青海湖裸鲤寄生舌状绦虫的空间格局研究

舌状绦虫裂头蚴只寄生在体长小于２２０ｍｍ的青海湖裸鲤中,其种群在宿主种群中呈聚集分布。其聚集分布的强度随寄生虫种群平均密度的增加而降低。由于舌状绦虫在宿主体腔生长,产生明显的空间拥挤效应,可能导致宿主死亡或被食鱼鸟类捕食而转移到终末宿主中。在体长小于１２０ｍｍ的宿主中,密度依赖的死亡过程可能是使聚集强度降低的原因;而体长１４０－２００ｍｍ的鱼中,则是非密度依赖的全死过程使聚集强度增加．     

Analysis of sequence patterns proximal to the stop codons in Oryza sativa

Abstract

A comprehensive analysis of sequence patterns around the stop codons was performed, by using more than 26,000 rice full-length cDNA sequences. Here it is shown that the bias was most outstanding at the position immediately before the stop codons (?1 codon), where the AAC codon was strongly preferred among ANC codons. Compared with other positions, the codon immediately after the stop codons (+1 codon) also displayed an apparent difference, and had a strong consensus for base A at the first, C at the second, and A at the third letters, respectively. Notably, the base biases at the positions directly downstream of the stop codons, such as the +4, +5 and +6 positions, were much stronger than other positions in the 3′-UTR region, suggesting that those base positions might act as an extended stop signal in the process of protein synthesis. Examination of the relationship between sequence pattern and gene expression level, assessed by CAI values and EST counting, revealed a tendency towards bigger base biases for highly expressed genes. It could be inferred that the translation stop signal is possibly involved in many sequence recognition elements other than the stop codons; highly expressed genes should hold strong sequence consensus around the stop codons for efficient translation termination.     

黄河口岸线变迁对潮滩盐沼景观格局变化的影响

基于2001、2005和2010年3期TM遥感影像,运用GIS技术,分析了黄河三角洲不同区士或(Ⅰ区,刁口段;Ⅱ区,东营港及临近岸段;Ⅲ区,河口段;Ⅳ区,南部莱州湾岸段)潮滩盐沼的景观演变与海岸线变迁的动因关系。结果表明,岸线变迁直接决定了潮滩盐沼面积的增长或缩减,但其在不同区域的影响程度差异较大。2001-2010年,Ⅰ区由于1976年以后刁口流路废弃、水沙输入量锐减导致其岸线持续蚀退,潮滩面积锐减明显(减少57.64 km~2,减少率25.94%);Ⅲ区由于1976年以后黄河由清水沟或清8汉入海,河口区域的持续淤积状态使得岸线持续增长,潮滩面积增加显著(增加66.17 km~2,增长率17.39%);而Ⅱ区由于海堤修建及港口建设等人类活动影响,岸线基本处于稳定状态,潮滩面积变化不大,Ⅳ区潮滩面积持续增加。不同区域潮滩盐沼景观格局随距海远近均呈明显带状分布,依次为芦苇盐沼、碱蓬-柽柳-芦苇盐沼、碱蓬盐沼和光滩。2001-2010年,不同景观类型之间存在明显转移,光滩、碱蓬盐沼和芦苇盐沼的面积持续减少(分别减少6.02、18.39和99.20 km~2,减少率为4.61%、12.86%和50.11%),碱蓬-柽柳-芦苇盐沼的面积整体呈增加趋势(增加35.50 km~2,增长率为24.99%)。研究发现,不同区域的景观类型均随岸线的淤积或蚀退而发生向海或向陆的演替,岸线变迁是影响不同区域潮滩盐沼景观格局的决定因素,而黄河调水调沙工程的长期实施对于近年来河口段岸线的变迁以及盐沼植被景观类型的演变具有深刻影响。     

