Comparative Ultrastructure and the Evolution of Nemertines

Nemertines are traditionally viewed as acoelomates with bloodvascular systems and a specialized cavity housing an eversibleproboscis, or, as coelomates with modified coelomic cavitiesforming the rhynchocoel, lateral vessels and gonadal sacs. Comparativeultrastructural data such as cell polarity, the occurrence ofpodocytes and mesodermal cells with rudimentary cilia for proboscis,rhynchocoel, lateral and dorsal vessels, and gonadal liningsare consistent with their interpretation as modified coelomiccavities as found, analogously, in the higher leeches. Theseand additional data regarding musculature, connective tissue,glia-like cells and gametes for 13 species affirm that nemertinesare intermediate between full-blown coelomate and acoelomategrades of organization. A comparison of ultrastructural details,however, indicates that their acoelomate attributes evolvedsecondarily from a more typical coelomate condition.     

Thermodynamics of Terrestrial Evolution

The causal element of biological evolution and development can be understood in terms of a potential function which is generalized from the variational principles of irreversible thermodynamics. This potential function is approximated by the rate of entropy production in a configuration space which admits of macroscopic excursions by fluctuation and regression as well as microscopic ones. Analogously to Onsager's dissipation function, the potential takes the form of a saddle surface in this configuration space. The path of evolution following from an initial high dissipation state within the fixed constraint provided by the invariant energy flux from the sun tends toward the stable saddle point by a series of spontaneous regressions which lower the entropy production rate and by an alternating series of spontaneous fluctuations which introduce new internal constraints and lead to a higher entropy production rate. The potential thus rationalizes the system's observed tendency toward "chemical imperialism" (high dissipation) while simultaneously accommodating the development of "dynamic efficiency" and complication (low dissipation).     

莽山自然保护区陆生贝类多样性及其分布

于2001年5～9月对莽山自然保护区的陆生贝类进行了广泛调查,共采得陆生贝类39种,隶属于2亚纲10科19属,主要有环1：3螺科、烟管螺科、钻头螺科、拟阿勇蛞蝓科、坚齿螺科、巴蜗牛科、野蛞蝓科和嗜粘液蛞蝓科。对它们的种类分布、种群数量、区系与生态分布特点进行了分析。     

Early Terrestrial Animals, Evolution, and Uncertainty

Early terrestrial ecosystems record a fascinating transition in the history of life. Animals and plants had previously lived only in the oceans, but, starting approximately 470 million years ago, began to colonize the previously barren continents. This paper provides an introduction to this period in life??s history, first presenting background information, before focusing on one animal group, the arthropods. It gives examples of the organisms living in early terrestrial communities and then outlines a suite of adaptations necessary for survival in harsh terrestrial environments. Emphasis is placed on the role of uncertainty in science; this is an integral part of the scientific process, yet is often seized upon by god-of-the-gaps creationist arguments. We hope to illustrate the importance of both uncertainty and scientists?? freedom to express doubt while a consensus is being built.     

浙江陆生贝类区系及其生态分布分析

1978、1979、2002年先后对浙江省20个县、市和地区进行了陆生贝类的初步调查,获得一批陆生贝类标本,经整理鉴定得43种和亚种,分隶13科,26属和亚属。同型巴蜗牛B．（B．）similaris similaris（Fernssac）、灰尖巴蜗牛B．（Acusta）ravida ravida（Benson）、野缨蛞蝓D．（A．）agreste（Linne）为广分布种类。根据本地区的地理条件及陆生贝类区系组成,东洋界为其主要成分,古北界少数种类渗入到本地区。其动物地理学分布基本上与中国动物地理划分相吻合。     

