模糊C－均值聚类和TWINSPAN分类的比较研究

以英国威尔士北部Ｓｎｏｗｄｏｎｉａ山地Ａｂｅｒ山谷植被为例,对模糊ｃ－均值聚类和ＴＷＩＮＳＰＡＮ分类进行了应用和比较研究。两种方法的结果一致。模糊ｃ－均值聚类结构给出样地和植被类型间的隶属程度,在一定程度上优于ＴＷＩＮＳＰＡＮ。     

三峡大老岭地区森林群落的数量分类研究

在大量的嫩落样方调查基础上,利用二元批示种分类法（ＴＷＩＮＳＰＡＮ）对三峡大老岭地区的森林群落进行数量分类,并据此划人会区山地植被垂直带的高度范围,讨论了ＴＷＩＮＳＰＡＮ方法的特点及其应用于结构复杂的亚热带木时应依据的原则。最后,文章总结了大老岭地区的森林群落类型。     

试用多元分析方法研究植物形态结构与生态环境的关系

应用多元分析方法对栎属高山栎组不同环境条件下的３３个植物样品的形态解剖性状的１７个指标进行了综合分析．结果表明,二元指示种分析（ＴＷＩＮＳＰＡＮ）聚类的结果能很好地把相似生态环境条件下的样品聚在一起,对样品进行无趋势对应分析（ＤＣＡ）和主成分分析（ＰＣＡ）都得到了满意结果．植物形态解剖性状的聚类、排序分析也可用来研究个体性状之间变异的连续性和间断性,进而有助于分类学的研究．     

有序样方聚类在植被垂直带划分中的应用

本文介绍一种非等级分类方法——有序样方聚类法,并将其应用于山西绵山植被垂直带的划分,结果为：１．落叶阔叶林带（包含３个亚带：Ⅰ．落叶阔叶灌丛亚带,Ⅱ．松栎林亚带,Ⅲ．落叶阔叶林亚带）,２．寒温性针叶林带和３．亚高山草甸带。基于黄金分割法（或Ｆｉｓｈｅｒ＇ｓ法）的有序样方聚类法,是按照样方在空间（或时间）先后出现的序号和组内相似性最大,组间相似性最小的标准,对样方进行分类,因此,所得结果是最优的。与ＴＷＩＮＳＰＡＮ的结果比较,在绵山植被遭到严重扰动的情况下,有序样方聚类要优于ＴＷＩＮＳＰＡＮ。     

中国东北西部地区沙质荒漠化过程与植被动态关系的生态学研究：植被的分类

根据东北沙质荒漠化地区呼化贝尔沙地、科尔沁沙地的７２个沙地植物群落样地、２７６种植物的调查数据,进行双向指标种分析（ＴＷＩＮＳＰＡＮ）,结合ＤＣＡ排序得到符合客观实际的分类结果,初步建立了中国东北沙质荒漠化地区植被分类系统,６个植被型,１１个植被亚型,４０个群系,５５个群丛。     

侧脑室注射一叶萩碱的心血管效应及作用机制

在麻醉大鼠侧脑室注射左旋一叶Ｑｉｕ碱（Ｌ－Ｓｅｃ）,记录动脉血压（ＡＰ）、心率（ＨＲ）及肾交感神经放电（ＲＳＮＤ）,观察前脑室周系统ＧＡＢＡ能紧张性活动改变引起的心血管效应。结果如下：（１）Ｌ－Ｓｅｃ可引起ＲＳＮＤ增加、ＡＰ升高和ＨＲ加快,并呈一定剂量－效应关系;但Ｌ－Ｓ盈余 于ｂｉｃｕｃｕｌｌｉｎｅ（Ｂｉｃ）。（２）Ｌ－Ｓｅｃ既能拮抗ｍｕｓｃｉｍｏｌ（Ｍｕｓ）,又能拮抗ｂａｃｌｏｆｅｎ（Ｂａｃ）     

