Significance and importance: some common misapprehensions about statistics

There are many common misapprehensions about statistics that occur in the literature. We are sure that the three misapprehensions we deal with in this short review are widespread. They concern:

• 1) what P values mean;
• 2) what an insignificant result means, and what it does not mean; the question of the ‘power’ of a statistical test;
• 3) the difference between importance and statistical significance.

We produce no formulae or recipes for dealing with particular situations, instead we concentrate on the commonsense use of simple statistics. We emphasise that if the use of any but the simplest statistics is intended, it is much better to get proper statistical help before starting experiments, rather than afterwards. Copyright © 2009 John Wiley & Sons, Ltd.     

Mineral nutrient economy in competing species of Sphagnum mosses

Bog vegetation, which is dominated by Sphagnum mosses, depends exclusively on aerial deposition of mineral nutrients. We studied how the main mineral nutrients are distributed between intracellular and extracellular exchangeable fractions and along the vertical physiological gradient of shoot age in seven Sphagnum species occupying contrasting bog microhabitats. While the Sphagnum exchangeable cation content decreased generally in the order Ca²⁺ ≥ K⁺, Na⁺, Mg²⁺ > Al³⁺ > NH₄ ⁺, intracellular element content decreased in the order N > K > Na, Mg, P, Ca, Al. Calcium occurred mainly in the exchangeable form while Mg, Na and particularly K, Al and N occurred inside cells. Hummock species with a higher cation exchange capacity (CEC) accumulated more exchangeable Ca²⁺, while the hollow species with a lower CEC accumulated more exchangeable Na⁺, particularly in dead shoot segments. Intracellular N and P, but not metallic elements, were consistently lower in dead shoot segments, indicating the possibility of N and P reutilization from senescing segments. The greatest variation in tissue nutrient content and distribution was between species from contrasting microhabitats. The greatest variation within microhabitats was between the dissimilar species S. angustifolium and S. magellanicum. The latter species had the intracellular N content about 40% lower than other species, including even this species when grown alone. This indicates unequal competition for N, which can lead to outcompeting of S. magellanicum from mixed patches. We assume that efficient cation exchange enables Sphagnum vegetation to retain immediately the cationic nutrients from rainwater. This may represent an important mechanism of temporal extension of mineral nutrient availability to subsequent slow intracellular nutrient uptake.     

Functional and adaptive significance of differentially expressed lactate dehydrogenase isoenzymes in tissues of four obligatory air-breathing Channa species

This study investigates the differential expression of lactate dehydrogenase (LDH) isoenzymes in the genus Channa using PAGE. With the help of obligate air-breathing, all of the selected species can sustain water deprivation to varying degrees. In subunit composition and higher electrophoretic mobility of LDH-A₄, the profiles of channid species were similar to other teleosts documented in the literature. However, inter- and intra-species differences, with particular reference to aerobic/anaerobic metabolic options, existed. Whereas glycolysis in Channa punctata appears to depend largely on aerobic LDH-B and partly on anaerobic LDH-A, metabolism in C. gachua, C. striata and C. marulius depends exclusively on the activity of anaerobic LDH-A. Expression of the third locus Ldh-C was recorded in the eyes of C. marulius, in addition to C. gachua. Heat inactivation experiments reveal species differences between LDH isoenzymes and a general order of the relative stabilities: LDH-C > DH-B > LDH-A. Metabolic and evolutionary implications of the findings have also been discussed.     

