基于毛髓质指数探讨甘肃鼢鼠、高原鼢鼠、秦岭鼢鼠的分类地位

目前甘肃鼢鼠Myospalax cansus、高原鼢鼠 M.baileyi、秦岭鼢鼠M.rufescens的分类地位一直存有争议,多涉及到与中华鼢鼠M.fontanierii的分类关系.本文分别从成体甘肃鼢鼠、高原鼢鼠、秦岭鼢鼠、中华鼢鼠标本的胡须、头部、背部、腹部、前肢取毛样,经清洗和处理后,在倒置显微镜下观察,用目镜测微尺分别测量和计算其5个部位毛发的毛髓质指数.结果表明:甘肃鼢鼠与中华鼢鼠除胡须髓质指数无显著性差异外,其它部位及各部位综合均有显著差异.高原鼢鼠与秦岭鼢鼠除前肢毛髓质指数无显著性差异外,其它部位及各部位综合均有显著差异;与中华鼢鼠除前肢毛髓质指数无显著差异,其它部位及各部位综合均有显著差异.秦岭鼢鼠除与甘肃鼢鼠的腹部及与中华鼢鼠、高原鼢鼠的前肢毛髓质指数无显著差异外,与其它鼢鼠其余部位及各部位综合均有显著性差异.综合考虑,本研究结果支持甘肃鼢鼠、高原鼢鼠、秦岭鼢鼠各自独立为种的观点.     

高原鼢鼠食性的研究

在高寒草甸和高寒灌丛两种栖息地中捕获高原鼢鼠 1 44只 ,将 92只鼢鼠的胃内容物对照已知植物组织的显微结构进行分析 ,以确定其食物组成。研究结果表明 ,虽然两种栖息地之间的植被组成有极大的差异 ,但是高原鼢鼠的食物组成在两种栖息地之间和性别之间均无明显的不同 ,不同植物出现的频次却有明显的差异。禾本科植物在高原鼢鼠的胃内容物中基本没有发现 ,对莎草科植物也只取食两个物种 ,高原鼢鼠所取食的植物主要是杂类草。在两种栖息地中高原鼢鼠喜食度指数最高的 9种植物均为鹅绒委陵菜、直立梗唐松草、丽江风毛菊、雪白委陵菜、美丽风毛菊、细叶亚菊、异叶米口袋、磨岭草和棘豆。     

两种鼢鼠内脏器官形态差异及其分类学意义

分子生物学研究表明,甘肃鼢鼠(Eospalaxcansus)和高原鼢鼠(Eospalax baileyi)是啮齿目(Rodentia),鼹形鼠科(Spalacidae),鼢鼠亚科(Myospalactinae),中华鼢鼠属(Eospalax)的两个     

高原鼢鼠线粒体谱系地理学和遗传多样性

高原鼢鼠是一类地下独居啮齿动物,为青藏高原特有种之一。为研究该物种的谱系地理学和遗传多样性,本文测定了采自青藏高原东部3个地理种群8个小种群共37个个体的线粒体D-loop区序列变异。在长度为627bp的序列中,共发现50个变异位点,定义了26种单倍型。该物种的单倍型多样性（Haplotype diversity,H）较高和核苷酸多样性（Nucleotide diversity,πn）较低。谱系分析得到3个稳定的分支,分别与采集的地理种群相吻合：同一地理种群内单倍型之间遗传差异小,而不同地理来源的单倍型之间存在较大区别。距离隔离分析表明高原鼢鼠的遗传分化与地理距离呈正相关。AMOVA分析同样表明地理种群之间存在显著差异：地理种群间变异占遗传变异的80.45%。高原鼢鼠的这种遗传结构特点可能主要是由于第四纪气候变迁、该物种稳定的地下生活环境和有限的迁移能力造成的。     

甘肃鼢鼠和中华鼢鼠繁殖特性的研究

有关中华鼢鼠(Myospalax fontanieri)繁殖的研究国内已有一些报道(王祖望等,1973,灭鼠和鼠类生物学研究报告,第1集,61—72;郑生武,1980,动物学研究,1(4):465;梁杰荣等,1982,动物学杂志(3):13—16)。有关甘肃鼢鼠(Myospalax cansus)的繁殖尚未见报道。研究种群的繁殖特征对分析种群动态具有重要意义。本文作者于1988年3—10月分别在陕西省延安地区和山西省临汾地区对甘肃鼢鼠和中华鼢鼠的种群繁殖特征进行了研究,现报道如下。     