槭属的系统演化与地理分布

槭属（ＡｃｅｒＬ）属槭树科（Ａｃｅｒａｃｅａｅ）,２００种,分布于亚、欧、北美和非洲北缘。本文研究了槭属的系统演化、地理分布、起源与扩散。认为：（１）槭树科与无患子科关系密切,槭属是槭树科２属中较进化的类群。（２）在原始而典型的槭属植物的基础上,槭属沿花的各部减少,有的器官甚至向完全退化的方向演化,但也有少数向增加数目的方向特化。（３）讨论了槭属４亚属２３组的演化趋势,并绘制出其系统演化图。（４）槭属起源于侏罗纪的中国四川东部、湖北、湖南及其邻近地区,并向西、东北和南方扩散而进入西亚、欧洲、非洲北缘、北美洲和马来半岛至印尼。     

Evolution of Early Thule Material Culture: Cultural Transmission and Terrestrial Ecology

We investigate how evolution proceeds across multiple scales considering culture as species, hierarchically integrated systems, assemblages of many coherent units, and collections of ephemeral entities in order to examine the nature of Early Thule cultural evolution with reference to material culture and adaptive strategies. Results suggest that harpoon heads evolved via cultural transmission processes with little impact from terrestrial ecological context. In contrast, characteristics of architectural features, stone tool assemblages, and combined architecture and stone tools displayed evidence for significant effects of both cultural transmission and select measures of ecological context. There is no evidence that evolution was ‘evoked’ by ecological context alone.     

Distribution of Crenarchaeota Representatives in Terrestrial Hot Springs of Russia and Iceland

Culture-independent (PCR with Crenarchaeota-specific primers and subsequent denaturing gradient gel electrophoresis) and culture-dependent approaches were used to study the diversity of Crenarchaeota in terrestrial hot springs of the Kamchatka Peninsula and the Lake Baikal region (Russia) and of Iceland. Among the phylotypes detected there were relatives of both cultured (mainly hyperthermophilic) and uncultured Crenarchaeota. It was found that there is a large and diverse group of uncultured Crenarchaeota that inhabit terrestrial hot springs with moderate temperatures (55 to 70°C). Two of the lineages of this group were given phenotypic characterization, one as a result of cultivation in an enrichment culture and another one after isolation of a pure culture, “Fervidococcus fontis,” which proved to be a moderately thermophilic, neutrophilic (optimum pH of 6.0 to 7.5), anaerobic organotroph.     

The Terrestrial Silica Pump

Silicon (Si) cycling controls atmospheric CO₂ concentrations and thus, the global climate, through three well-recognized means: chemical weathering of mineral silicates, occlusion of carbon (C) to soil phytoliths, and the oceanic biological Si pump. In the latter, oceanic diatoms directly sequester 25.8 Gton C yr⁻¹, accounting for 43% of the total oceanic net primary production (NPP). However, another important link between C and Si cycling remains largely ignored, specifically the role of Si in terrestrial NPP. Here we show that 55% of terrestrial NPP (33 Gton C yr⁻¹) is due to active Si-accumulating vegetation, on par with the amount of C sequestered annually via marine diatoms. Our results suggest that similar to oceanic diatoms, the biological Si cycle of land plants also controls atmospheric CO₂ levels. In addition, we provide the first estimates of Si fixed in terrestrial vegetation by major global biome type, highlighting the ecosystems of most dynamic Si fixation. Projected global land use change will convert forests to agricultural lands, increasing the fixation of Si by land plants, and the magnitude of the terrestrial Si pump.     

The Oldest Caseid Synapsid from the Late Pennsylvanian of Kansas,and the Evolution of Herbivory in Terrestrial Vertebrates

The origin and early evolution of amniotes (fully terrestrial vertebrates) led to major changes in the structure and hierarchy of terrestrial ecosystems. The first appearance of herbivores played a pivotal role in this transformation. After an early bifurcation into Reptilia and Synapsida (including mammals) 315 Ma, synapsids dominated Paleozoic terrestrial vertebrate communities, with the herbivorous caseids representing the largest vertebrates on land. Eocasea martini gen. et sp. nov., a small carnivorous caseid from the Late Carboniferous, extends significantly the fossil record of Caseidae, and permits the first clade-based study of the origin and initial evolution of herbivory in terrestrial tetrapods. Our results demonstrate for the first time that large caseid herbivores evolved from small, non-herbivorous caseids. This pattern is mirrored by three other clades, documenting multiple, independent, but temporally staggered origins of herbivory and increase in body size among early terrestrial tetrapods, leading to patterns consistent with modern terrestrial ecosystem.     

