A HYPOTHESIS ON THE EVOLUTIONARY ORIGIN OF THE SQUAMOSAL BONE IN THE THERIAN MAMMALS

Theatheriansandthetherianshavebothinheritedthesquamosa1fromthecyno-dontidancestry,theprimitivepropertyofthesquamosa1intheatherianlineagehavebeenmaintainedfromthebeginning(theLateTriassic,Morganucodontids)totheend(Cretaceous,Triconodontids).Inthetherianlineage,thelowertherianshavethesamesquamosalastheatherians,however,thehighertherianshaveapeculiarsquamosal,so,thechangeofthepropertyofthesquamosaImaytakeplacelntheevolutionaryphasefromthelowertherianmammals(Symmetrodonta,Eupan-totheria,Multitu…     

美丽马醉木叶化学成分的研究

从美丽马醉木(Pieris formosa D.Don)叶中分离得到马醉木亭(Ⅰ)、β-谷甾醇(Ⅱ)、β-香树脂醇(Ⅲ),蒲公英醇(Ⅳ)4个已知化合物。     

介形类系统分类与起源演化的形态、分子和化石证据

介形类(Ostracoda)因其丰富的化石记录和广布的海陆现生代表类群,而被认为是进化生物学中研究生物多样性产生机制和演变历程的颇具潜力的重要模式生物。介形类在甲壳亚门中的谱系发生位置、起源及其内部各类群间的系统关系还存在诸多争议。基于其体制构造的形态学特征,介形类被归入甲壳亚门下的颚足纲(Maxillopoda),但来自18S rDNA序列数据分析却显示Maxillopoda不是单系群。基于化石记录和壳体形态特征,高肌虫(Bradoriida)长期以来被认为是介形类的一个祖先类群,但保存有软躯体的早寒武世化石的研究表明,Bradoriida不是介形类甚至可能也不属于甲壳类。不同的研究者所强调的壳体和肢体形态特征各异,导致介形类最大的现生类群速足目(Podocopida)的四个超科之间的关系也存在诸多推测。壳体和肢体特征在系统演化意义上的不兼容,需要分子生物学等证据的介入。分子、形态和化石证据的积累及各种信息整合是系统演化研究的必然趋势。     

沟鞭藻的起源:分子地球化学证据

沟鞭藻为单细胞的原始的海洋生物。古生物学家根据形态特征,超微结构和生物化学信息认为沟鞭藻可能在前寒武纪时已存在,并推测古生代疑源类可能是现代沟鞭藻的先祖,但确凿的沟鞭藻囊孢的化石记录始于晚三叠世。生物标志物以分子化石的形式记录了沟鞭藻的起源及演化历史。在古生代及前寒武纪地层中甲藻甾烷及三芳沟鞭藻的检出,建立了沟鞭藻与其古代先祖（疑源类）的联系,提供了沟鞭藻先祖前寒武纪存在的证据。     

FUNGAL CONTROL OF POPULATION CHANGES OF THE PLANKTONIC DIATOM ASTERIONELLA FORMOSA IN A SHALLOW EUTROPHIC LAKE1

Parasitic fungi infected an Asterionella formosa Hass. population for 10 months of the year, during which time the population density of the alga was over 100 cells-L^?1. High injection rates of more than 20% of the cells were observed between February and July except on a few occasions such as late April and late June. Mortality of infected diatom cells was temperature dependent in dialysis tube culture experiments; the loss rate of field populations due to fungal injection also was affected by temperature. Loss rates of diatom cells were negligibly small m February even though infection percentages were more than 20%, but increased toward summer with an increase m temperature. High infection percentages and correspondingly high loss rates (e.g. 0.3 d^?1) occurred periodically during the summer. The results suggest that this type of host-parasite interaction is an important control of algal population size in natural waters.     

