NOTE MOLECULAR ANALYSIS OF THE AHAS GENE OF PORPHYRIDIUM SP. (RHODOPHYTA) AND OF A MUTANT RESISTANT TO SULFOMETURON METHYL

Acetohydroxyacid synthase (AHAS) is the target enzyme of the sulfonylurea herbicides, and here we report the sequence of the gene from wild-type and herbicide-resistant Porphyridium sp. (Rhodophyta). The resistant mutant has a single residue substitution at a position known to confer herbicide resistance in E. coli and in plants. The rhodophyte gene is of cyanobacterial origin and distinct from the nuclear-encoded chlorophyte gene, which may be of mitochondrial origin.     

Ontogenetic Evidence for Dental Homologies and Premolar Replacement in Fossil and Extant Caenolestids (Marsupialia)

It is generally accepted that the South American marsupial family Caenolestidae is characterized in part by the absence or noneruption of the third deciduous premolar (dP3) in both jaws, although juvenile stages have rarely been identified in extant or fossil representatives of the family. Published illustrations of the dentary of the Miocene caenolestid Stilotherium suggested to us, however, that P3 erupted relatively late during ontogeny, after the eruption of M4. In extant marsupials, this eruption sequence appears to represent the plesiomorphic state and this pattern is generally associated with the eruption of dP3 earlier in ontogeny, and its subsequent replacement by the erupting P3. Therefore, we suspected that a dP3 erupted in earlier ontogenetic stages of caenolestids; to test this hypothesis we searched the mammalogy collections of three museums for evidence of dP3 in juvenile specimens of caenolestids. Examination of more than 180 specimens of the three extant genera of caenolestid marsupials resulted in the identification of only nine juvenile or subadult stages of dental eruption. Seven specimens of Caenolestes and Rhyncholestes corroborated our hypotheses of late eruption of P3 in Caenolestidae. In addition, the two youngest specimens of Caenolestes possessed a tiny, rudimentary dP3, measuring about 0.4 to 0.5 mm in greatest length, associated with a mesiolingual eruption pit containing the apex of the larger P3 in very early phases of eruption above the alveolar margins. The tiny dP3 is clearly nonfunctional in occlusion, and it is questionable whether it erupted above the gun margins in life. Comparison of the dentaries of subadult caenolestids with four dentaries of the Miocene genus Stilotherium corroborated our initial impression that the fossil genus exhibited evidence of a late-erupting P3, comparable to the condition in extant caenolestids. We suggest that examination of other specimens of juvenile dentitions, skulls, and skeletons in museum collections can provide additional insight into the developmental and evolutionary biology of mammals.     

楠木名称考订

<正> 经过多年对楠木的研究,我们发现楠木的正确学名应该修订。驰名中外的“楠木”,是很有趣的珍贵树种,它包括樟科润楠属(Machilus Nees)和楠属(Phoebe Nees)植物的一些近缘种,在四川及云南,一般把Phoebe zhennan,Phoebe hui和Machilus pingii通称为楠木,而在福建、浙江、贵州及广东、广西,却把Phoebe bournei称为楠木。自1877年英人A.Davenport在Kew Report报道了关于中国楠木的消息后,楠木的名称开始在植物学界造成乱混。D.Oliver于1879年把A.Davenport、E.Bradford和F.Vincot     

核骨架——细胞核内生命活动的重要结构体系

综合分析了国际国内近年来有关核骨架研究的新进展,从几个方面的研究事实,包括核骨架对染色质ＤＮＡ的有序组织,核骨架参与ＤＮＡ复制和基因的表达与调控以及核骨架的起源进化等,阐明核骨架是细胞核内染色质结构的有序组织者和功能活动的参与者,核内纷繁复杂的生命活动能有条不紊地进行,核骨架在其中扮演了重要角色。     

GENOMICS IN THE LIGHT OF EVOLUTIONARY TRANSITIONS

Molecular biology has entrenched the gene as the basic hereditary unit and genomes are often considered little more than collections of genes. However, new concepts and genomic data have emerged, which suggest that the genome has a unique place in the hierarchy of life. Despite this, a framework for the genome as a major evolutionary transition has not been fully developed. Instead, genome origin and evolution are frequently considered as a series of neutral or nonadaptive events. In this article, we argue for a Darwinian multilevel selection interpretation for the origin of the genome. We base our arguments on the multilevel selection theory of hypercycles of cooperative interacting genes and predictions that gene‐level trade‐offs in viability and reproduction can help drive evolutionary transitions. We consider genomic data involving mobile genetic elements as a test case of our view. A new concept of the genome as a discrete evolutionary unit emerges and the gene–genome juncture is positioned as a major evolutionary transition in individuality. This framework offers a fresh perspective on the origin of macromolecular life and sets the scene for a new, emerging line of inquiry—the evolutionary ecology of the genome.     