基于线粒体控制区的序列变异分析青海东部甘肃鼢鼠遗传多样性

甘肃鼢鼠(Myospalax cansus)是一种终年营地下独居生活的小型掘土类动物。本文通过测定mt DNA的控制区部分序列(530 bp)变异,分析青海东部地区8个甘肃鼢鼠地理种群遗传多样性与遗传结构。158个样本共发现26个变异位点,定义了39种单倍型,整体的平均单倍型多样性高(h=0.953 2)、核苷酸多样性低(π=0.006 36)。歧点分布和中性检验均说明青海东部甘肃鼢鼠种群在历史上存在着快速扩张的事件。基于邻接法构建的网络关系图中,单倍型呈星状分布,没有按地理位置形成对应类群。基因流(Nm)数据显示多数地理种群间基因交流贫乏,AMOVA结果显示种群内与种群间遗传变异分别为48.82%和51.18%,遗传分化明显。IBD分析表明,甘肃鼢鼠的遗传分化与地理距离呈正相关,说明距离隔离对甘肃鼢鼠种群分化具有重要作用。甘肃鼢鼠的这种遗传多样性与种群遗传结构特点,可能是地下生活方式靠挖掘迁移带来的较小扩散能力的结果。     

两种缢蛏线粒体基因全序列扩增方法的比较

介绍了应用长PCR技术扩增缢蛏线粒体全序列的两种方法,并进行了比较.一种方法是使用通用引物扩增COI基因和16S基因并测序后,在两基因的两端分别设计两对引物扩增两基因中间的大片段,分别得到了9.7 kb和7.3 kb的扩增产物.另一种方法是在COI基因序列两端设计一对引物,扩增整个线粒体全序列,得到了17.1 kb的扩增产物.两种方法在缢蛏的研究中进行比较后发现,前一种方法在操作实用性和后期测序方面都比后者好.     

绵羊线粒体DNA D-loop区串联重复序列变异研究

对来自69个我国地方绵羊品种和8个国外引入品种共计77个个体线粒体DNA控制区长度为75bp的串联重复序列进行了测序分析。在309个重复序列中检测到28个变异位点,其中7个为具有2个变异体的单现突变,1个为具有3个变异体的单现突变,20个为具有2个变异体的简约位点。由28个变异位点中归纳出63个单倍型,其中单倍型Ⅰ和单倍型Ⅲ具有较高的比例,分别为12．94％和30.42％。研究结果揭示我国地方绵羊可能起源于两个母系祖先。哈萨克羊和阿勒泰羊间以及蒙古羊和乌珠穆沁羊间分别具有较近的亲缘关系且没有明显的遗传分化。藏绵羊、蒙古羊和乌珠穆沁羊相对哈萨克羊和阿勒泰羊而言具有较低的遗传多样性。     

甘肃鼢鼠适应地下生活的消化道形态和结构的季节可塑性

甘肃鼢鼠(Myospalax cansus)是终生营地下生活的小型哺乳动物,为研究其在自然环境中的消化对策和调节,探讨地下鼠消化道的可塑性,测定了不同季节消化道各器官长度、重量及各器官的组织结构。结果显示,甘肃鼢鼠总消化道长度、各消化器官长度和含内容物总重量无显著季节差异。总消化道及各器官的鲜重和干重多在春季最高,含内容物重量于秋季较高。组织结构有显著性季节变化,黏膜层和肌层的厚度及肠道绒毛高度春季最高。结果表明,甘肃鼢鼠主要依靠肠道重量的增加和组织结构的可塑性变化来适应相对稳定的地下生活环境,无需增加消化器官长度满足其能量需求。     

两种鯻科鱼类线粒体16S rRNA基因片段序列分析

利用PCR技术成功扩增了高体革鯻(Scortum barcoo)和厚唇弱棘喇(Hephaestus fuliginosus)的线粒体16S rRNA基因序列.通过序列测定,得到791 bp的基因片段,碱基A、T、G、C平均含量分别为31.4％、21.2％、20.5％和26.9％,序列中的A+T含量明显高于G+C的含量,这与其他鱼类的16S rRNA基因片段研究结果相一致.通过序列分析发现,高体革鯻和厚唇弱棘喇两序列共存在23处碱基变异,其中碱基转换位点20个,碱基颠换位点3个,转换与颠换比率为6.7,没有发现碱基插入与缺失.与从GenBank中查到的3种蜊科鱼类的同源序列比对,邻接法(neighbor-joining)构建亲缘关系树,结果显示,5种蜊科鱼类聚在一起,分为独立的2支,匀蜊和单色匀鯻及花身蜊聚成1支,高体革鯻和厚唇弱棘鯻聚为1支,说明高体革鯻与厚唇弱棘蜊的亲缘关系比较近,而与其他另外3种鯻科鱼类亲缘关系比较远.     

