雌核发育团头鲂的形态和遗传特征分析

利用团头鲂(Megalobrama amblycephala)正常二倍体群体作为对照组, 对团头鲂减数分裂雌核发育二倍体群体的形态特征、染色体组型、性腺发育及遗传特征进行了分析. 结果表明: 雌核发育群体与正常群体在外部可数、可量性状上没有显著性差异(P0.05); 但雌核发育群体出现了尾鳍条数为12的畸形个体, 与正常个体之间有较大的差异; 两个群体的染色体条数都是48, 核型均为18 m+26 sm+4 st; 观察了20尾雌核发育个体的性腺, 均为雌性个体且卵巢发育良好; 采用10个微卫星标记对2个群体的遗传多样性分析, 结果表明正常群体和雌核发育群体平均等位基因数分别为3.8个和1.7个, 雌核发育群体的多态性显著低于正常群体, 表明减数分裂雌核发育二倍体具有高度的遗传相似性, 可作为一个很好的育种材料.       

Morphological traits determine the winner of “symmetric” fights in hermit crabs

This study aimed at investigating in the hermit crab Pagurus longicarpus whether some morphological traits and their slight variations might determine the winner of a contest in symmetric pairs, i.e. pairs composed of individuals matched by their overall size. In the pre-experimental phase, 400 crabs were individually kept in isolation for a week to eliminate the effects of their previous social experiences and were allowed to enter adequate shells to equalize their motivation to fight. Then, we formed 200 pairs matched for shell and body size and observed their agonistic behaviour for 15 min. Alphas (and betas) were deemed as those individuals that won more than half of the recorded fights. Finally, crabs were sacrificed and sexed, and 6 and 8 measures were taken of their shells and bodies, respectively. Raw data were converted to compositional data and subjected to an isometric log-ratio transformation prior to statistical analysis. Alphas were found to occupy heavier and wider shells than betas, both characteristics that, together with the correlated high level of encrustation, make the apparent dimension of the crab larger and thus favour that individual during agonistic encounters. As expected, hermit crabs were sexually dimorphic in their chelae, but sexes differed also in the length of the dactylus of their third walking leg and in their body weight. Alphas were heavier than betas and had longer propodi and wider dactyli on the third walking legs than betas. The latter character might be advantageous during shell fights when the walking legs of the attacker are used to hold the defender's shell in the spasmodic shaking and their wider dactyli might assure a firmer seizing of it. Indeed, a correct execution of this pattern allows for the eviction of the defender. Our results suggest that more attention towards variations in morphological traits other than body size might improve our understanding of the factors that affect individual Resource Holding Power and fight dynamics.     

Occurrences of harmful algal blooms (HABs) associated with ocean environments in the South China Sea

Harmful algal blooms (HABs) occur frequently in the South China Sea (SCS), causing enormous economic losses in aquaculture. We analyzed historical HAB records during the period from 1980 to 2003 in SCS. We found that HABs-affected areas have expanded and the frequency of HABs varied during this period. The seasonal and annual variations, as well as causative algal species of HABs are different among the four regions. Areas with frequent HABs include the Pearl River Estuary (China), the Manila Bay (the Philippines), the Masinloc Bay (the Philippines), and the western coast of Sabah (Malaysia). HABs occurred frequently during March–May in the northern region of SCS, May–July in the eastern region, July in the western region, and year-round in the southern region. Among the species that cause HABs, Noctiluca scintillans dominated in the northern region, and Pyrodinium bahamense in the southern and eastern regions. Causative species also varied in different years for the entire SCS. Both P. bahamense and N. scintillans were the dominant species during 1980–2003. Some species not previously recorded formed blooms during 1991–2003, including Phaeocystis globosa, Scrippsiella trochoidea, Heterosigma akashiwo, and Mesodinium rubrum. Variations in HABs are related to various regional conditions, such as a reversed monsoon wind in the entire SCS, river discharges in the northern area, upwelling in Vietnam coastal waters during southwest winds and near Malaysia coastal waters during northeast winds, and eutrophication from coastal aquaculture in the Pearl River estuary, Manila Bay, and Masinloc Bay. Handling editor: D. Hamilton     

An inventory of continental U.S. terrestrial candidate ecological restoration areas based on landscape context

Landscape context is an important factor in restoration ecology, but the use of landscape context for site prioritization has not been as fully developed. We used morphological image processing to identify candidate ecological restoration areas based on their proximity to existing natural vegetation. We identified 1,102,720 candidate ecological restoration areas across the continental United States. Candidate ecological restoration areas were concentrated in the Great Plains and eastern United States. We populated the database of candidate ecological restoration areas with 17 attributes related to site content and context, including factors such as soil fertility and roads (site content), and number and area of potentially conjoined vegetated regions (site context) to facilitate its use for site prioritization. We demonstrate the utility of the database in the state of North Carolina, U.S.A. for a restoration objective related to restoration of water quality (mandated by the U.S. Clean Water Act), wetlands, and forest. The database will be made publicly available on the U.S. Environmental Protection Agency's EnviroAtlas website ( http://enviroatlas.epa.gov ) for stakeholders interested in ecological restoration.     