吕梁山严村低中山区植物群落演替分析

采用一次性同时调查的方法获得数据,用数量分类（ＴＷＩＮＳＰＡＮ）和排序（ＤＣＡ）研究严村低中山植物群落演替。在黄土弃耕地上群落的演替顺序为：苦苣＋狗尾草群落（Ｃｏｍｍ．Ｉｘｅｒｉｓ ｃｈｉｎｅｎｓｉｓ ｓｓｐ．ｖｅｒｓｉｃｏｌｏｒ＋Ｓｅｔａｒｉａ ｖｉｒｉｄｉｓ）→蒿类群落（Ｃｏｍｍ．Ａｒｔｅｍｉｓｉａ ｓｐｐ．）→野艾蒿＋披碱草群落（Ｃｏｍｍ．Ａｒｔｅｍｉｓｉａ ｌａｖａｎｄｕｌａｅｆｏｌｉａ＋     

PARP酶抑制剂未引起整合的外源LacZ基因的丢失

使用聚ＡＤＰ核糖聚合酶（ＰＡＲＰ）ＮＡＤ位点抑制剂苯甲酰胺（ＢＡ）研究了降低ＰＡＲＰ酶活性对外源ＬａｃＺ基因整合稳定性的影响,利用ＤＮＡ体外重组技术将ＬａｃＺ基因全序列插入到真核表达载体载体ＰＳＶ２ｎｅｏ的ＨｉｎｄⅢ位点,构建了一个具有真核细胞ｎｅｏ基因筛选标记和ＬａｃＺ基因的真核表达重组体ＰＳＶ２ｎｅｏ－ｂｅｔａ－ｇａｌ将该重组体导入ＨｅＬａ细胞,经Ｇ４１８筛选获得了能稳定表达β－半乳糖苷酶的Ｈ     

抗真菌蛋白Rs—AFPs基因在大肠杆菌中的表达

将抗真菌蛋白Ｒｓ－ＡＦＰ１和Ｒｓ－ＡＦＰ２全长ｃＤＮＡ插入表达质粒ｐＥＴ－２２ｂ／ＮｃｏＩ＋ＳａｃＩ位点,构建成融合蛋白表达载体ｐＲＡＦ１和ｐＲＡＦ２．将不含信号肽编码序列的Ｒｓ－ＡＦＰ１和Ｒｓ－ＡＦＰ２ｃＤＮＡ分别插入ｐＥＴ－２２ｂ／Ｎｃｏｌ＋Ｓａｃｌ和ｐＥＴ－２２ｂ／Ｎｄｅｌ＋ＳａｃＩ位点,构建成不含信号肽序列的融合蛋白表达载体ｐＲＡＦ３、ｐＲＡＦ４和非融合蛋白表达载体ｐＲＡＦ５和ｐＲＡＦ６．将构建的上述各种表达载体转化Ｅ．ｃｏｌｉＢＬ２１,挑菌落培养,ＩＰＴＧ诱导,使Ｒｓ－ＡＦＰｓ基因得到表达,并用体外抑菌试验检测表达产物的活性,结果表明,各种表达载体的表达产物均具有不同程度的抑菌活性,其中,ｐＲＡＦ３和ｐＲＡＦ４表达产物的抑菌活性较明显．     

栝楼种子中一种新型小分子核糖体失活蛋白——S—tric …

通过硫酸铵分级沉淀、ＣＭ－５２阳离子交换层析、Ｓｅｐｈａｃｒｙｌ Ｓ－１００凝胶过滤和ＦＰＬＣ Ｍｏｎｏ－Ｓ离子交换层析等步骤,从栝楼种子中分离到一种核糖体失活蛋白－－Ｓ－ｔｒｉｃｈｏｋｉｒｉｎ,经１５％ＳＤＳ－ＰＡＧＥ测定分子量为８ｋＤ左右,１３．５％聚丙烯酰胺凝胶酸性电泳结果显示其等电点在ｐＨ９．５左右。通过对大鼠肝核糖体作用的研究,表明Ｓ－ｔｒｉ－ｃｈｏｋｉｒｉｎ属于ＲＮＡ Ｎ－糖苷酶催化型     