PARSIMONY,MOLECULAR EVOLUTION,AND BIOGEOGRAPHY: THE CASE OF THE NORTH AMERICAN GIANT SALAMANDER

To draw biogeographic conclusions about the Central Highlands region of the United States, we reconstructed the phylogeny of hellbender (Cryptobranchus alleganiensis) populations from restriction-site variation in mtDNA. We were unable to root the phylogeny using an outgroup and therefore could not weight restriction-site gains more heavily than site losses. As a result, maximum parsimony results in low phylogenetic resolution because of high levels of homoplasy in the data set. Use of a recently published algorithm based on an explicit model of molecular evolution yielded much greater resolution of the mtDNA relationships. This phylogeny indicates the two subspecies of hellbenders are paraphyletic with respect to one another. Hellbenders found in the southern Ozarks (C. a. bishopi) are either most closely related to populations of C. a. alleganiensis inhabiting the Tennessee River drainage or are so divergent that phylogenetic affinities are undetectable. Extremely low levels of divergence among mtDNA haplotypes found in populations from Pennsylvania, Indiana, Illinois, and the northern Missouri Ozarks suggest a recent, probably post-Pleistocene, invasion of this region from a refugium in one of these areas. Biogeographic hypotheses of the causes and timing of hellbender distributions differ significantly from those postulated from analyses of fish species relationships. Possible reasons for the discrepancy are discussed.     

AN ADDITIONAL PUNCTATE SPECIES OF PYRAMIMONAS, P. FORMOSA, SP. NOV., AND ITS IMPACT ON THE SUBGENERA PUNCTATAE AND PYRAMIMONAS (PRASINOPHYCEAE, CHLOROPHYTA)

A new punctate species of Pyramimonas Schmarda from South Africa is described. This species is somewhat anomalous and, like P. chlorina Sym et Pienaar (subgenus Pyramimonas McFadden), has characters that bridge the divide between the subgenera Pyramimonas and Punctatae McFadden. Features of these two species, together with the lack of exclusive character sets for either subgenus derived from other species of these subgenera, lead to the conclusion that Punctatae now should be subsumed formally into the subgenus Pyramimonas.     

紊蒿属一新种和对该属分类及演化的讨论

对新种多头紊蒿(Elachanthemum polycephalum Z.Y.Zhu et C.Z.Liang)的形态特征进行了描述,并从形态和生态特征、地理分布及其区系起源等方面探讨了紊蒿属(Elachanthemum Y.Ling et Y.R.Ling)的分类地位。结果表明：紊蒿属与百花蒿属(Stilpnolepis Krasch.)在形态上虽有相近之处,但花、果实和花粉等形态差异明显,因而不能并入百花蒿属,而应独立成属。该属起源于第三纪亚洲北部的古蒿类群(Pro-Artemisia L.),是蒿类中较为原始的属,为古地中海东部残遗的旱生成分,也是现代亚洲中部荒漠(戈壁荒漠)的持有属;多头紊蒿新种的发现,使紊蒿属从单种属变成寡种(双种)属,表明荒漠植物区系的物种分化仍在进行。     

使用分子遗传学方法对版纳鱼螈分布、起源及扩散的初步研究

版纳鱼螈Ichthyophis bannanicus是蚓螈目Gymnophiona在我国分布的唯一物种.由于长期以来缺乏对版纳鱼螈的分布范围及演化历史等信息的了解,本研究通过分子遗传学的方法,就其分布、起源及扩散等内容进行了探讨.结果发现,我国境内的版纳鱼螈均属同一物种,尚未出现种的分化.研究中明确证实了版纳鱼螈在泰国和越南的分布,提示了版纳鱼螈在中南半岛广为分布,甚至可能达到马来西亚境内.结果还提示水系对版纳鱼螈的分布具有较大的影响,尤其在湄公河水系中表现的最为明显.现有的信息提示版纳鱼螈有可能起源于中南半岛,并沿着澜沧江-湄公河水系、红河-珠江水系、克拉地峡-马来半岛3个方向扩散.我国境内的版纳鱼螈主要分布在云南南部地区和两广丘陵以南,来自这两大分布区的个体之间的遗传差异明显,应属于不同的进化显著单元.     

