Relation between population density and body size in stream communities

The existence of a general relation between population density and body size in animal assemblages has been debated because of known biases and ambiguities in the published data and data handling. Using new comprehensive data sets from two geographically separated stream communities that encompass 448 and 260 invertebrate taxa with a wide range of body sizes, we show that an inverse proportionality between density and body size is a consistent feature in these communities. The scaling across taxa is not statistically different between the two systems, indicating a convergent pattern of communities. Variation in the regression slope among different taxonomic groups indicates that these communities are not governed universally by a single ecological or energetic rule.     

Earthquake-caused coastal uplift and its effects on rocky intertidal kelp communities

The coastal uplift(approximately 40 to 60 centimeters) associated with the Chilean earthquake of 3 March 1985 caused extensive mortality of intertidal organisms at the Estación Costera de Investigaciones Marinas, Las Cruces. The kelp belt of the laminarian Lessonia nigrescens was particularly affected. Most of the primary space liberated at the upper border of this belt was invaded by species of barnacles, which showed an opportunistic colonization strategy. Drastic modifications in the environment such as coastal uplift, subsidence, or the effects of the El Ni?o phenomenon are characteristic of the southern Pacific. Modifications in the marine ecosystem that generate catastrophic and widespread mortalities of intertidal organisms can affect species composition, diversity, or local biogeography.     

Trophic control of production in a rocky intertidal community

In the low intertidal zone at Tatoosh Island, Washington, United States, minimal estimates of primary production can vary from 0 to an average of 86 kilograms of wet mass per square meter per year when the grazing assemblage is manipulated. Highly productive annual kelps (Laminariales) replace less productive perennial species when macroscopic grazers are reduced or absent, resulting in monodominant assemblages of Alaria marginata. Experiments were repeated in seven consecutive years. Increased species richness makes no significant additional contribution to annual production. Rather, a competitively superior species is favored when its enemies are reduced, suggesting that terrestrial perspectives on the role of biodiversity that are developed without considering consumers may not be general.     

Climate-related, long-term faunal changes in a california rocky intertidal community

Changes in the invertebrate fauna of a California rocky intertidal community between the period 1931 to 1933 and the period 1993 to 1994 indicate that species' ranges shifted northward, consistent with predictions of change associated with climate warming. Of 45 invertebrate species, the abundances of eight of nine southern species increased and the abundances of five of eight northern species decreased. No trend was evident for cosmopolitan species. Annual mean shoreline ocean temperatures at the site increased by 0.75 degrees C during the past 60 years, and mean summer maximum temperatures from 1983 to 1993 were 2.2 degrees C warmer than for the period 1921 to 1931.     

Catastrophic decline of a top carnivore in the gulf of california rocky intertidal zone

The predatory sun star, Heliaster kubiniji, once the commonest rocky intertidal asteroid of the Gulf of California, has been rare throughout this region since summer 1978 when a devastating disease outbreak occurred. This unprecedented phenomenon and several other exceptional ecological events in marine communities of the northeastern Pacific appear to be linked to large-scale climatic changes that occurred during 1977 and 1978. Implications of the decline in Heliaster kubiniji are discussed.     

Scaling stride frequency and gait to animal size: mice to horses

The stride frequency at which animals of different size change from one gait to another (walk, trot, gallop) changes in a regular manner with body mass. The speed at the transition from trot to gallop can be used as an equivalent speed for comparing animals of different size. This transition point occurs at lower speeds and higher stride frequencies in smaller animals. Plotting stride frequency at the trot-gallop transition point as a function of body mass in logarithmic coordinates yields a straight line.     

岩相潮间带大型底栖生物多样性对铜藻藻场的响应

2011年4月至2012年1月间,在南麂列岛火焜岙铜藻藻场和藻场外沿岸潮间带各设1条断面,对大型底栖生物的种类和数量组成、物种多样性和群落结构特点进行调查。共鉴定出底栖生物108种,其中,底栖动物93种,底栖藻类15种;藻场与藻场外沿岸高潮区和中潮区的软体动物、节肢动物、环节动物、其他动物和藻类的年均生物量和丰度均无显著差异;低潮区藻场沿岸藻类生物量大于藻场外沿岸,其他类群的年均生物量和丰度无显著差异。每个季节各潮区除春季低潮区藻场沿岸的藻类生物量大于藻场外沿岸外,其他均无显著差异。藻场沿岸潮间带的优势种为条纹隔贻贝,藻场外沿岸为条纹隔贻贝和棘刺牡蛎。藻场沿岸和藻场外沿岸潮间带大型底栖生物的Shannon-Wiener指数(H'),Pielou均匀度指数(J)和Margalef丰富度指数(d)无显著差异(P0.05)。非度量多维标度(MDS)和聚类分析表明,群落结构主要与季节有关,但在铜藻藻场生长旺盛期与藻场有关,说明铜藻生长旺盛期对其群落结构有一定的影响。     