逐步聚类法及其应用

本文介绍了一种非等级分类方法——逐步聚类法,并将其应用于翅果油树灌丛的数量分类研究,结果表明：逐步聚类法实现最优分类的目标过程,是依样方组内具有最小的离差平方和。样方组间具有最大的离差平方和为标准,使样方组内具有最大的同质性,样方组间具有最大的异质性,其分类结果与实际情况吻合度较高;其次,逐步聚类法只需计算每个样方到该样方形心的距离,可缩短计算时间和节省计算机内存单元,提高工作效率。 与模糊c—均值聚类和TWINSPAN结果相比,逐步聚类的结果类似于模糊c—均值聚类,即样方组内具有较高的同质性;在不要求分类结果具有明显上下级关系的前提下,逐步聚类结果要优于TWINSPAN。     

A comparison of clustering methods for river benthic community analysis

Four commonly used clustering methods (UPGMA, Ward Linkage,Complete Linkage and TWINSPAN) were compared in their abilitytorecognise the structure of three river macroinvertebratesdatasetswhich were pre-determined based on habitat and biologicalcharacteristics or chemical water quality of sampling sites.DCA,NMDS and ANOSIM were applied to the same datasets to providefurther information about data structure, and nonparametrictestswere also undertaken on major chemical variables to justifythepredeterminations. The modified Rand Index was used to measuretheagreement between a particular solution and the pre-determinedclassification. The results showed that Ward Linkage performedbestwhen its use was broadened and used with the CY DissimilarityMeasure, followed by TWINSPAN and Complete Linkage with UPGMAbeingleast successful. There was evidence to suggest that theeffectiveness of some clustering methods (e.g. UPGMA) may varyatdifferent clustering levels, and simulation techniques whichhavebeen used to assess clustering methods could leave somepropertiesof clustering methods unexamined.     

Modern diatom assemblages in Central Mexico: the role of water chemistry and other environmental factors as indicated by TWINSPAN and DECORANA

SUMMARY. 1. Modern diatom samples, for which physical and chemical environmental conditions were recorded, were collected from forty-seven sites across Central Mexico
2. The results of the diatom counts were analysed using the clustering program TWINSPAN and the ordination program DECORANA.
3. Results from 'Laguna Zacapu and associated sites' showed that where water chemistry varies little between sample sites the effects of habitat are emphasized. This data set highlighted the problems of looking for modern analogues where anthropogenic disturbance is great.
4. TWINSPAN results from the 'Other Sites' data set suggested possible changes in diatom assemblages with chemical composition. The DECORANA analyses, however, again seemed to emphasize habitat.
5. In the context of this study, bottom sediment samples appeared to provide the most useful picture of 'average' conditions and to be the best source of analogues for the interpretation of fossil assemblages.     

Comparing three classification strategies for use in ecology

Abstract. We compare three common types of clustering algorithms for use with community data. TWINSPAN is divisive hierarchical, flexible-UPGMA is agglomerative and hierarchical, and ALOC is non-hierarchical. A balanced design six-factor model was used to generate 480 data sets of known characteristics. Recovery of the embedded clusters suggests that both flexible UPGMA and ALOC are significantly better than TWINSPAN. No significant difference existed between flexible UPGMA and ALOC.     

On computing the fuzzifier in downward arrow FLVQ: a data driven approach

Clustering is an important research area that has practical applications in many fields. Fuzzy clustering has shown advantages over crisp and probabilistic clustering, especially when there are significant overlaps between clusters. Most analytic fuzzy clustering approaches are derived from Bezdek's fuzzy c-means algorithm. One major factor that influences the determination of appropriate clusters in these approaches is an exponent parameter, called the fuzzifier. To our knowledge, no theoretical reason leading to an optimal setting of this parameter is available. This paper presents the development of an heuristic scheme for determining the fuzzifier. This scheme creates close interactions between the fuzzifier and the data set to be clustered. Experimental results in clustering IRIS data and in code book design required for image compression reveal a good performance of our proposal.     