THE SEX-RATIO TRAIT IN DROSOPHILA SIMULANS: GEOGRAPHICAL DISTRIBUTION OF DISTORTION AND RESISTANCE

The sex-ratio trait we describe here in Drosophila simulans results from X-linked meiotic drive. Males bearing a driving X chromosome can produce a large excess of females (about 90%) in their progeny. This is, however, rarely the case in the wild, where resistance factors, including autosomal suppressors and insensitive Y chromosomes, prevent the expression of the driver. In this study, we searched for drive and resistance factors in strains of Drosophila simulans collected all over the world. Driving X chromosomes were found in all populations whenever a good sample size was available. Their frequency may reach up to 60%. However, the presence of driving X chromosomes never results in an excess of females, due to the systematic co-occurrence of resistance factors. The highest frequencies of driving X chromosomes were observed in islands, while populations from East and Central Africa (the supposed center of origin of the species) showed the highest level of resistance. The geographical pattern of drive and resistance factors, as well as the results of crosses between strains from different geographical areas, suggest that the sex-ratio system described here has a unique and ancient origin in the species.     

THE ORIGIN OF THE LAND PLANT SPOROPHYTE: AN INTERPOLATIONAL SCENARIO

The origin of terrestrial plants from a charophycean ancestor is assumed as a basis for the consideration of the origin of life histories amongst this group. Charophycean algae are vegetatively gametophytic, thus requiring the interpolation of the multicellular sporophytic stage. The model presented here derives the sporophyte and typical sporangial contents from the zygospore produced from the reproductive structure of a hypothetical charophycean land plant ancestor. The presence of monads, dyads, and various forms of tetrads in the fossil record of presumed land plants add support to this model. In addition, such spore types suggest that the temporal relationship of meiosis to sporopollenin deposition was less strictly controlled than in extant land plants.     

THE EVOLUTION OF LANDSCAPE GENETICS

The main objective of this special section is not to review the broad field of landscape genetics, but to provide a glimpse of how the developing landscape genetics perspective has the potential to change the way we study evolution. Evolutionary landscape genetics is the study of how migration and population structure affects evolutionary processes. As a field it dates back to Sewall Wright and the origin of theoretical population genetics, but empirical tests of adaptive processes of evolution in natural landscapes have been rare. Now, with recent developments in technology, methodology, and modeling tools, we are poised to trace adaptive genetic variation across space and through time. Not only will we see more empirical tests of classical theory, we can expect to see new phenomena emerging, as we reveal complex interactions among evolutionary processes as they unfold in natural landscapes.     

A NEW PRIMITIVE CHALICOTHERE (PERISSODACTYLA,MAMMALIA) FROM THE EARLY EOCENE OF HUBEI, CHINA

'I.DESCR1PTIoNorderPerissodactylaOwen,l848SuperfamilyCbalicotherioideacall,l872'Family?EomoropidaeVret,l958GehusDanjiangiagen.nov.TypespeciesDaniiangiapingigen.etsp-nov.DiagnoaisSma1lprimitivecha1icothere(lengthofM/l=8.3mm),skullshallowwithcranialrostrumrelatively1ong,mandibularhorizontalramusandmandibularsymphysisfairlylongandsha1low,teeth1ow-crowned,dentitionformula:3.l.4.3/3.1.4.3.Premolarnonmolariform,P2/2tIenchant,P4/withincipientmesostyle.M/widerthan1engthwithW-shapedectoIoph,…     

痕迹化石在识别东濮凹陷古近纪河口湾环境和下切谷中的作用

河口湾砂岩储层,在下切谷型油气勘探类型中极具潜在经济价值,因而引起众多沉积环境研究者的关注。河口湾是河水、海水相互作用的场所,具明显的三重沉积结构,即在河口湾内侧,河流淡水沉积具主导;在河口湾外侧,则以潮汐或波浪等海水水流沉积占优;而河口湾的中央地带,是海水和淡水汇合区,表现出咸水水体和低能环境的沉积特征。东濮凹陷沙河街组四段,低位期形成的下切谷和高位期转变成河口湾的过程,由沉积柱子中的海水生物痕迹、咸水生物痕迹及淡水生物痕迹记录下来,这些适应于不同水体的造迹生物所留下的痕迹,弥补了这一地区缺乏标志性实体化石带来的认识障碍,为识别其沉积环境真面目找到了新途径。由Cylindricum-Scoyenia为代表的淡水痕迹化石组合,以Tigillites和喜盐植物根迹为代表的咸水生物痕迹和以Thalassinoides,Teichichnus为代表的海水生物痕迹,在东濮凹陷沙河街组四段钻取的岩芯中多次出现,证实了那里河口湾沉积的三重结构和下切谷的存在。     