三亚岩相潮间带底栖海藻群落结构及其季节变化

为了解三亚潮间带大型海藻生态现状,布设6条岩相断面,于2008年1-11月进行了四季野外的调查,并使用物种多样性指数与聚类分析研究了潮间带大型海藻四季的群落结构和多样性变化。调查共鉴定出大型底栖藻类130种,隶属于4门75属,其中红藻门41属67种、褐藻门16属31种、绿藻门15属29种、蓝藻门3属3种。潮间带海藻种类数季节变化不大,并呈低潮带>中潮带>高潮带的垂直分布特征,且中低潮带有共同分布种,夏季尤为普遍。潮间带海藻夏冬两季平均生物量高于春秋两季,但并无显著差异。优势种季节变化明显:春季有波利团扇藻 Padina boryana、日本仙菜Ceramium japonicum、半叶马尾藻Sargassum hemiphyllum、海柏Polyopes polyideoides,夏季有波状软凹藻Chondrophycus undulates、冠叶马尾藻Sargassum cristaefolium、宽扁叉节藻Amphiroa dilatata、石花菜Gelidium amansii,秋季有冠叶马尾藻、波状软凹藻、叶状铁钉菜Ishige foliacea,冬季有瓦氏马尾藻 Sargassum vachellianum、苔状鸭毛藻Symphyocladia marchantioides、珊瑚藻Corallina officinalis、波利团扇藻、日本仙菜。群落多样性冬高夏低:Shannon多样性和Margalef丰富度指数最大值出现在冬季,Shannon多样性和Pielou均匀度指数最低值出现在夏季。区域底栖藻类以暖水性热带-亚热带种为主,其次为温水性的暖温带种类,基本符合南海南区暖水区系特点。研究表明,尽管三亚潮间带底栖海藻种类数与生物量上并无显著的季节差异,但群落结构与多样性均显示出一定的季节变化。     

Scaling body support in mammals: limb posture and muscle mechanics

The scaling of bone and muscle geometry in mammals suggests that peak stresses (ratio of force to cross-sectional area) acting in these two support elements increase with increasing body size. Observations of stresses acting in the limb bones of different sized mammals during strenuous activity, however, indicate that peak bone stress is independent of size (maintaining a safety factor of between 2 and 4). It appears that similar peak bone stresses and muscle stresses in large and small mammals are achieved primarily by a size-dependent change in locomotor limb posture: small animals run with crouched postures, whereas larger species run more upright. By adopting an upright posture, large animals align their limbs more closely with the ground reaction force, substantially reducing the forces that their muscles must exert (proportional to body mass) and hence, the forces that their bones must resist, to counteract joint moments. This change in limb posture to maintain locomotor stresses within safe limits, however, likely limits the maneuverability and accelerative capability of large animals.     

种植密度、母本大小和移栽期对蔺草生长、开花及产量的影响

研究了蔺草(Juncus effusus L. var decipiens Bchen,品种:鄞蔺1号)生长、开花及产量对一些栽培措施的反应.结果表明,种植密度显著影响丛茎数(SPH)、草茎开花率(SFP)、长蔺率(LSP)、短草率(SSP)、生物学产量和经济产量,较高的种植密度使整个生育期SPH和产量显著高于低种植密度,但随着密度的增加,LSP显著下降.两种不同母本大小之间的SPH、SFP和产量没有显著差异,表明即使只有3枚草茎的移栽苗已具有感受环境因子时开花诱导的能力.随着移栽期的推迟,SFP显著增加,但对SPH、平均草茎长度(MSL)、LSP、SSP、生物学产量和经济产量没有显著影响.故建议,为减少草茎开花率,蔺草应在晚稻收割后尽早移栽.     