The Importance of the Human Footprint in Shaping the Global Distribution of Terrestrial,Freshwater and Marine Invaders

Human activities such as transport, trade and tourism are likely to influence the spatial distribution of non-native species and yet, Species Distribution Models (SDMs) that aim to predict the future broad scale distribution of invaders often rely on environmental (e.g. climatic) information only. This study investigates if and to what extent do human activities that directly or indirectly influence nature (hereafter the human footprint) affect the global distribution of invasive species in terrestrial, freshwater and marine ecosystems. We selected 72 species including terrestrial plants, terrestrial animals, freshwater and marine invasive species of concern in a focus area located in NW Europe (encompassing Great Britain, France, The Netherlands and Belgium). Species Distribution Models were calibrated with the global occurrence of species and a set of high-resolution (9×9 km) environmental (e.g. topography, climate, geology) layers and human footprint proxies (e.g. the human influence index, population density, road proximity). Our analyses suggest that the global occurrence of a wide range of invaders is primarily limited by climate. Temperature tolerance was the most important factor and explained on average 42% of species distribution. Nevertheless, factors related to the human footprint explained a substantial amount (23% on average) of species distributions. When global models were projected into the focus area, spatial predictions integrating the human footprint featured the highest cumulative risk scores close to transport networks (proxy for invasion pathways) and in habitats with a high human influence index (proxy for propagule pressure). We conclude that human related information–currently available in the form of easily accessible maps and databases—should be routinely implemented into predictive frameworks to inform upon policies to prevent and manage invasions. Otherwise we might be seriously underestimating the species and areas under highest risk of future invasions.     

从超氧化物歧化酶的分布和结构看其分子进化

超氧化物歧化酶(SOD)是一种催化超氧化物阴离子自由基发生歧化反应, 生成氧和过氧化氢的金属酶. 按其结合的金属离子, 区分为Fe-SOD, Mn-SOD和CuZn-SOD三种. Fe-SOD主要存在于原核细胞中;Mn-SOD在原核和真核细胞中都存在;CuZn-SOD主要存在于真核细胞中. Fe, Mn-SOD的一级结构, 空间结构及其性质很相似, 来自一个共同的祖先; CuZn-SOD的结构与前两者相差较大, 是在以后的发展中单独进化的.     

陆生软体动物的分类系统

自Müller(1774)正式建立属,经过186年,Zilch(1959-1960)共归纳陆生软体动物有1091个属,其中,约有58.4%的属建立于1870～1929年间,以后逐渐减少。现估计全世界陆生软体动物有35000余种,主要包括腹足纲的前鳃亚纲和肺螺亚纲两大亚纲的种类,以肺螺亚纲柄眼目的种类最多,已知有30000余种。近年来,对于陆生软体动物的系统分类,有学者陆续发表了一些文章。目前有关腹足纲的分类和系统发育的研究,主要集中于石磺科Onchidiidae、复套蛞蝓科Veronicellidae、拉氏蛞蝓科Rathouisiidae三科,研究的重点在于如何确定它们的分类地位,它们是属于后鳃亚纲还是肺螺亚纲。关于琥珀螺科Succineidae的分类问题也有诸多研究。应用分子生物学和细胞生物学的方法对某些科属进行系统分类也是当今的热点。陆生软体动物的分类特征有:1.贝壳的形态与结构;2.颚片与齿舌;3.触角的形态及其位置、构造;4.生殖系统;5.排泄系统;6.神经系统;7.其他器官;8.细胞分类学和分子分类学。本文列出了现今常用的陆生贝类分类系统。     

