世界主要国家耕地动态变化及其影响因素

在世界人口持续攀升、全球耕地面积不断减少的背景下,探讨世界主要国家耕地变化其影响因素,对于分析预测未来世界耕地变化趋势、研究世界粮食安全具有积极意义。选择2050年人口过亿的17个国家和耕地面积排名前10的国家为研究对象,在分析1961—2007年耕地总量变化、人均耕地变化的基础上,探讨了耕地变化影响因素。研究结果表明,从20世纪60年代到2007年间的不同时期内,有越来越多的国家表现出耕地减少趋势,而人均耕地面积减少的国家个数高达90%以上。满足人口消费需求、城市化与经济发展是大多数国家耕地总量变化的主要动力;而人口快速增长、城市化则是导致许多国家人均耕地显著减少的重要原因。     

湖南丹霞地貌区的苔藓植物多样性

丹霞地貌是一种特殊的红层地貌,拥有独特的植被和植物区系组成。苔藓植物在丹霞地貌植被演替中具有重要的生态意义,但其基本的种类组成和分布却不清楚。通过野外考察和标本鉴定,共发现湖南丹霞地貌区苔藓植物53科96属174种(包括变种和亚种),其中苔类植物21科24属36种,藓类植物32科72属138种,其中台湾曲柄藓(Campylopus taiwanensis)、芒尖毛口藓(Trichostomum zanderi)、小火藓(Schlotheimia pungens)、中华细枝藓(Lindergiasinensis)、疏叶叶苔(Jungermannia laxifolia)和刺叶拟蒴囊苔(Saccogynidium irregularispinosum)等6种为中国特有种;铜绿净口藓(Gymnostomum aeruginosum)、稀枝钱苔(Riccia huebeneriana)、羽枝片叶苔(Riccardia multifida)等30个种为湖南新记录种。在174种中,稀有种为87种,如梨蒴珠藓(Bartramia pomiformis)、小火藓、毛枝藓(Pilotrichopsisdentata)等,这些种大多生态幅狭窄,对生境要求较苛刻,常见种(22种)和非常常见种(30种)共52种,多为生境广泛种或世界广布种,如地钱(Marchantia polymorpha)等。文中还提供了详细的湖南丹霞地貌苔藓名录及其凭证标本信息,并建议优先保护崀山无底洞和万佛山三十六湾两个苔藓丰富的小区。     

湖南丹霞地貌区蕨类植物多样性

丹霞地貌是有别于石灰岩地貌和花岗岩地貌的特殊地貌类型,发育着较为独特的植被类型和植物区系。我们于2007-2010年间对湖南新宁崀山、茶陵浣溪、平江石牛寨、资兴程江口、浏阳达浒、通道万佛山、沅陵五强溪夸父山、溆浦思蒙等地丹霞地貌的蕨类植物进行了广泛调查,报道了湖南丹霞地貌区蕨类植物31科66属183种的详细名录。其中,无腺姬蕨(Hypolepis polypodioides)、隐囊蕨(Notholaena hirsuta)、仙霞铁线蕨(Adiantum juxtapo-situm)、百山祖短肠蕨(Allantodia baishanzuensis)、肉质短肠蕨(A.succulenta)、骨碎补铁角蕨(Asplenium ritoense)、钝齿耳蕨(Polystichum deltodon var.henryi)、无盖耳蕨(P.gymnocarpium)、单羽耳蕨(P.simplicipinnum)、二型肋毛蕨(Ctenitis dingnanensis)等9种为湖南新记录种。湖南丹霞地貌的蕨类植物种类组成主要有鳞毛蕨科、蹄盖蕨科、水龙骨科、金星蕨科、卷柏科、铁角蕨科等较大科及鳞毛蕨属(Dryopteris)、卷柏属(Selaginella)、铁角蕨属(Asplenium)、短肠蕨属(Allantodia)和凤尾蕨属(Pteris)等较大属。生态适应特点分析表明丹霞地貌既有喜钙质土的种类,也有喜酸性土的种类,仙霞铁线蕨和无盖耳蕨可能是丹霞地貌的特有植物,因而具有石灰岩地貌蕨类植物区系和花岗岩地貌蕨类植物区系之间的过渡性特点。建议将垫状卷柏(Selaginella pulvinata)、福建观音座莲(Angiopterisfokiensis)、仙霞铁线蕨、骨碎补铁角蕨、鞭叶蕨(Cyrtomidictyum lepidocaulon)、无盖耳蕨等种类列为丹霞地貌蕨类植物中的优先保护种类,将通道万佛山三十六湾、湖南沅陵夸父山列为丹霞地貌蕨类植物的优先保护地区。     

Epidemiology in evolutionary time: the case of Wolbachia horizontal transmission between arthropod host species