柃属植物叶宏观结构及其分类学意义

为了探讨柃属植物属下等级的系统演化路线及一些种的具体分类学地位,采用脉络法对国产柃属植物34种1变种进行了叶宏观结构比较研究,结果显示柃属植物脉序类型皆为环节曲行羽状脉,一级脉表现为较高的一致性,二级脉与一级脉的夹角为锐角或近直角,二级间脉为简单型或复合型,三级脉多为结网型,叶缘末级脉序结环或不完全,网眼的形状和大小不规则,发育不完全或不完善;这些特征存在种间差异,可用于类群的比较和鉴别。研究同时采用UPGMA法对所选16个叶宏观结构性状进行聚类分析,根据系统树的5个分支,讨论了柃属植物叶的基本演化路线。研究证明叶宏观结构特征对本属植物分类及系统演化关系具有重要意义。     

春黄菊族6属植物种子的微形态特征

应用光学显微镜和扫描电镜对春黄菊族6属10种的种子微形态特征进行了比较观察。结果表明:10种种子在种子形态、表面纹饰、脐处的喙状突起、种子端的衣领状环等方面都表现出丰富的多样性,例如茼蒿的穴状和芫荽菊的细胞状纹饰等,具有明显的属级水平上的分类特征;在系和种级水平上,微形态特征虽有相似性,但仍具有一定的分类学价值,如龙蒿系圆头蒿的沟壑状纹饰和猪毛蒿系猪毛蒿的搓板状纹饰等。说明春黄菊族植物丰富的种子微形态特征在其系统分类中具有重要的参考价值;本研究结果支持栉叶蒿属、紊蒿属、茼蒿属独立成属的观点。     

谈地球生物学的重要意义

地球生物学是地球科学与生命科学交叉形成的一级学科,它研究作为地球系统三大基本过程之一的生命过程,即生物圈与地球其他圈层的相互作用.不仅是地球影响生物圈.而且生物圈也影响地球系统.这种相互作用或影响,从地球历史早期到现在,是一直在协同、耦合地进行着.生命与地球环境的协同演化是地球生物学的核心.当前地球生物学发展的重点是地球微生物学.宏体生物能反映地球环境对它们的影响及它们对环境的适应,但除植物外,它们对环境的影响有限.了解生物圈与地圈双向的相互作用必须研究地球微生物学.生命科学和整个自然科学都在向微观方向发展,不断形成新的理论和技术方法.古生物学不能停留在以古动、植物学为主的阶段,而要与生命科学和整个自然科学保持同步发展.现在我们已经找到了解决微生物与地质研究相结合问题的途径.微生物功能群具有重要的地质学意义,是研究地球微生物学的突破口.地球生物学是古生物学的继承和超越.分类系统学将仍然是研究的基础,但是包含了传统古生物学的地球生物学在学科内容和技术方法上将更多地与物理、化学、生物等学科交叉融合.其结果将使古生物学在时间上更前溯,在空间上更开拓,为古生物学在地球系统科学研究和为国民经济主战场服务中开辟更广阔的前景.     

野生经济植物与水土保持

目前我国人均占有的水、土资源少的情况下,既加强水土保持,恢复原有的生态系统,又为山区经济发展创造条件,以达到人与自然的和谐发展的工作中,野生经济植物资源的合理利用有着特别重要的作用。第一,许多好的经济植物是当地的乡土植物,适应当地的气候、土壤条件,稍加人工抚育即可成活、生长和取得较好的效益。第二,实行谁种植、谁管理、谁受益的制度,管理的投入可以从收入中提取,以减少国家对水土流失治理的投入。第三,发展优良的经济植物,也给全社会增加吃、穿、用的各种物质资源,有些可以出口创汇,增加国家财富积累。发展山区野生经济植物,对治理水土流失和增加农民收入都有重要的现实意义。     

How far and how fast can mushroom spores fly? Physical limits on ballistospore size and discharge distance in the Basidiomycota