五种荒漠灌木群落土壤有机碳垂直分布及其与根系分布的关系

研究土壤有机碳与根系分布之间关系对评估碳储量和固碳潜力具有重要意义,而我国荒漠区灌木群落土壤有机碳与植物根系之间的关系尚不清楚。本研究选取深根性表层型灌木(表层根系生物量最大)梭梭(Haloxylon ammodendro)和中间锦鸡儿(Caragana intermedia)、深根性非表层型(表层根系生物量不是最大)灌木白刺(Nitratia tangutorum)、浅根性表层型灌木红砂(Reaumuria songarica)及浅根性非表层型灌木霸王(Sarcozygium xanthoxylon)为优势种的5种荒漠灌木群落为研究对象,测定100 cm深度内不同层次根系生物量及土壤有机碳含量,探讨灌木群落土壤有机碳的垂直分布格局及其与根系之间的关系。结果显示:(1)0~100 cm土壤有机碳密度与群落0~20 cm根系生物量碳密度显著正相关,与其他层次或累积深度不显著相关;(2)梭梭群落0~100 cm土壤有机碳密度显著低于与其他4个群落(P0.01),其他4个群落无显著差异(P0.05);(3)优势种为表层型的梭梭、中间锦鸡儿和红砂群落土壤有机碳密度与群落及优势种根系变化趋势一致,优势种为浅根性非表层型的霸王群落仅表层40 cm土壤有机碳与优势种灌木根系分布规律一致,优势种为深根性非表层型的白刺群落土壤有机碳与优势种根系分布规律一致。本研究表明,荒漠灌木群落0~100 cm土壤有机碳储量与群落0~20 cm根系生物量显著相关,群落优势种根系分布类型是影响土壤有机碳垂直分布格局的重要因素。     

林睡鼠幼鼠的活动规律和行为初步观察

本文通过红外线照相的方法,对发育期的林睡鼠幼鼠进行室内活动规律及行为观察,为充分了解林睡鼠越冬前的能量储备形式提供饲养参考。将鼠密度监测仪固定在饲养笼具上方,24h连续拍照,采集和分析6-9月年龄在10周内的幼鼠各种活动数据。结果显示：幼鼠一天中超过70%的时间都在窝内度过,大部分时间都蜷缩成一团少有动作;在窝外活动时间多在玩耍,如攀爬笼架。用于进食和饮水的时间不超过全天的2%。林睡鼠幼鼠主要活动时间在21:00-07:00,活动高峰在21:00-03:00之间。幼鼠出生3周后开始出窝活动,哺乳期30d后开始采食,5周后幼鼠有交配玩耍行为。随着日龄的增长,活动高峰从23：00提前到21：00,活动时间也逐渐延长,但9周龄后活动时间逐渐缩短,幼鼠的饮水进食时间与其活动的时间长短较为一致。10周体重可达成年体重的70%。研究表明,林睡鼠在夏秋季节基本是昼伏夜出动物。光照是影响其在外活动的重要因素之一。幼鼠6周后所需的饲料和水量大于成年林睡鼠,在此期间要注意饲料和水的补充。     

海南岛甘什岭热带低地雨林棕榈藤空间点格局分析

以海南岛甘什岭热带低地雨林白藤(Calamus tetradactylus)、大白藤(C.faberii)、华南省藤(C.rhabdocladus)、黄藤(Daemonorops margaritae)和小钩叶藤(Plectocomia microstachys)5种棕榈藤种群为研究对象,采用点格局分析方法对棕榈藤种内和种间空间分布格局及相互关系进行分析。结果表明:(1)海南岛甘什岭热带低地雨林棕榈藤种群的空间格局与空间尺度有着密切的关系,在小尺度上,5种棕榈藤种群都更倾向于聚集分布,随着尺度的增长,各棕榈藤种群主要趋向于随机分布,形成不同的空间分布格局。(2)各藤种间的空间关联情况在整体尺度上表现出明显负关联的是白藤和黄藤、白藤和大白藤,这可能是因为它们对生存空间及养分的需求相同或相似,存在明显的竞争关系。(3)华南省藤和大白藤在整体尺度上表现出明显正关联,这可能是由于它们在生长过程中相互庇护,用于抵御动物捕食和热带雨林内多变的外部环境。(4)黄藤和小钩叶藤以及白藤和小钩叶藤呈现出明显不相关,这说明它们对环境和生存空间的依赖没有冲突性,能做到和平共存。     