The relevance of morphology for habitat use and locomotion in two species of wall lizards

Understanding if morphological differences between organisms that occupy different environments are associated to differences in functional performance can suggest a functional link between environmental and morphological variation. In this study we examined three components of the ecomorphological paradigm – morphology, locomotor performance and habitat use – using two syntopic wall lizards endemic to the Iberian Peninsula as a case study to establish whether morphological variation is associated with habitat use and determine the potential relevance of locomotor performance for such an association. Differences in habitat use between both lizards matched patterns of morphological variation. Indeed, individuals of Podarcis guadarramae lusitanicus, which are more flattened, used more rocky environments, whereas Podarcis bocagei, which have higher heads, used more vegetation than rocks. These patterns translated into a significant association between morphology and habitat use. Nevertheless, the two species were only differentiated in some of the functional traits quantified, and locomotor performance did not exhibit an association with morphological traits. Our results suggest that the link between morphology and habitat use is mediated by refuge use, rather than locomotor performance, in this system, and advise caution when extrapolating morphology-performance-environment associations across organisms.     

Structure and evolution of teleost mitochondrial control regions

We amplified and sequenced the mitochondrial control region from 23 species representing six families of teleost fish. The length of this segment is highly variable among even closely related species due to the presence of tandemly repeated sequences and large insertions. The position of the repetitive sequences suggests that they arise during replication both near the origin of replication and at the site of termination of the D-loop strand. Many of the conserved sequence blocks (CSBs) observed in mammals are also found among fish. In particular, the mammalian CSB-D is present in all of the fish species studied. Study of potential secondary structures of RNAs from the conserved regions provides little insight into the functional constraints on these regions. The variable structure of these control regions suggests that particular care should be taken to identify the most appropriate segment for studies of intraspecific variation. Correspondence to: T.D. Kocher     

Modelling biological invasions: species traits,species interactions,and habitat heterogeneity

In this paper we explore the integration of different factors to understand, predict and control ecological invasions, through a general cellular automaton model especially developed. The model includes life history traits of several species in a modular structure interacting multiple cellular automata. We performed simulations using field values corresponding to the exotic Gleditsia triacanthos and native co-dominant trees in a montane area. Presence of G. triacanthos juvenile bank was a determinant condition for invasion success. Main parameters influencing invasion velocity were mean seed dispersal distance and minimum reproductive age. Seed production had a small influence on the invasion velocity. Velocities predicted by the model agreed well with estimations from field data. Values of population density predicted matched field values closely. The modular structure of the model, the explicit interaction between the invader and the native species, and the simplicity of parameters and transition rules are novel features of the model.     

Local species immigration,extinction, and turnover of butterflies in relation to habitat area and habitat isolation

Temporal dynamics of insect communities in terrestrial habitat fragments have been rarely studied. Here it was tested whether immigration, extinction, and turnover of butterfly species change with area and isolation of 31 calcareous grasslands. The area ranged from 0.03 to 5.14 ha, the isolation index from 2,100 to 86,000 (edge-to-edge distance 55–1,894 m). In both study years (1996, 2000), the total number of individuals (16,466, 15,101) and species (60, 54) sampled across all sites were similar and number of species increased with area in both years indicating an equilibrium. Rates of extinction (38% for habitat specialists vs. 20% for generalists) and turnover (51% vs. 35%) were higher, and rates of immigration (11% vs. 30%) were lower for habitat specialists than for generalists. Extinction and turnover rates decreased with increasing fragment size for both specialist (n =25 species) and generalist (n =36) butterflies, but specialists showed a significantly steeper decrease with increasing fragment size than generalists. Immigration rates increased with area. As a result, species number of habitat specialists declined in small habitats but not in large habitats between 1996 and 2000. No significant impact of habitat isolation on the butterfly community was found. The data suggest that large habitat fragments are of special importance for the conservation of the specialized, most endangered butterfly species. Habitat isolation appears to be less important, as butterflies can cope with the habitat mosaic in our study region.Due to an error in the citation line, this revised PDF (published in December 2003) deviates from the printed version, and is the correct and authoritative version of the paper.     