Establishment of a 4650-year-long eigenvalue chronology based on tree-ring cores from Qilian junipers (Juniperus przewalskii Kom.) in Western China

This paper describes a tree-ring width chronology that spans the past 4650 years, established using the recently developed eigenanalysis technique. The aim is to show whether this eigenanalysis method enables the extraction of long-term tree-growth variations that are due to climatic changes, from a large dataset comprising 1263 tree-ring width records sampled from the highlands of Western China. In order to exclude the so-called growth rate/life span association effect, tree-ring width records were sorted into six subsets, based on the life spans of the trees sampled: 200–400, 400–600, 600–800, 800–1000, 1000–1500 years old, and trees older than 1500 years. Some partial chronologies were created, by pairing the set of all tree samples (living, dead, archaeological remains) with the living trees belonging to each subset. We computed the contours of tree-growth variations (on both 100-year and longer time scales) for each subset, ending with six pairs of these partial subset chronologies. Two sums of all these partial chronologies thus yielded a record of precipitation variations over a period ranging from 2627 BCE up to 2012 CE. It was found that this record shows a high degree of similarity to the existing chronology produced using the regional curve standardization (RCS) method applied to the same dataset, indicating that the eigenvalue chronology is capable of faithfully extracting long-term climatic variations. This also confirms that the first eigenvector represents the growth pattern that is characteristic of each biologically unique tree as well as the micro-environment of each tree stand. The variations observed over the last millennium seem to be connected to a cycle of solar activity with a period of ∼200 years. However, a clear lack of correspondence between solar activity and tree growth prior to 1000 CE indicates that the recent consistency may be coincidental. We believe that the eigenanalysis technique is readily applicable to other kinds of tree-ring datasets from different parts of the world.     

Morphological and molecular characterization of populations of plains bristlegrass (<i>Setaria macrostachya</i> Kunth) in Chihuahua,México

Plains bristlegrass (Setaria macrostachya Kunth) is a native grass with forage value. However, due to the lack of grazing management practices, populations and thus genetic diversity, have been reduced. Morphological and genetic variability were analyzed on 44 populations of plains bristlegrass in the State of Chihuahua. Plants were transplanted in a common area under natural conditions. Two years later, morphological characterization was evaluated measuring nine variables, and genetic variability using AFLP molecular markers. The principal components analysis (PC) showed that the three first principal components explained 73.74% of the variation. The variables with the greatest contribution to the variance in PC1 were plant height and inflorescence length; in CP2, tiller number and leaf width; and in PC3, tiller thickness. Application of four pairs of primers, presented 186 total bands, from which 87.10% showed polymorphism and 12.90% monomorphism. The combination of EcoRI-AGG MseI-CAG primers detected the highest percentage (93%) of polymorphism with 40 polymorphic bands. The cluster analysis and Dice coefficient indicated that populations clump into two groups. The wide genetic variability and morphological characteristics detected among populations represent the basis for the selection of populations that could be used with different purposes in the rehabilitation of ecosystems. In addition, this study will allow establishment of in situ conservation strategies.     

中国淡水水体常见束丝藻种类的形态及生理特性研究

束丝藻(Aphanizomenon Morr. ex Born. et Flah)是我国水华蓝藻的重要种类, 由其产生的束丝藻水华已经引起了许多的环境问题。水华束丝藻、柔细束丝藻和依沙束丝藻是我国淡水水体常见的三种束丝藻种类,然而, 国内外对它们的生理学研究却相对较少。基此, 文章对水华束丝藻、柔细束丝藻和依沙束丝藻的形态特性、色素含量、生长及光合作用进行了比较研究, 结果表明丝状体的营养细胞、异形胞和厚壁孢子的长宽比具有一定的差异性, 揭示了厚壁孢子的长宽比可作为三种束丝藻分类的一个参数; 同时, 种间的差异性也体现在三种束丝藻的生理特性上, 相比水华束丝藻和依沙束丝藻, 柔细束丝藻的藻蓝素含量较高, 而叶绿素a、类胡萝卜素含量、最大光合作用(Pm)、表观光合作用效率(α)和最大电子传递速率(ETRmax)显著偏低。此外, 水华束丝藻和依沙束丝藻生理特性基本一致, 表明了形态不同的三种束丝藻在生理上可被分为两种类型, 暗示了依沙束丝藻可能具有像水华束丝藻一样形成水华的生理潜能且由于它的产毒性所以应该倍加关注       