A DISCUSSION AND PROPOSAL CONCERNING THE USE OF THE TERM CALCISPHERES

Abstract:  The terminology and grouping of spherical, calcareous microfossils of unknown biological affinity, usually referred to as calcispheres, are diffuse. The term calcispheres is inconsistently used, the morphological and taxonomical concepts are mostly ill-defined and a formal definition is lacking. To resolve this issue, we propose, in analogy with the erection of the Acritarcha for organic microfossils of unknown origin, a new group called Calcitarcha, including all calcareous microfossils with a central cavity for which the biological affinities remain unknown.     

贵州下寒武统牛蹄塘生物群中海绵新材料

描述了贵州下寒武统牛蹄塘生物群中海绵化石1新属(Zunyispongiagen.nov.),2新种(Zunyispongiatriangulariagen.etsp.nov.,Choiafanensis.sp.nov.),通过对其形态功能的分析和讨论证实了寒武纪早期海绵动物的骨骼是由细小骨针向粗大骨针演变,骨架结构从不稳定型向稳定型发展。     

陕南早寒武世早期Quadrapyrgites再研究

处于"寒武纪生命大爆发"序幕阶段的梅树村期,生物类群大规模辐射,身体构型快速革新,与前寒武纪生物群面貌明显不同.最近在陕南宁强宽川铺地区梅树村期地层中发现了大量五辐射Punctatus及部分四辐射四方塔形壳属Quadrapyrgites,其中包括1个新种Quadrnpyrgites undulatuscostalis sp.nov..在此基础上对Quadrapyrgites进行了属征补充.双胚层腔肠动物的出现标志着地球生命史的真后生动物演化开端,在生物起源演化历程上占据着关键的位置.本文为研究真后生动物起源演化、生物辐射、体型构建提供了重要实证.     

HIGH RATES OF EVOLUTION PRECEDED THE ORIGIN OF BIRDS

The origin of birds (Aves) is one of the great evolutionary transitions. Fossils show that many unique morphological features of modern birds, such as feathers, reduction in body size, and the semilunate carpal, long preceded the origin of clade Aves, but some may be unique to Aves, such as relative elongation of the forelimb. We study the evolution of body size and forelimb length across the phylogeny of coelurosaurian theropods and Mesozoic Aves. Using recently developed phylogenetic comparative methods, we find an increase in rates of body size and body size dependent forelimb evolution leading to small body size relative to forelimb length in Paraves, the wider clade comprising Aves and Deinonychosauria. The high evolutionary rates arose primarily from a reduction in body size, as there were no increased rates of forelimb evolution. In line with a recent study, we find evidence that Aves appear to have a unique relationship between body size and forelimb dimensions. Traits associated with Aves evolved before their origin, at high rates, and support the notion that numerous lineages of paravians were experimenting with different modes of flight through the Late Jurassic and Early Cretaceous.     

ON THE PARADIGM OF ALTRUISTIC SUICIDE IN THE UNICELLULAR WORLD

Altruistic suicide is best known in the context of programmed cell death (PCD) in multicellular individuals, which is understood as an adaptive process that contributes to the development and functionality of the organism. After the realization that PCD‐like processes can also be induced in single‐celled lineages, the paradigm of altruistic cell death has been extended to include these active cell death processes in unicellular organisms. Here, we critically evaluate the current conceptual framework and the experimental data used to support the notion of altruistic suicide in unicellular lineages, and propose new perspectives. We argue that importing the paradigm of altruistic cell death from multicellular organisms to explain active death in unicellular lineages has the potential to limit the types of questions we ask, thus biasing our understanding of the nature, origin, and maintenance of this trait. We also emphasize the need to distinguish between the benefits and the adaptive role of a trait. Lastly, we provide an alternative framework that allows for the possibility that active death in single‐celled organisms is a maladaptive trait maintained as a byproduct of selection on pro‐survival functions, but that could—under conditions in which kin/group selection can act—be co‐opted into an altruistic trait.     