Active discharge of basidiospores in most species of Basidiomycota is powered by the rapid movement of a droplet of fluid, called Buller’s drop, over the spore surface. This paper is concerned with the operation of the launch mechanism in species with the largest and smallest ballistospores. Aleurodiscus gigasporus (Russulales) produces the largest basidiospores on record. The maximum dimensions of the spores, 34 × 28 μm, correspond to a volume of 14 pL and to an estimated mass of 17 ng. The smallest recorded basidiospores are produced by Hyphodontia latitans (Hymenochaetales). Minimum spore dimensions in this species, 3.5 × 0.5 μm, correspond to a volume of 0.5 fL and mass of 0.6 pg. Neither species has been studied using high-speed video microscopy, but this technique was used to examine ballistospore discharge in species with spores of similar sizes (slightly smaller than A. gigasporus and slightly larger than those of H. latitans). Extrapolation of velocity measurements from these fungi provided estimates of discharge distances ranging from a maximum of almost 2 mm in A. gigasporus to a minimum of 4 μm in H. latitans. These are, respectively, the longest and shortest predicted discharge distances for ballistospores. Limitations to the distances traveled by basidiospores are discussed in relation to the mechanics of the discharge process and the types of fruit-bodies from which the spores are released.     

国产18种鳞盖蕨属植物叶表皮微形态特征及其系统学意义

鳞盖蕨属是一个自然类群,由于各类群之间的形态差异以及种内变异比较大,因此其分类一直存在争议。该研究利用光学显微镜(LM)和扫描电子显微镜(SEM)对鳞盖蕨属18种植物(含3变种)的叶表皮微形态进行了观察和比较,并结合形态学、孢粉学和分子系统学探讨其系统学意义。结果表明:在光学显微镜下,18种鳞盖蕨属植物叶上、下表皮的脉上均有毛,叶表皮细胞都为不规则形,垂周壁为深波状或波状; 气孔都分布在下表皮,气孔器类型主要有极细胞型和腋下细胞型两种,叶表皮微形态特征支持鳞盖蕨属是碗蕨科中的一个单系类群; 叶上、下表皮脉间毛的变异特征支持光叶鳞盖蕨、毛叶边缘鳞盖蕨和二回边缘鳞盖蕨处理为边缘鳞盖蕨变种; 在扫描电镜下,叶上表皮角质层多为脊状凸起,多数还具丝状纹饰,角质膜特征与叶片回数有一定的相关性; 共环极细胞型、聚腋下细胞型、不等细胞型和不规则四细胞型只在少数种出现,气孔外拱盖多数凹陷,光滑或有颗粒; 气孔外拱盖内缘平滑、浅波状或齿状; 保卫细胞两极大多数有“T”型加厚,不同种间叶表皮微形态特征表现出一定差异。该研究结果为其分类、演化、系统位置等进一步研究提供了参考。     

Metabolic characteristics of an aerobe isolated from a methylotrophic methanogenic enrichment culture

An anaerobic methylotrophic methanogenic enrichment culture, with sustained metabolic characteristics, including that of methanation for over a decade, was the choice of the present study on interspecies interactions. Growth and methanation by the enrichment were suppressed in the presence of antibiotics, and no methanogen grown on methanol could be isolated using stringent techniques. The present study confirmed syntrophic metabolic interactions in this enrichment with the isolation of a strain ofPseudomonas sp. The organism had characteristic metabolic versatility in metabolizing a variety of substrates including alcohols, aliphatic acids, amino acids, and sugars. Anaerobic growth was favoured with nitrate in the growth medium. Cells grown anaerobically with methanol, revealed maximal nitrate reductase activity. Constitutive oxidative activity of the membrane system emerged from the high-specific oxygen uptake and nitrate reductase activities of the aerobically and anerobically grown cells respectively. Cells grown anaerobically on various alcohols effectively oxidized methanol in the presence of flavins, cofactor FAD and the methanogenic cofactor F₄₂₀, suggesting a constitutive alcohol oxidizing capacity. In cells grown anaerobically on methanol, the rate of methanol oxidation with F₄₂₀ was three times that of FAD. Efficient utilization of alcohols in the presence of F₄₂₀ is a novel feature of the present study. The results suggest that utilization of methanol by the mixed culture would involve metabolic interactions between thePseudomonas sp. and the methanogen(s). Methylotrophic, methanogenic partnership involving an aerobe is a novel feature hitherto unreported among anaerobic syntrophic associations and is of ecological significance.