杭州湾滨海湿地3种草本植物叶片N、P化学计量学的季节变化

动态平衡理论是生态化学计量学的理论基础, 各种有机体是否存在一个固定的化学计量比是生态学研究的热点问题。该文研究了杭州湾滨海湿地3种优势物种海三棱藨草(Scirpus mariqueter)、糙叶薹草(Carex scabrifolia)和芦苇(Phragmites australis)叶片N、P生态化学计量特征的季节变化。结果发现, 3种植物叶片N含量范围分别是7.41-17.12、7.47-13.15和6.03-18.09 mg·g^-1, 平均值(±标准差)分别为(11.69 ± 2.66)、(10.17 ± 1.53)和(11.56 ± 3.19) mg·g^-1; 叶片P范围分别是0.34-2.60、0.41-1.10和0.35-2.04 mg·g^-1, 平均值为(0.93 ± 0.62)、(0.74 ± 0.23)和(0.82 ± 0.53) mg·g^-1; N:P范围分别是7.19-30.63、11.58-16.81和8.62-21.86, 平均值为16.83 ± 8.31、14.53 ± 3.91和16.49 ± 5.51, 可见不同植物其生态化学计量值范围存在一定差异, 但经方差分析发现3种草本植物间生长季节内N、P元素含量差异并不显著(p > 0.05)。各物种叶片N、P含量均表现出在生长初期显著大于其他生长季节(p < 0.05), 生长旺季(6、7月)随着叶片生物量的持续增加, N、P含量逐渐降低并达到最小值, 随后8-9月叶片不再生长而N、P含量逐渐回升, 在10月叶片衰老时N、P含量再次下降; 叶片N:P则在生长初期较小, 在生长旺季先升高后降低, 随后叶片成熟不再生长时又逐渐增加并趋于稳定。     

东亚飞蝗行为和形态型变的判定指标

通过田间、室外罩笼、室内行为测试等一系列实验,研究了东亚飞蝗群居型和散居型之间的行为和形态差异。确立了东亚飞蝗不同生态型个体的形态和行为指标．结果表明,雌雄散居型蝗蝻每分钟的跳跃次数均在1．4以下,转向次数分别在1．3和1．4以下;雌雄群居型蝗蝻每分钟的跳跃次数均在1．6以上,转向次数分别在1．6和1．5以上．群居型蝗虫的跳跃次数、转向次数显著高于散居型蝗虫。所以跳跃次数、转向次数可作为东亚飞蝗行为型变判定指标．在同型不同性别的蝗虫之间行为型变指标没有显著差异．F／C值可作为4龄以上东亚飞蝗的形态型变判定指标。而E／F值可作为东亚飞蝗成虫的形态型变判定指标．两型的F／C值都随龄期的增长而增加,且同龄期雄虫F／C均大于雌虫F／C．F／C、E／F值在不同型态和同型不同性别间均存在极显著差异．因此,确定两型形态型变标准时应将雌、雄虫分开,即雌性和雄性散居型第4、5龄及成虫的F／C值分别大于2．5、2．8、3．3和2．6、2．9、3．5;雌性和雄性群居型第4、5龄及成虫的F／C值分别小于2．5、2．7、3．1和2．5、2．8、3．3．成虫的E／F值也可以作为成蝗形态型变的判断指标．     

岷江上游干旱河谷海拔梯度上白刺花叶片生态解剖特征研究

对岷江上游干旱河谷海拔梯度上（1 650～1 950 m）白刺花(Sophora davidii)叶片进行生态解剖学研究.观测指标包括叶片形态特征（叶长宽比、叶面积、叶片厚度）、解剖结构（表皮厚度、栅栏组织厚度(P)、海绵组织厚度(S)、P/S比值、表皮角质膜厚度）及叶表皮特征（气孔器密度和面积、表皮细胞密度和面积、表皮毛密度和长度）.结果表明,白刺花叶片面积为0.144～0.208 cm²,叶总厚度为171.58～195.83 μm;叶肉组织分化明显,栅栏组织厚度与海绵组织厚度分别为69.83～82.42和62.00～ 80.67 μm,P/S的比值为1.14～1.01,上下表皮厚度分别为14.03～15.33和13.88～16.17 μm,上下角质膜厚度分别为2.66～4.56和2.76～2.02 μm;气孔密度为13.71～15.02个·mm^-2,其面积为249.86～280.43 μm²;表皮细胞密度为160.54～178.43个·mm^-2,其面积为557.43～626.85 μm²;表皮毛长度为186.51～260.99 μm,其密度为18.29～32.27个·mm^-2.随海拔升高叶面积、叶厚度、栅栏组织和海绵组织的厚度、气孔器面积、表皮细胞面积以及表皮毛密度呈增加趋势,而角质膜厚度、表皮细胞密度和表皮毛长度则呈减小趋势;叶长宽比、P/S的比值、表皮厚度与气孔器密度无明显差异.