1. |
STRUCTURAL VALUE: A CONCEPT USED IN THE CONSTRUCTION OF TAXONOMIC CLASSIFICATIONS |
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TAXON,
Volume 28,
Issue 5-6,
2019,
Page 481-504
J. McNeill,
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摘要:
SummaryThe number of hierarchical clustering methods now available in numerical taxonomy is such as to be capable of yielding a bewilderingly large number of dendrograms. Moreover, mathematical criteria for choice of method have met with limited acceptance. The construction of dendrograms, whether on phenetic, eclectic, or cladistic principles, is not, however, the entire process of classification. Although both dendrograms and hierarchical classifications are ultrametric representations of relationship, the latter are always rank‐defined while the former may be defined on continuous distances. Even rank‐defined dendrograms are often so complex in terms of ranks and branching points (nodes) as to be unacceptable in practice as taxonomic classifications. In such cases a process of simplification is necessary beyond that involved in the ultrametric transformation. Although methods exist for assessing best ultrametric transformation, little consideration has been given to the subsequent simplification process. In this paper the criteria used by taxonomists in determining whether a classification shows an acceptable degree of simplification (e.g., by the compression or splitting of a dendrogram) are analysed. The extent to which a classification meets these criteria is termed itsstructural value.Psychological research has shown that the hierarchical organisation of stimuli aids memory and that the number of stimuli that can readily be considered at one time shows an upper limit of about five to seven. Hierarchical classification subdivides large groups into mentally more manageable ones (‘leaflets’ of a hierarchical tree) and it is suggested that the fewer additional taxa (nodes) and additional ranks required to do this, the higher the structural value. A structural value statistic (V) is developed which is the one‐complement of a loss function with terms representing the extent to which the leaflet sizes (nij) nodes (T) and ranks (r) are in excess. In the simplest case, whereais the desired leaflet size andT∗ andr∗ are the consequent ‘best’ number of nodes and ranks (not necessarily integral), the structural value of a classification ofNbasic taxa can be expressed asV=1‐∑i∑j(nij‐a)/(N+T)(T‐T*)/(N‐1)‐(r‐r*)/1nN,calculated only overni j>a, r>r∗,T>T∗. The structural value statistic is applied to a number of hypothetical situations and to a range of published classifications dating from 1753 to 1976. It is suggested that the statistic, which is essentially independent of the data used in assessing similarity, supplements the existing data‐dependent criteria for determining the quality of a classification and serves to specify more precisely one aspect of the hierarchical classificatory process.
ISSN:0040-0262
DOI:10.2307/1219786
出版商:Wiley
年代:2019
数据来源: WILEY
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2. |
AN ASSESSMENT OF CHEMICAL FEATURES FOR THE CLASSIFICATION OF PLANT FOSSILS |
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TAXON,
Volume 28,
Issue 5-6,
2019,
Page 505-516
Karl J. Niklas,
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摘要:
SummaryA list of 52 chemical characters is presented for preparing a numerical taxonomy of plant fossils. These characters may be used to determine (1) the degree of chemical similarity among various fossil taxa, (2) the maximum number and the state of characters needed to construct a suprageneric classification corresponding to one based on morphological features, (3) the nature of diagenesis effecting a divergence between chemical and morphological classifications, and (4) the utility of chemical characters in deriving phylogenetic relationships. Results from the analyses of 36 fossil taxa demonstrate the practicality of the proposed system, while comparisons of dendrograms obtained from chemical data and from classical criteria show good agreement. The approach taken in this study can provide an on‐line computer basis for the identification of plant fossils, provided that the environment of post‐depositional sediment maturation was sufficiently mild.
ISSN:0040-0262
DOI:10.2307/1219787
出版商:Wiley
年代:2019
数据来源: WILEY
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3. |
NUMERICAL ANALYSIS OF VARIATION BETWEENALLIUM CERNUUMANDALLIUM STELLATUM(LILIACEAE) |
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TAXON,
Volume 28,
Issue 5-6,
2019,
Page 517-523
T. D. Jacobsen,
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摘要:
SummaryVariability within and between two species of closely related onions (Allium cernuumRoth andAllium stellatumWats.) was measured using methods of cluster and principal component analysis. These two widely distributed but overlapping species are sometimes difficult to distinguish. Analysis with 62 characters supports the classification of the two as distinct taxa. The level of dissimilarity between the two taxa falls within the range of interspecies dissimilarity for the genus.
