtomidictyum) form a monophyletic group. The basal split in Polystichum s.l. separates a clade with all Asian members from a clade containing other species from all over the world. The phylogenetic and divergence time estimation results lead us to suggest that Polystichum s.l. originated in Asia in the late Late Cretacous (≈76 Ma) and migrated into other places in the world in early Eocene(≈46 Ma).     

The cost of inbreeding in Arabidopsis

Population geneticists have long sought to estimate the distribution of selection intensities among genes of diverse function across the genome. Only recently have DNA sequencing and analytical techniques converged to make this possible. Important advances have come from comparing genetic variation within species (polymorphism) with fixed differences between species (divergence). These approaches have been used to examine individual genes for evidence of selection. Here we use the fact that the time since species divergence allows combination of data across genes. In a comparison of amino-acid replacements among species of the mustard weed Arabidopsis with those among species of the fruitfly Drosophila, we find evidence for predominantly beneficial gene substitutions in Drosophila but predominantly detrimental substitutions in Arabidopsis. We attribute this difference to the Arabidopsis mating system of partial self-fertilization, which corroborates a prediction of population genetics theory that species with a high frequency of inbreeding are less efficient in eliminating deleterious mutations owing to their reduced effective population size.     

树蕨类化石在淮北煤田的发现及意义

淮北煤田早二叠世晚期下石盒子组树蕨类茎干印痕化石丰富，计有４０余块。分属于蹄痕茎属（Ｃａｕｌｏｐｔｅｒｉｓ）、大痕木属（Ｍｅｇａｐｈｙｔｏｎ）及皱痕茎属（ＰｔｙｃｈｏＰｔｅｒｉｓ），共３属９种；其中蹄痕茎属４种（包括２个新种，Ｃａｕｌｏｐｔｒｉｓｙａｎｇｚｈｕａｎｇｅｎｓｉｓｓｐ．ｎｏｖ．和Ｃａｕｌｏｐｔｅｒｉｓｐｓｉｌｏｃｉｃａｔｒｉｘｓｐ．ｎｏｖ．）；大痕木属在国内尚属首次报道，仅见１种；皱痕茎属在国内亦属首次发现，鉴定有４个未定种。该类化石在本区以极大的丰度和良好的保存为特征，其发育显示该区早二叠世晚期热带雨林气候盛行。其次，说明树蕨类在其晚期发育中心已由欧美区移至华夏区。此外，该类在本区的发育是华夏植物地理区分化渐趋强烈的直接证据。     

Wormy mice in a hybrid zone

As one approach to analysing the genetic barriers between species, we studied the numbers and types of parasitic worms in two species of house mice (Mus musculus and M. domesticus) and in their natural hybrids. Where the ranges of these two species meet in southern Germany, there is a zone of hybridization less than 20 kilometres across, in which about 98% of the mice have backcross genotypes. Fourteen of the 46 mice tested from within the zone have over 500 pinworms per gut, a number far exceeding the mean of 40 per gut for other mice inside and outside the zone. Other nematodes have a similar, non-random distribution. The number of mice bearing 9 or more tapeworms per gut is also excessive in the hybrid zone. These extraordinarily wormy mice may be unusually susceptible to parasitism; the different species may have different genes for resistance, and recombinant backcross animals may lose both. Our findings support the view that the hybrid populations may have reduced fitness and thereby act as a genetic sink, interfering with the flow of genes between the two species. The possibility that environmental or ecological peculiarites in the zone of hybridization make the mice more liable to infection is not supported.