The Evolution of Control and Distribution of Adaptive Mutations in a Metabolic Pathway

In an attempt to understand whether it should be expected that some genes tend to be used disproportionately often by natural selection, we investigated two related phenomena: the evolution of flux control among enzymes in a metabolic pathway and properties of adaptive substitutions in pathway enzymes. These two phenomena are related by the principle that adaptive substitutions should occur more frequently in enzymes with greater flux control. Predicting which enzymes will be preferentially involved in adaptive evolution thus requires an evolutionary theory of flux control. We investigated the evolution of enzyme control in metabolic pathways with two models of enzyme kinetics: metabolic control theory (MCT) and Michaelis–Menten saturation kinetics (SK). Our models generate two main predictions for pathways in which reactions are moderately to highly irreversible: (1) flux control will evolve to be highly unequal among enzymes in a pathway and (2) upstream enzymes evolve a greater control coefficient then those downstream. This results in upstream enzymes fixing the majority of beneficial mutations during adaptive evolution. Once the population has reached high fitness, the trend is reversed, with the majority of neutral/slightly deleterious mutations occurring in downstream enzymes. These patterns are the result of three factors (the first of these is unique to the MCT simulations while the other two seem to be general properties of the metabolic pathways): (1) the majority of randomly selected, starting combinations of enzyme kinetic rates generate pathways that possess greater control for the upstream enzymes compared to downstream enzymes; (2) selection against large pools of intermediate substrates tends to prevent majority control by downstream enzymes; and (3) equivalent mutations in enzyme kinetic rates have the greatest effect on flux for enzymes with high levels of flux control, and these enzymes will accumulate adaptive substitutions, strengthening their control. Prediction 1 is well supported by available data on control coefficients. Data for evaluating prediction 2 are sparse but not inconsistent with this prediction.THEORETICAL research on the process of adaptation has focused primarily on describing the size and number of genetic changes underlying phenotypic change (Fisher 1930; Kimura 1983; Orr 1998, 2002, 2003). By contrast, comparatively little theoretical attention has been given to the question of whether certain genes or types of genes are preferentially involved in the process of adaptation. Yet the current debate over the relative importance of regulatory vs. structural genes in morphological evolution (Hoekstra and Coyne 2007; Stern and Orgogozo 2008) clearly indicates that this question is of interest to evolutionary biologists.One situation in which this question is pertinent is the evolution of characters that are influenced by the concentration of end products of metabolic pathways. Often change in end-product concentration can be achieved by substitutions in any one of several genes in the pathway. One example is the intensity of floral pigmentation. To a first approximation, final pigment concentration, and hence color intensity, can be viewed as being determined by the flux rate down the pigment biosynthetic pathway for a fixed time corresponding to the duration of floral development. More generally, any situation in which flux rate determines phenotype is likely to fall in this category. In such situations, metabolic control theory (MCT) (Kacser and Burns 1973) and similar approaches (Heinrich and Rapoport 1974; Savageau 1976) indicate that changes in flux can be achieved by changing the activity of any enzyme in the pathway. We seek to determine whether and, if so, why enzymes differ in the probability that they contribute to evolutionary change in pathway flux.It has been suggested as a general principle that enzymes with the greatest control over flux will be disproportionately involved in such evolutionary change (Hartl et al. 1985; Eanes 1999; Watt and Dean 2000). This argument is based on the theoretical expectation that the probability of fixation of an advantageous allele is roughly proportional to its selection coefficient (Hedrick 2000). Since mutations equivalent in terms of enzyme kinetic properties will have greater effects on flux, and hence on fitness, in enzymes with greater metabolic control, mutations in those enzymes will be substituted preferentially.While this argument is likely sound, it simply pushes back the question of which genes evolve preferentially to the question of which enzymes are expected to have greatest control over flux. Although we are unaware of any theoretical attempts to model the evolution of flux control, many authors have speculated about where in pathways control is expected to be highest.Kacser and Burns (1973) hypothesized that the magnitudes of flux control exerted by different enzymes may be very similar. This hypothesis was based on the result from MCT that in linear pathways, overall flux control can be shared by all enzymes. Since metabolic pathways often consist of many enzymes, each would be expected to have only a limited potential to influence flux. Subsequent theoretical analysis of this hypothesis demonstrated