Wolbachia are bacterial endosymbionts that manipulate the reproduction of their arthropod hosts. Although theory suggests that infections are frequently lost within host species due to the evolution of resistance, Wolbachia infect a huge number of species worldwide. This apparent paradox suggests that horizontal transmission between host species has been a key factor in shaping the global Wolbachia pandemic. Because Wolbachia infections are thus acquired and lost like any other infection, we use a standard epidemiological model to analyse Wolbachia horizontal transmission dynamics over evolutionary time. Conceptually modifying the model, we apply it not to transmission between individuals but between species. Because, on evolutionary timescales, infections spread frequently between closely related species and occasionally over large phylogenetic distances, we represent the set of host species as a small‐world network that satisfies both requirements. Our model reproduces the effect of basic epidemiological parameters, which demonstrates the validity of our approach. We find that the ratio between transmission rate and recovery rate is crucial for determining the proportion of infected species (incidence) and that, in a given host network, the incidence may still be increasing over evolutionary time. Our results also point to the importance of occasional transmission over long phylogenetic distances for the observed high incidence levels of Wolbachia. In conclusion, we are able to explain why Wolbachia are so abundant among arthropods, although selection for resistance within hosts often leads to infection loss. Furthermore, our unorthodox approach of using epidemiology in evolutionary time can be applied to all symbionts that use horizontal transmission to infect new hosts.     

Brassicaceae: Species checklist and database on CD-Rom

A species checklist has been prepared for the Brassicaceae (Cruciferae) family, providing the first updated list in over 70 years. The family, currently, includes 338 genera and 3709 species. The database contains approximately 14,000 taxonomic names (records). Taxon status and synonymy, taxon name, scientific authority, literature source and source verification, and the basionym are provided for each record. Electronic supplementary material to this article is available at and is accessible for authorized users.     

Similarity networks of protein binding sites

An increasing attention has been dedicated to the characterization of complex networks within the protein world. This work is reporting how we uncovered networked structures that reflected the structural similarities among protein binding sites. First, a 211 binding sites dataset has been compiled by removing the redundant proteins in the Protein Ligand Database (PLD) (http://www-mitchell.ch.cam.ac.uk/pld/). Using a clique detection algorithm we have performed all-against-all binding site comparisons among the 211 available ones. Within the set of nodes representing each binding site an edge was added whenever a pair of binding sites had a similarity higher than a threshold value. The generated similarity networks revealed that many nodes had few links and only few were highly connected, but due to the limited data available it was not possible to definitively prove a scale-free architecture. Within the same dataset, the binding site similarity networks were compared with the networks of sequence and fold similarity networks. In the protein world, indications were found that structure is better conserved than sequence, but on its own, sequence was better conserved than the subset of functional residues forming the binding site. Because a binding site is strongly linked with protein function, the identification of protein binding site similarity networks could accelerate the functional annotation of newly identified genes. In view of this we have discussed several potential applications of binding site similarity networks, such as the construction of novel binding site classification databases, as well as the implications for protein molecular design in general and computational chemogenomics in particular.     

Broadening the mission of an RNA enzyme

The “RNA World” hypothesis suggests that life developed from RNA enzymes termed ribozymes, which carry out reactions without assistance from proteins. Ribonuclease (RNase) P is one ribozyme that appears to have adapted these origins to modern cellular life by adding protein to the RNA core in order to broaden the potential functions. This RNA‐protein complex plays diverse roles in processing RNA, but its best‐understood reaction is pre‐tRNA maturation, resulting in mature 5' ends of tRNAs. The core catalytic activity resides in the RNA subunit of almost all RNase P enzymes but broader substrate tolerance is required for recognizing not only the diverse sequences of tRNAs, but also additional cellular RNA substrates. This broader substrate tolerance is provided by the addition of protein to the RNA core and allows RNase P to selectively recognize different RNAs, and possibly ribonucleoprotein (RNP) substrates. Thus, increased protein content correlated with evolution from bacteria to eukaryotes has further enhanced substrate potential enabling the enzyme to function in a complex cellular environment. J. Cell. Biochem. 108: 1244–1251, 2009. © 2009 Wiley‐Liss, Inc.     

中国多孔菌名录

本文中的多孔菌系指广义非褶菌目中具有孔状子实层体的种类,按照现代分类系统包括担子菌门中多孔菌目、锈革孔菌目、褐褶菌目、糙孢孔目、革菌目、糙孢革菌目和红菇目中孔状子实体的种类,还有伞菌目、阿太菌目、鸡油菌目和木耳目中个别属,如网孔菌属、胶孔菌属、榆孔菌属、牛排菌属和纵隔孔菌属等的种类。基于作者采集的1万余号标本和国内主要标本馆标本的研究,对中国多孔菌的种类进行了系统总结,目前有604种多孔菌发现于中国,多孔菌数量位居世界第一。对中国多孔菌的名称按新近研究成果和最新命名法规(维也纳法规)进行了订正。对121种新拟了汉语学名。     

Dimensions of global population projections: what do we know about future population trends and structures?

The total size of the world population is likely to increase from its current 7 billion to 8–10 billion by 2050. This uncertainty is because of unknown future fertility and mortality trends in different parts of the world. But the young age structure of the population and the fact that in much of Africa and Western Asia, fertility is still very high makes an increase by at least one more billion almost certain. Virtually, all the increase will happen in the developing world. For the second half of the century, population stabilization and the onset of a decline are likely. In addition to the future size of the population, its distribution by age, sex, level of educational attainment and place of residence are of specific importance for studying future food security. The paper provides a detailed discussion of different relevant dimensions in population projections and an evaluation of the methods and assumptions used in current global population projections and in particular those produced by the United Nations and by IIASA.