GENE GENEALOGY AND DIFFERENTIATION AMONG ARBOREAL SPINY RATS (RODENTIA: ECHIMYIDAE) OF THE AMAZON BASIN: A TEST OF THE RIVERINE BARRIER HYPOTHESIS

Sequence variation in the mitochondrial cytochrome b gene was examined in the arboreal spiny rat, Mesomys hispidus, collected at 15 sites along the Rio Juruá in western Amazonia, Brazil, to determine the importance of riverine barriers in the diversification of this taxon. Twenty individual haplotypes were uncovered, most of which were unique to single localities but some of which were shared among adjacent sites either along or across the river. Genealogical analyses suggest that gene flow is limited and, in combination with the unique distribution of most haplotypes, suggest that populations of this species are strongly substructured along the river. Thus, most sharing of haplotypes between adjacent localities is probably caused by historical association rather than to ongoing gene flow. Two haplotype clades were uncovered, but these correspond to headwaters versus mouth areas, not to opposite sides of the river, as would be expected by the Riverine Barrier Hypothesis. Moreover, haplotype sharing across the river was greater at its mouth than in the headwaters, a pattern opposite that expected if the river were a substantive barrier. Broader scale phylogeographic patterns of this species show that both clades have relationships to areas well outside the Rio Juruá basin. This suggests that the basin represents a relatively recent point of invasion between two more broadly distributed and differentiated geographic units of the species.     

A SPECIATIONAL HISTORY OF “LIVING FOSSILS”: MOLECULAR EVOLUTIONARY PATTERNS IN HORSESHOE CRABS

Horseshoe crabs' exceptional morphological conservatism over the past 150 My has led to their reputation as “living fossils,” but also has served to obscure phylogenetic relationships within the complex. Here we employ nucleotide sequences from two mitochondrial genes to assess molecular evolutionary rates and patterns among all extant horseshoe crab species. The American species Limulus polyphemus proved to be the sister taxon to a clade composed of the Asiatic species Tachypleus gigas, T. tridentatus, and Carcinoscorpius rotundicauda, whose relationships inter se were not resolved definitively. Both absolute and relative rate tests suggest a moderate slowdown in sequence evolution in horseshoe crabs. Nonetheless, dates of the lineage separations remain uncertain primarily because of reservations about molecular-clock calibrations resulting from large rate variances at examined loci across Arthropods and other animal lineages, as inferred in this and prior studies. Thus, ironically, separation dates as estimated by molecular evidence in general may remain most insecure in taxonomic groups for which such information is needed most—those lacking strong biogeographic or fossil benchmarks for internal-clock calibrations. In any event, the current results show that large numbers of molecular characters distinguish even these most morphologically conservative of organisms. Furthermore, comparisons against previously published mitochondrial sequence data in the morphologically dynamic hermit crab–king crab complex demonstrates that striking heterogeneity in levels of morphotypic differentiation can characterize Arthropod lineages at similar magnitudes of molecular divergence.     

THE EVOLUTIONARY HISTORY OF PARTHENOGENETIC CNEMIDOPHORUS LEMNISCATUS (SAURIA,TEIIDAE). I. EVIDENCE FOR A HYBRID ORIGIN

Chromosomes and allozymes were studied from chromosomally distinct unisexual (races B and C) and bisexual (races D and E) populations of the teiid lizard Cnemidophorus lemniscatus, and from selected outgroup taxa (C. murinus, C. nigricolor, Ameiva ameiva, and A. auberi). Karyotyping confirmed the racial identity of individuals and showed that the chromosomal composition of populations at specific localities has remained the same for 20 years. All individuals of both unisexual populations were heterozygous for a pericentric inversion that distinguishes D and E bisexuals. Also, the unisexuals were all heterozygous for 8 of 11 protein loci for which D and E were fixed or nearly fixed for different alleles. Most of these alleles represent derived states relative to the other Cnemidophorus and Ameiva analyzed, and the fixed heterozygote condition at these nine markers provides unequivocal support for the hypothesis that the unisexual C. lemniscatus arose by hybridization between ancestors genetically similar to extant D and E populations. At the remaining three loci for which D and E show fixed differences, the unisexuals were homozygous rather than heterozygous. This suggests that either (1) allozymes have been lost by mutations to null, silent, or convergent mobility states, (2) ancestral genotypes were similar to but not identical with the extant D and E races, and/or (3) limited recombination may occur between unisexual genomes. Allozyme-based genetic distances between D and E were large, suggesting that bisexual races D and E are genetically isolated; each race should be accorded full species status. This conclusion is supported by the absence of any clear biochemical evidence for their monophyly with respect to the other Cnemidophorus examined. Cladistic analyses of 17 phylogenetically informative loci revealed two equally parsimonious shortest trees, one supporting monophyly and the other paraphyly of the C. lemniscatus complex. Further testing of the monophyly of C. lemniscatus requires additional data. With the present study, the evidence that all parthenogenetic Cnemidophorus are of hybrid origin is complete.     