L-肉碱对圆型臂尾轮虫种群增长和个体大小的影响

【目的】探索L-肉碱对圆型臂尾轮虫(Brachionus rotundiformis)(简称轮虫)种群增长、怀卵率和个体大小的影响。【方法】用0.012 5mg/mL氯霉素作为轮虫培养液中的抑菌药物,1mg/L L-肉碱作为轮虫的营养强化剂,以正常培养条件下不添加L-肉碱和氯霉素的培养组为对照,分别设添加L-肉碱、氯霉素和L-肉碱+氯霉素处理,以纯酵母菌投喂培养轮虫5d。每天测定各组轮虫的种群密度、培养液中的细菌含量以及第5天时各组轮虫的背甲长、背甲宽。【结果】3~5dL-肉碱组的细菌含量均显著高于其他3组(P0.05);2~4d氯霉素组和L-肉碱+氯霉素组的细菌含量显著低于对照组(P0.05),但这两组之间的差异不显著(P0.05);第5天除L-肉碱组外其他3组之间细菌含量差异不显著(P0.05)。1~5d各处理组轮虫的种群密度均呈上升趋势,L-肉碱组轮虫的种群密度均高于其他3组。各组轮虫的怀卵率差异不显著(P0.05);添加氯霉素组轮虫的背甲长和背甲宽显著大于其他3组(P0.05)。【结论】L-肉碱对轮虫种群生长和繁殖的影响可能主要是通过影响细菌数量而起作用的。     

圈养尖吻蝮雌体大小、窝卵数和卵大小之间的关系

尖吻蝮(Deinagkistrodon acutus)野生资源日益枯竭,食用和药用压力巨大,亟需开展人工养殖.目前尖吻蝮的人工养殖技术还不够成熟,大多数养殖场采用半地下室饲养尖吻蝮,有关该条件下尖吻蝮的繁殖特性报道较少.为促进尖吻蝮的人工养殖,2010年4-9月,在湖南永州市对半地下室圈养的尖吻蝮成体的体型指标、窝卵数、窝卵重、卵重等繁殖特征之间的关系进行了研究.结果表明:圈养尖吻蝮成年雌体产单窝柔性卵,平均窝卵数为23.0±7.8(13-37)枚(n=23);将产后雌体体重和窝卵重相加记为产前雌体体重,采用SPSS 13.0软件处理数据,设置α=0.05和α=0.01,发现产前雌体体重分别与窝卵数、窝卵重、卵重均呈显著相关性;产前雌体体长分别与窝卵数、窝卵重、卵重无显著相关性;窝卵数与卵重无显著相关性,卵重分别与卵短径、卵长径均呈显著相关性.产前体重在1000-1200g之间的雌蛇所产窝卵数和单枚卵重的数值均较大且最集中,这保证了雌体繁殖输出后代的生存优势,对尖吻蝮人工养殖挑选雌性种蛇有一定的指导意义.     

水稻叶片形态、群体结构和产量对种植密度的响应

为了分析水稻叶片形态、群体结构和产量对种植密度的响应,以中籼稻高产选系JW10、JW103、JW113和JW34为材料,研究了不同种植密度[低密度(1 hm21.8×105穴)、中等密度(1 hm23.0×105穴)、高密度(1 hm24.2×105穴)]条件下水稻叶片形态、叶面积指数、叶面积垂直分布、光合速率、叶绿素荧光参数、干物质生产和产量形成的特点。结果表明,不同密度处理下,水稻叶片宽度及披垂度均发生了变化。中等密度处理下,齐穗期水稻上层叶面积比例高于低密度和高密度处理;中等密度处理下齐穗期水稻的光合速率和叶绿素荧光参数(Fv/Fm)居于低密度处理与高密度处理之间,但随齐穗后天数的增加,中等密度处理下水稻光合能力的优势逐渐增大。因此,在现有的生产条件和技术水平下,维持1 hm23.0×105穴的种植密度是水稻取得高产的基础。     

Virus population dynamics and acquired virus resistance in natural microbial communities

Viruses shape microbial community structure and function by altering the fitness of their hosts and by promoting genetic exchange. The complexity of most natural ecosystems has precluded detailed studies of virus-host interactions. We reconstructed virus and host bacterial and archaeal genome sequences from community genomic data from two natural acidophilic biofilms. Viruses were matched to their hosts by analyzing spacer sequences that occur among clustered regularly interspaced short palindromic repeats (CRISPRs) that are a hallmark of virus resistance. Virus population genomic analyses provided evidence that extensive recombination shuffles sequence motifs sufficiently to evade CRISPR spacers. Only the most recently acquired spacers match coexisting viruses, which suggests that community stability is achieved by rapid but compensatory shifts in host resistance levels and virus population structure.     