Models of central pattern generators for quadruped locomotion I. Primary gaits

In this paper we continue the analysis of a network of symmetrically coupled cells modeling central pattern generators for quadruped locomotion proposed by Golubitsky, Stewart, Buono, and Collins. By a cell we mean a system of ordinary differential equations and by a coupled cell system we mean a network of identical cells with coupling terms. We have three main results in this paper. First, we show that the proposed network is the simplest one modeling the common quadruped gaits of walk, trot, and pace. In doing so we prove a general theorem classifying spatio-temporal symmetries of periodic solutions to equivariant systems of differential equations. We also specialize this theorem to coupled cell systems. Second, this paper focuses on primary gaits; that is, gaits that are modeled by output signals from the central pattern generator where each cell emits the same waveform along with exact phase shifts between cells. Our previous work showed that the network is capable of producing six primary gaits. Here, we show that under mild assumptions on the cells and the coupling of the network, primary gaits can be produced from Hopf bifurcation by varying only coupling strengths of the network. Third, we discuss the stability of primary gaits and exhibit these solutions by performing numerical simulations using the dimensionless Morris-Lecar equations for the cell dynamics.     

The evolution and genetics of sexually dimorphic ‘dual’ mimicry in the butterfly Elymnias hypermnestra

Sexual dimorphism is a major component of morphological variation across the tree of life, but the mechanisms underlying phenotypic differences between sexes of a single species are poorly understood. We examined the population genomics and biogeography of the common palmfly Elymnias hypermnestra, a dual mimic in which female wing colour patterns are either dark brown (melanic) or bright orange, mimicking toxic Euploea and Danaus species, respectively. As males always have a melanic wing colour pattern, this makes E. hypermnestra a fascinating model organism in which populations vary in sexual dimorphism. Population structure analysis revealed that there were three genetically distinct E. hypermnestra populations, which we further validated by creating a phylogenomic species tree and inferring historical barriers to gene flow. This species tree demonstrated that multiple lineages with orange females do not form a monophyletic group, and the same is true of clades with melanic females. We identified two single nucleotide polymorphisms (SNPs) near the colour patterning gene WntA that were significantly associated with the female colour pattern polymorphism, suggesting that this gene affects sexual dimorphism. Given WntA''s role in colour patterning across Nymphalidae, E. hypermnestra females demonstrate the repeatability of the evolution of sexual dimorphism.     

Storage-protein variation in wild emmer (Triticum turgidum ssp.dicoccoides) from Jordan and Turkey.

Genetic diversity in the seed storage-proteins encoded at theGlu-A1,Glu-B1 andGli-B1/Glu-B3 loci was studied electrophoretically in 315 individuals belonging to nine populations ofT. dicoccoides from Jordan and three from Turkey. The inter- and intra-population distribution of seed storage-protein alleles at the considered loci and its link with geographical factors were investigated. Population differentiation in seed storage-proteins was in some cases very high with very weak correlations with geographic distance. Greater gene differentiation was found within and between populations which were geographically very close in Jordan than between those from Jordan and Turkey. However the distribution of alleles appeared to be non random. Samples collected from populations at locations over 900 m above sea level were less polymorphic than those collected at lower altitudes (500–700 m), whereas the relative genetic differentiation between populations was greater between those collected at higher altitudes. Seed storage-protein differentiation was significantly correlated with the altitude of the collecting sites. Although it is difficult to point out the selective pressure of altitude per se, altitude can reflect an integration of several environmental parameters. The possible adaptive value of seed storage-proteins is discussed.     

The fecundity patterns of S and L type rotifers of Brachionus plicatilis

Fecundity patterns of S and L type rotifers Brachionus plicatilis, which were previously found to have distinct growth ability, were analyzed using data of age-specific fecundity. The data were obtained by individual cultures of S and L type strains at 17, 24 and 34 °C. The pattern was analyzed by using normal probability functions. When the age was transformed into logarithmic value, the S and L types had an identical pattern of fecundity at every temperature. This fact indicates that the difference of the growth response to the temperature between S and L type strains stemmed only from the differences in net reproduction rate, not from the pattern.