Generation of VNTRs and heteroplasmy by sequence turnover in the mitochondrial control region of two elephant seal species

We describe an unusual repetitive DNA region located in the 3′ end of the light (L)-strand in the mitochondrial control region of two elephant seal species. The array of tandem repeats shows both VNTR (variable-number tandem repeat) and sequence variation and is absent from 12 compared mammalian species, except for the occurrence in the same location of a distinct repetitive region in rabbit mtDNA and a similar repeat in the harbor seal. The sequence composition and arrangement of the repeats differ considerably between the northern elephant seal (Mirounga angustirostris) and the southern species (M. leonina) despite an estimated divergence time of 1 MY (based on an mtDNA-RNA gene and the nonrepetitive control region). Analysis of repeat sequence relationships within and between species indicate that divergence in sequence and structure of repeats has involved both slippagelike and unequal crossingover processes of turnover, generating very high levels of divergence and heteroplasmy. Presented at the NATO Advanced Research Workshop onGenome Organization and Evolution, Spetsai, Greece, 16–22 September 1992     

Phylogenetic relationship of two <Emphasis Type="Italic">Mola</Emphasis> sunfishes (Tetraodontiformes: Molidae) occurring around the coast of Japan,with notes on their geographical distribution and morphological characteristics

Phylogenetic analyses were conducted using complete nucleotide sequences of the D-loop in the mitochondrial genome of Mola specimens, collected mainly in Japanese waters, to clarify the genetic features and distribution patterns of Mola sunfishes. Two significantly distinct groups (designated A and B) were present in the genus, with a considerable net nucleotide sequence divergence between the two (8.4%). The two groups occurred sympatrically around the Japanese coast, as previously suggested by Sagara et al. (2005). Group A occurred mostly on the Pacific coast of eastern Japan, while group B was widely distributed along the Kuroshio Current, strongly suggesting different migration routes for each group. The morphological characteristics of the two group specimens were differentiated via the head bump, body proportions and shape of the clavus. Through the addition of Mola sequence data taken from outside Japan to our phylogenetic analyses, three independent groups, including groups A and B, were found, each with a wide geographical distribution, which suggests the presence of at least three independent species within the genus Mola.     

Phylogenetic analysis of <Emphasis Type="Italic">Verticillium</Emphasis> species based on nuclear and mitochondrial sequences

Three different genes were sequenced from isolates of five plant-pathogenic Verticillium species, Verticillium albo-atrum, Verticillium dahliae, Verticillium longisporum, Verticillium nigrescens, and Verticillium tricorpus. The sequences covered parts of the mitochondrial cytochrome b gene (cob), the mitochondrial small subunit rRNA gene (rns) and the nuclear ITS2 region. When the sequences were combined, the five species clustered in five monophyletic groups, with V. nigrescens distantly related to the other species while V. tricorpus displayed a somewhat closer relationship to the three remaining species. V. albo-atrum, V. dahliae and V. longisporum were found to be very similar to each other, with V. albo-atrum and V. longisporum displaying the closest relationship. The species affiliation of V. longisporum is discussed.     

The phylogeny of echinoderm classes based on mitochondrial gene arrangements

Summary Previous analyses have demonstrated that, among the echinoderms, the sea star (class: Asteroidea) mitochondrial genome contains a large inversion in comparison to the mitochondrial DNA of sea urchins (class: Echinoidea). Polymerase chain reaction amplification, DNA cloning, and sequencing have been used to examine the relationships of the brittle stars (class: Ophiuroidea) and sea cucumbers (class: Holothuroidea) to the sea stars and sea urchins. The DNA sequence of the regions spanning potential inversion junctions in both brittle stars and sea cucumbers has been determined. This study has also revealed a highly modified tRNA cluster in the ophiuroid mitochondrial genome. Our data indicate mitochondrial gene arrangement patterns that group the sea cucumbers with sea urchins and sea stars with brittle stars. This use of molecular characters clarifies the relationships among these classes.     

The relationship between nested subsets,habitat subdivision,and species diversity

Biotic assemblages are said to be nested when the species making up relatively species-poor biotas comprise subsets of the species present at richer sites. Because species number and site area are often correlated, previous studies have suggested that nestedness may be relevant to questions of how habitat subdivision affects species diversity, particularly with respect to the question of whether a single large, contiguous patch of habitat will generally contain more species than collections of smaller patches having the same total combined area. However, inferences from analyses of nestedness are complicated by (1) variability in degrees of nestedness measured in natural communities, (2) variability in species-area relationships, and (3) the fact that nestedness statistics do not account for the size of habitat patches, only in the degree of overlap among sites with different numbers of species. By comparing various indices of nestedness with a saturation index that more directly measures the effect of habitat subdivision, it is shown that the first two of these factors are not as important as the third. Whether a single large site or several smaller ones having the same total combined area maximizes species diversity is dependent on (1) overlap in species composition among sites and (2) the number of species per unit area in the different sites. Because nestedness indices do not account for species number at a site, they cannot accurately predict how habitat subdivision affects species diversity patterns. Still, nestedness analyses are important in that they indicate the degree to which rare species tend to be found in the largest, or the most species-rich, sites, patterns not revealed by the saturation index. Both types of analysis are important in order to obtain a more complete picture of how species richness and compositional patterns are influenced by habitat subdivision.