黑龙江方正银鲫雌核发育的细胞学初步探讨

雌核发育是一种特殊的繁殖方式,同种或异种精虫进入卵细胞内只刺激其发育,精虫头部并不形成有功能的雄性原核,结果卵细胞的发育只是在一个雌性原核的参与下进行(洛马索夫,1960)。许多研究报告证实银鲫用这种方式繁殖后代。Berg 1949年首次提出银鲫(Carassius auratus gibelio)雌核发育的假设,其后洛马索夫和哥洛温斯卡娅(1947,1954)用黑龙江移殖的银鲫雌鱼与鲫、野鲤、家鲤等雄鱼杂交,得到的后代完全与银鲫同型,并用细胞学方法证实了雄性精核在卵细胞的发育过程中没有与卵核融合。1966年,Cherfas报道了黑龙江一种雌核发育银鲫的染色体为三倍体。1971、1978年,小林弘先后发表了日本关东系三倍体银鲫(Carassius auratus lagsdorfii)雌核发育的细胞学研究报告,     

斯氏鼢鼠物种地位有效性的探讨

为了探讨斯氏鼢鼠的物种地位,分别测得了4个斯氏鼢鼠、3个高原鼢鼠、2个秦岭鼢鼠个体的线粒体细胞色素b基因和12SrRNA基因的全序列,结合下载自Gen Bank中的鼢鼠序列,利用MEG A4.0,PH YLIP 3.57c软件包和Mrbayes 3.1.2软件以中华竹鼠做外群分别重建鼢鼠亚科的系统发育关系,并比较了采自3个地区的斯氏鼢鼠、高原鼢鼠和秦岭鼢鼠的头骨形态学特征。分子生物学研究结果支持斯氏鼢鼠的物种地位,且与秦岭鼢鼠和高原鼢鼠的亲缘关系较近。     

雌核发育银鲫的受精生物学研究——天然雌核发育银鲫繁殖方式的讨论

本文研究了同源雌核发育银鲫精子在4种类型的雌核发育银鲫卵中的发育特征。初步揭示了天然雌核发育银鲫根据精子的来源不同而分别具有二种不同的繁殖方式,对其在维持雌核发育银鲫种群生存,促使克隆分化等方面的独特的生物学意义进行了讨论。     

马鸡的分类、分布及演化关系的初步探讨

（１）在耳羽簇发达程度，尾羽形状，腓肠肌外支腿膜内的种子骨和第二趾收肌，雄鸡间争偶和占区行为，巢址选择，瓣生雏形态等方面，白马鸡和藏马鸡，蓝马鸡和褐钯鸡分别表现出明显不同的一致性。基于此，我们认为白马鸡和藏马鸡是原始的类型，蓝马鸡和褐马鸡有较近的亲缘关系。（２）青藏高原短暂的隆起历史和相应发生的生态环境的复杂变化，是白马鸡各亚种形态多变而不稳定的主要原因。与白马鸡相比，藏马鸡的体色特化而稳定，结合     

新生牛肝中低分子抑瘤物影响白血病细胞生长的实验研究

新生牛肝经匀浆、离心和分级超滤后,得到分子量≤1.0kDa的、耐热的成分——新生牛肝抑瘤物(new-bom calfliver suppressor,BLS-1)。对BLS-1的生物学活性进行了检测,结果表明在体外液体和半固体琼脂培养条件下,它对人和小鼠白血病细胞系(如HL-60、L833 和 P388 等)的生长均有明显的抑制作用,并存在着一定的量效关系;与同样条件下BLS-1对人和小鼠正常粒-巨噬系祖细胞的抑制作用相比较,BLS-1对白血病细胞生长的抑制作用具有较强的选择性。进一步观察了BLS-1对5例急性非淋巴细胞白血病病人骨髓的原代白血病细胞集落(leukemic blast progenitor,L-CFU)生成的影响,结果表明,当BLS-1的浓度达到500μg/ml时,L-CFU的生成受到明显抑制。上述研究结果提示,在新生牛肝中可能存在类似于人胎儿肝脏中的一类低分子天然抑瘤物。