ISSN:0040-0262
DOI:10.2307/1219788
出版商:Wiley
年代:2019
数据来源: WILEY
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4. |
MEETINGS |
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TAXON,
Volume 28,
Issue 5-6,
2019,
Page 524-524
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ISSN:0040-0262
DOI:10.1002/j.1996-8175.1979.tb00548.x
出版商:Wiley
年代:2019
数据来源: WILEY
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5. |
IRIDOIDS INVERBENA |
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TAXON,
Volume 28,
Issue 5-6,
2019,
Page 525-528
S⊘ren Damtoft,
S⊘ren Rosendal Jensen,
Bent Juhl Nielsen,
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摘要:
SummarySeveral species ofVerbenawere examined for iridoid glucosides. These were found in all species of subgenusVerbenacainvestigated. In two of three species of the groupPachystachyaethe iridoid glucoside griselinoside was detected, while all species from the groupLeptostachyaecontained mixtures of cornin and the closely related hastatoside. The species from subgenusGlandulariaonly occasionally contained iridoids, and in no case were the compounds from subgenusVerbenacadetected.
ISSN:0040-0262
DOI:10.2307/1219790
出版商:Wiley
年代:2019
数据来源: WILEY
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6. |
NICKEL UPTAKE BY NEW CALEDONIAN SPECIES OFPHYLLANTHUS |
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TAXON,
Volume 28,
Issue 5-6,
2019,
Page 529-534
William J. Kersten,
Robert R. Brooks,
Roger D. Reeves,
Tanguy Jaffré,
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摘要:
SummaryHerbarium specimens (nearly 350) of New Caledonian species ofPhyllanthus(Euphorbiaceae) were analysed for their nickel and cobalt contents with a view to discovering new hyperaccumulators of nickel (>1000 μg/g dry mass) and to assisting in chemotaxonomic classification of this difficult genus. A total of 10 hyperaccumulators were identified and it was possible to characterise and identify a number of species from their nickel and/or cobalt contents. This was particularly true for the taxonomically difficult sectionHeteroglochidion.This work raises to 40 the number of known hyperaccumulators of nickel found in New Caledonia.
ISSN:0040-0262
DOI:10.2307/1219791
出版商:Wiley
年代:2019
数据来源: WILEY
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7. |
HISTORY OF THE CLASSIFICATION OF THE GENUSCAREX |
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TAXON,
Volume 28,
Issue 5-6,
2019,
Page 535-548
Alexander Robertson,
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摘要:
SummaryThe history of the classification of the genusCarexfrom 370 B.C.‐1955 A.D., including a synopsis of the etymology of the generic nameCarex, is reviewed. The refinement of descriptive terminology during the Middle Ages, caricology during the Renaissance period and the concepts of classification systems forCarexare also discussed.
ISSN:0040-0262
DOI:10.2307/1219792
出版商:Wiley
年代:2019
数据来源: WILEY
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8. |
INDIAN PODOPHYLLUM: IS ITPODOPHYLLUM EMODIORPODOPHYLLUM HEXANDRUM? |
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TAXON,
Volume 28,
Issue 5-6,
2019,
Page 549-551
Djaja D. Soejarto,
Robert B. Faden,
Norman R. Farnsworth,
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摘要:
SummaryThe source of Indian Podophyllum is variously referred to asPodophyllum emodiWall. orP. hexandrumRoyle. The latter is shown to be the earliest available name for this taxon.
ISSN:0040-0262
DOI:10.2307/1219793
出版商:Wiley
年代:2019
数据来源: WILEY
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9. |
NEWS OF HERBARIA AND COLLECTIONS |
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TAXON,
Volume 28,
Issue 5-6,
2019,
Page 552-552
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ISSN:0040-0262
DOI:10.1002/j.1996-8175.1979.tb00553.x
出版商:Wiley
年代:2019
数据来源: WILEY
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10. |
THE IDENTITY OFCORNUS CITRIFOLIAWESTON |
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TAXON,
Volume 28,
Issue 5-6,
2019,
Page 553-556
William J. Hess,
William T. Steam,
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摘要:
SummaryThe nameRhamnus citrifolia(Weston) Hess&Steam, based onCornus citrifoliaWeston (1770), replacesRhamnus davuricaPallas (1776) for a species widespread in northeastern Asia.
ISSN:0040-0262
DOI:10.2307/1219794
出版商:Wiley
年代:2019
数据来源: WILEY
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