长白山高山冻原植物群落的数量分类和排序

本文用目前在国际上比较先进的双向指示种分析(TWINSPAN)多元等级分划分类方法和无趋势对应分析(DCA)排序方法对长自山高山冻原植物群落进行了研究。研究结果表明:DCA的第2轴与长白山高山冻原59个植物群落类型的土壤水分梯度紧密相关, TWINSPAN将长白山高山冻原59个植物群落分为12组。此外, 本文还对长白山高山冻原植物群落的TWINSPAN和DCA分类结果与经典分类方法对其分类的结果进行了比较。     

Comparison of pattern recognition techniques for the identification of lactic acid bacteria

AIMS: The goal of this study was to evaluate three pattern recognition methods for use in the identification of lactic acid bacteria. METHODS AND RESULTS: Lactic acid bacteria (21 unknown isolates and 30 well-characterized strains), including the Lactobacillus, Lactococcus, Streptococcus, Pediococcus and Oenococcus genera, were tested for 49 phenotypic responses (acid production on carbon sources). The results were scored in several ways. Three procedures, k-nearest neighbour analysis (KNN), k-means clustering and fuzzy c-means clustering (FCM), were applied to the data. CONCLUSION: k-Nearest neighbour analysis performed better with five-point-scaled than with binary data, indicating that intermediate values are helpful to classification. k-Means clustering performed slightly better than KNN and was best with fuzzified data. The best overall results were obtained with FCM. Genus level classification was best with FCM using an exponent of 1.25. SIGNIFICANCE AND IMPACT OF THE STUDY: The three pattern recognition methods offer some advantages over other approaches to organism classification.     

不同稀有种处理对双向指示种分析分类结果影响的比较

为探讨不同稀有种处理对TWINSPAN分类结果的影响,以北京小龙门林场华北落叶松林调查数据为例,采用2×2列联表比较了剔除频度＜5%、盖度＜5%的稀有种前后TWINSPAN分类结果的异同,同时结合引入的DBI重点对比了最佳分类等级的吻合性。结果表明：(1)在相同的分类终止原则下,剔除稀有种前后的最大分类结果分别分为12、11个群落类型;(2)基于结合系数r,剔除稀有种前后TWINSPAN在低分类等级的结果差异较大,随着分类等级的增加,二者的吻合度增大,表明稀有种对低分类等级的结果影响较为明显;(3)引入的DBI适用于确定TWINSPAN分类的最佳分类等级,尽管剔除稀有种前后的最佳分类等级不同,但分类结果的吻合度较高。因此,在TWINSPAN分类应用中,建议引入DBI指数辅助确定最佳分类等级,同时取低分类等级结果时必须做删除稀有种处理。     

Classification of dry grassland vegetation in Denmark

Abstract. A hierarchic classification of Danish semi‐natural grassland vegetation on well‐drained soils is presented. TWINSPAN was used for clustering of 614 samples of grassland vegetation showing floristic gradients and turnover in species composition in more dimensions. The optimal hierarchic level of clustering was determined by indicator species analysis. The classification was interpreted in terms of variables relating to abiotic environment and vegetation structure and to major ecoclines previously identified by gradient analysis. The 12 final clusters were compared to syntaxa of formal phytosociology and to communities in the British Vegetation Classification. Criteria for achieving floristically homogeneous clusters without sacrificing the ecological interpretability and validity of the clusters in time and along geographical gradients are discussed.     

Evaluating classification strategies

Abstract. This contribution is a comment on the paper by Belbin & McDonald (1993) on the comparison of three classification strategies for use in ecology. There are two problems in evaluating clustering methods: does the sample adequately reflect the population structure, and what is the nature of the clusters sought. First, one has to decide on the number of clusters to be obtained. Possibly the best approach of all is the Bayesian coding theory for inductive inference. This may depend on the objectives of the clustering, which can be manifold. Phytosociologists do not agree on the nature of the clusters they seek, and are reticent in providing a formal definition of their clusters. As a method for identifying gradients Correspondence Analysis has had some success, so that a classification method largely based on it, notably TWINSPAN, may better reflect what phytosociologists are intuitively seeking than alternative variance minimisation methods. Additionally, TWINSPAN incorporates the characterisation through indicator species. Maybe we are more interested in these differentiating species than in the existence of clusters per se.