that a given flux is consistent with many different flux-control distributions, including, at one extreme, equal flux control by all enzymes and, at the other extreme, major control by one or a few enzymes and little control for all others (Mazat et al. 1996). However, the question of which of these possibilities, if any, are likely to be favored by selection has not been addressed.Another hypothesis, the epistatic or synergistic principle, predicts that control will be vested in a single enzyme at any given time, but will shift over time among enzymes (Dykhuizen et al. 1987; Keightley 1989; Bost et al. 2001) According to this hypothesis, starting from equal control among enzymes in the pathway, selection to increase (or decrease) flux will cause the activity of one enzyme to increase (decrease). This change results in a decrease (increase) in flux control for the enzyme that changes and an increase (decrease) in control for the other pathway enzymes, causing control to be unequally shared. While this argument seems plausible, there has been no analysis of whether over time all enzymes have an equal chance of having elevated control.Finally, Eanes'' (1999) review of enzyme polymorphisms found that control is often centered in enzymes at pathway branch points, which constitute the most upstream enzymes of their specific branch. Flowers et al. (2007) also demonstrated that branching enzymes tend to exhibit more adaptive substitutions than downstream enzymes as would be expected under the principle that evolutionary change will be concentrated in enzymes with the largest control coefficients. In addition, evolutionary changes in these enzymes may be favored because they allow organisms to modify flux allocation to alternate functions and track environmental fluctuations. This suggestion is supported by the “branch point effect,” a theoretical demonstration that control coefficients can dramatically shift between enzymes depending on the kinetic rates of the two competing enzymes (LaPorte et al. 1984). However, this study does not address the question of how the distribution of control is likely to evolve, but describes only which distributions of control are mathematically possible. Thus, Eanes (1999, p. 318) concludes his review, stating “all enzymes in [a] contributing pathway may not be equal; determining the rule[s] for these inequalities should be a major goal in studies of enzyme polymorphism.”A control coefficient (CC) indicates the degree to which flux through a pathway is altered by a small change in the activity of an enzyme (see appendix; this is equivalent to the sensitivity coefficient of Kacser and Burns 1973). The “rules” governing the distribution of control coefficients are determined by the biological evolution of metabolic systems. While research demonstrates that there are many possible distributions of control coefficients, none has examined which of these is most likely to evolve. The optimization of metabolic systems has been explored in detail (Heinrich et al. 1991, 1997; Heinrich and Schuster 1998). In these studies, however, the investigators employ as optimization criteria maximizing flux, maximizing transient times, or minimizing metabolic intermediates, criteria whose biological and evolutionary relevance is unclear.In an effort to understand how control is expected to be shared among enzymes and predict which enzymes are most likely to contribute to adaptive genetic changes, we present two models of the evolution of flux control in a simple linear pathway. The first model employs the framework of MCT. Although there have been many challenges to the MCT framework (Savageau 1976, 1992; Cornish-Bowden 1989; Savageau and Sorribas 1989), it should be made clear that our aim is not to construct a precisely parameterized model of a particular biological system, but to use this generalized framework to address a single, critically ignored question: What are the rules governing how control will evolve to be distributed among enzymes? The use of the MCT framework to address questions in evolutionary genetics is firmly established, with investigation focused on the molecular basis of dominance (Kacser and Burns 1981; Keightley 1996a; Phadnis and Fry 2005; but see Bagheri and Wagner 2004), the relationship between metabolic flux and fitness (Dykhuizen et al. 1987; Szathmary 1993), the amount of additive and nonadditive genetic variance in metabolic systems (Keightley 1989), whether this variation can be explained by mutation–selection balance (Clark 1991), and patterns of response of quantitative traits to selection (Keightley 1996b). The second model we examine, saturation kinetics (SK), is based on Michealis–Menten kinetics and enables us to relax one major assumption of MCT: that enzymes are far from saturation.Here we limit our analysis to linear pathways as an initial attempt to examine these issues. We find that for such pathways control coefficients will generally evolve to be unequal; that the magnitude of this inequality depends on the thermodynamic properties, rather than the kinetic properties, of each reaction step; that upstream enzymes tend to evolve higher control coefficients than downstream enzymes; and that upstream enzymes fix advantageous mutations in greater numbers, and those mutations have larger effects than in downstream enzymes.     