THE ORIGIN OF AFRO-ARABIAN 'DIDELPHIMORPH' MARSUPIALS

Abstract:  New specimens of Peratherium africanum from Early Oligocene deposits of the Fayum, Egypt, provide key information on the relationships of the species. These include the first maxilla to be found and two additional dentaries. The maxilla can be demonstrated to belong to the same species as the holotype dentary by study of the occlusal relationships of upper and lower molars. It can be shown by several synapomorphies that P. africanum is the sister species to European Bartonian–Rupelian Peratherium lavergnense . P. africanum therefore belongs to the 'didelphimorph' family Herpetotheriidae, not to the peradectimorph family Peradectidae. The genus Qatranitherium , previously erected for this species alone, is here synonymized with Peratherium . Comparison with 'didelphimorphian' taxa from early Paleogene deposits of South America suggests more remote relationships, indicating an origin for P. africanum by dispersal from Europe as originally envisaged. The more precise relationships deduced here help to constrain the time interval for dispersal to Afro-Arabia, probably during the earliest Oligocene sea-level low.     

LOCOMOTOR MODULES AND THE EVOLUTION OF AVIAN FLIGHT

The evolution of avian flight can be interpreted by analyzing the sequence of modifications of the primitive tetrapod locomotor system through time. Herein, we introduce the term “locomotor module” to identify anatomical subregions of the musculoskeletal system that are highly integrated and act as functional units during locomotion. The first tetrapods, which employed lateral undulations of the entire body and appendages, had one large locomotor module. Basal dinosaurs and theropods were bipedal and possessed a smaller locomotor module consisting of the hind limb and tail. Bird flight evolved as the superimposition of a second (aerial) locomotor capability onto the ancestral (terrestrial) theropod body plan. Although the origin of the wing module was the primary innovation, alterations in the terrestrial system were also significant. We propose that the primitive theropod locomotor module was functionally and anatomically subdivided into separate pelvic and caudal locomotor modules. This decoupling freed the tail to attain a new and intimate affiliation with the forelimb during flight, a configuration unique to birds. Thus, the evolution of flight can be viewed as the origin and novel association of locomotor modules. Differential elaboration of these modules in various lineages has produced the diverse locomotor abilities of modern birds.     

进化细胞生物学的提出及其任务

作者提出应创建一门源于进化生物学与细胞生物学两者的交叉学科一进化细胞生物学(细胞的进化生物学)。其根本任务在于用进化的观点考察真核细胞的一切方面,从它们的起源和演化来认识它们的现在。文中列举了其具体的研究内容,并分析了其研究方法上的特点,指出在这里需要把进化生物学的综合性分析与细胞生物学的实验研究最紧密地结合起来。文中还论述了真核细胞的细胞器的“不进化”现象,指出其根本原因在于进化焦点的转移。     

PHYLOGENY OF THE SUBFAMILIES OF THE FAMILY BRACONIDAE: A REASSESSMENT ASSESSED

Abstract— Wharton et al. (1992) provided an extensive reappraisal of the phylogenetic analysis of the subfamilies of Braconidae by Quicke and van Achterberg (1990). In this critique they drew attention to a number of errors in our data matrix and made a number of useful suggestions regarding character coding and polarization. However, they also make a number of erroneous statements that, if anything, present our work in a worse light. We therefore provide here some discussion of the comments by Wharton et al. indicating where we are in agreement and where we believe our initial interpretations were correct. We also take this opportunity to correct some additional mistakes that have subsequently been unearthed in our original data matrix.     

新疆玛纳斯古近纪—新的鲤科鱼类

记述了新疆玛纳斯古近纪安集海河组发现的鲤科(Cyprinidae)一新属、种——刘氏天山鱼(Tianshanicus liui gen.et sp.nov.)。新属具有臀鳍分叉鳍条多于7根、体长形稍侧扁、口端位、下咽齿近锥形而齿尖前后略侧扁、背鳍和臀鳍均无硬棘、背鳍起点略在腹鳍起点之后以及尾鳍深分叉等特征,表明它应属于雅罗鱼亚科(Leuciscinae sensu Cavender & Coburn,1992)。然而,它又具有额骨前宽后窄、顶骨长方形、膜质蝶耳骨很大、齿骨冠状突较低、鳃盖骨近长方形等特征而有别于本亚科中其他属。值得注意的是,这些特征却见诸于现生的胭脂鱼类Myxocyprinus中,这将对研究雅罗鱼类的起源很有意义。根据鱼化石和哺乳化石的证据,认为含鱼层的时代为晚始新世。