干旱区不同植物群落下土壤粒度特征研究

为探讨干旱区不同植物群落下土壤粒度特征,运用地统计学方法对艾比湖湿地7种不同植被下土壤粒度组成、分布特征及空间变异进行分析。结果表明:(1)除盐节木以极细砂为主、梭梭以细砂为主以外,其他均以粉砂为主;芦苇、梭梭和胡杨的土壤粒度为弱变异,碱蓬、盐节木、柽柳和黑果枸杞的土壤粒度为中等变异;除梭梭下土壤分选性较好外,其他植物群落下土壤分选性较差,偏度均属负偏,峰态为窄峰态。(2)碱蓬、芦苇、柽柳、盐节木和胡杨的土壤粒径均呈现为底层大于表层,黑果枸杞群落则相反,梭梭群落各层土壤颗粒的差异不大,样地土壤平均粒径具有强烈空间自相关性。(3)芦苇群落下土壤粒径与土壤盐分相关性较弱,碱蓬、盐节木、梭梭、柽柳、胡杨、黑果枸杞与盐分相关性较强,芦苇和黑果枸杞群落下土壤粒径与土壤含水量呈显著负相关,其他植物群落下土壤粒径与土壤含水量相关性不大。(4)艾比湖不同植物群落下土壤粒度变化受大风、季节性洪水、湖泊面积波动、土壤类型及成土母质等结构性因素的影响。     

高邮鸭体重、体尺和屠宰性能的测定及相关性分析

对成年高邮鸭的体重、体尺以及屠宰性能进行测定,并进行了相关性分析,结果表明,两性状间有23对呈显著正相关,31对呈极显著正相关,只有肝重与肌胃重呈极显著负相关.     

年龄、体重、体型及性别对健康犬骨量的影响

用钆－１５３双光子吸收法（ＤＰＡ）测定１２１只健康大、小型犬（其中大型犬７８只,小型犬４３只）的骨矿含量（ＢＭＣ）和骨密度（ＢＭＤ）。每只犬测量左右桡尺骨、肱骨、胫骨、股骨远端、腰椎（Ｌ－５或Ｌ－６,仅小型犬）、尾椎（Ｃ－７或Ｃ－８,仅大型犬）等１０个部位。结果表明,小型犬各部位骨量显著少于大型犬,两体型母犬骨量均比公犬低。经直线回归和多元回归分析,大、小型犬各部位骨量随年龄增长而下降,其中大型犬四肢骨量下降尤为明显。所有犬各部位骨量与体重呈显著正相关,小型犬每公斤体重的骨量增长率高于大型犬,两体型母犬骨量增长均低于公犬。结论：年龄、体重、体型和性别均是影响犬骨量的因素,其中体重和体型是主要因素,年龄对骨量亦产生一定作用。     

Fish in offshore kelp forests affect recruitment to intertidal barnacle populations

Kelp forests along the coast of central California harbor juvenile rockfish that prey on the larvae of invertebrates from the rocky intertidal zone. This predation reduces recruitment to barnacle populations to 1/50 of the level in the absence of fish. The dynamics of the intertidal community are thus strongly coupled to the dynamics of the offshore kelp community.     

藻种、贝类密度和大小对背角无齿蚌和河蚬摄食率的影响

在水温为(20±1)℃的室内实验条件下,研究铜绿微囊藻(Microcystis aeruginosa)、小球藻(Chlorella pyrenoidosa)、斜生栅藻(Scenedesmus obliquus)3种藻类和贝类规格(身体大小)及密度对背角无齿蚌(Anodonta woodiana)和河蚬(Corbicula fluminea)摄食率的影响。三因素方差分析表明:藻种对背角无齿蚌的摄食率无显著影响,但显著影响河蚬的摄食率;贝类密度和规格均显著影响2种贝类的摄食率,两者对背角无齿蚌摄食率有交互作用;但对河蚬无交互作用;2种贝类摄食率均随着密度的增加而下降,大规格背角无齿蚌和2种较低密度下的大规格河蚬的摄食率均分别显著小于小规格,但在2种较高密度下的河蚬摄食率在规格间无显著差异;2种贝类摄食率与水体溶解氧均显著正相关,但相关性河蚬明显高于背角无齿蚌;不同藻类的投喂对溶解氧不产生显著影响,但贝类大小和密度显著影响溶解氧。结果表明,溶解氧胁迫程度会影响身体大小和密度对2种贝类摄食率的交互作用,小规格河蚬对低溶解氧的耐受性低于大规格。