山东长岛梨属植物资源分布及演化分析

为了探索我国梨属植物资源种类、分布及传播途径,本研究选择与陆地隔离的山东省长岛县为调查地域,对该地域梨属植物资源进行了实地调查和遗传分析。结果表明,长岛县梨属植物资源较为丰富,主要有杜梨、豆梨、沙梨等种类,变异类型较多,并发现一种特异类型;野生资源主要分布在山脊和半山腰,较为集中,且在小范围内能够发现多种资源类型。遗传分析结果显示,长岛梨属植物资源与邻近陆地资源关系较近。通过田间果实调查证实,鸟类吃食梨属植物,推定鸟类在梨属植物资源传播中可能充当一定的角色,这为进一步了解我国梨属植物的资源分布及演化提供了新的研究思路。     

栝楼属(葫芦科)植物的系统演化与地理分布

依据世界范围栝楼属植物种类的形态学、孢粉学、细胞学、系统发育研究资料,对栝楼属植物的系统演化和现代地理分布的形成进行了总结。栝楼组在栝楼属中处于原始地位,大苞组、叶苞组属于较进化类群,该属内的部分类群是在二倍体的水平上经过多倍化形成的。栝楼属在第三纪时期广布于欧洲、北美洲、亚洲、大洋洲,到第三纪晚期演化进程加快,南亚和中国西南山地逐步成为该属的起源中心与分化中心;受第四纪冰川期影响,该属在欧洲的种类逐渐消失,东亚成为该属的现代分布中心。栝楼属作为中国本地起源种,是中国植物区系中的重要组成部分。     

The Origin,Evolution and Distribution of Ligularia Cass. (Compositae)

The genus Ligularia Cass. is one of the large genera in Compositae-SenecioneaeTussilagininae. In subtrib. Tussilaginae, Ligularia is closely related to, but more advanced than, the genus Farfugium Lindl. It includes six sections, 11 series and 129 species. All the taxa are distributed in Asia with only two species extending to Europe. There are 119 species in E. Asia, Comprising 96 % of the world total. The highest concentration of species in E. Asia occurs in the Hengduan Mountains. In this area there are four section, six series and 67 species, of which 61 species are local endemics; thus 66% of sections, 54.5% of series and about 52 % of species in the world occur in this small area, indicating that it is a major distribution centre for Ligularia. According to character analysis, sect. Corymbosae ser. Calthifoliae with 5 species was considered as the most primitive group in this genus, which has reniform leaves, palmate veins, a few large capitula (arranging in Corymb-like inflorescence), and semispherical involucre etc. The primitive species, L. dentata and L. hodgsonii, are distributed from E. Sichuan to Japan via Hubei, Hunnan, Anhui, Fujian. This distribution pattern is consistent with that of its allied genus, Farfugium. According to the principle of common origin, the ancestors of the two genera appeared most probably in the same area. It was inferred that the area from E. Sichuan of China to Japan was the original area of the genus Ligularia, However, on the basis of geological history and the modern distribution of this genus, the author considers that central China with E. Sichuan might be the primary original area of Ligularia. Its dispersal route was mainly along the mountains of southern margin of Asia, with relatively few members dispersed northea stwards to NE. Asia. The origi-nal time of the genus Ligularia was at least not later than the middle Cretaceous.