Journal articles: 'Structure dissimilarity'

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Zhang, Peng, Menghui Li, Jinshan Wu, Zengru Di, and Ying Fan. "The analysis and dissimilarity comparison of community structure." Physica A: Statistical Mechanics and its Applications 367 (July 2006): 577–85. http://dx.doi.org/10.1016/j.physa.2005.11.018.

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Jain, Pooja, and Jonathan D. Hirst. "Exploring protein structural dissimilarity to facilitate structure classification." BMC Structural Biology 9, no. 1 (2009): 60. http://dx.doi.org/10.1186/1472-6807-9-60.

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Sisodia, Dilip Singh, Shrish Verma, and Om Prakash Vyas. "Augmented intuitive dissimilarity metric for clustering of Web user sessions." Journal of Information Science 43, no. 4 (May 1, 2016): 480–91. http://dx.doi.org/10.1177/0165551516648259.

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Clustering is a very useful technique to categorise Web users with common browsing activities, access patterns and navigational behaviour. Web user clustering is used to build Web visitor profiles that make the core of a personalised information recommender system. These systems are used to comprehend Web users surfing activities by offering tailored content to Web users with similar interests. The principle objective of Web user sessions clustering is to maximise the intra-group while minimising the inter-group similarity. Efficient clustering of Web users’ sessions not only depend on the clustering algorithm’s nature but also depend on how well user concerns are captured and accommodated by the dissimilarity measure that are used. Determining the right dissimilarity measure to capture the access behaviour of the Web user is very significant for substantial clustering. In this paper, an intuitive dissimilarity measure is presented to estimate a Web user’s concern from augmented Web user sessions. The proposed usage dissimilarity measure between two Web user sessions is based on the accessing page relevance, the syntactic structure of page URL and hierarchical structure of the website. This proposed intuitive dissimilarity measure was used with K-Medoids Clustering algorithm for experimentation and results were compared with other independent dissimilarity measures. The worth of the generated clusters were evaluated by two unsupervised cluster validity indexes. The experimental results show that intuitive augmented session dissimilarity measure is more realistic and superior as compared to the other independent dissimilarity measures regarding cluster validity indexes.

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De Cáceres, Miquel, Pierre Legendre, and Fangliang He. "Dissimilarity measurements and the size structure of ecological communities." Methods in Ecology and Evolution 4, no. 12 (November 18, 2013): 1167–77. http://dx.doi.org/10.1111/2041-210x.12116.

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Hernández, Kevin Alejandro, D. Cárdenas Peña, and Álvaro A. Orozco. "A space-structure based dissimilarity measure for categorical data." International Journal of Electrical and Computer Engineering (IJECE) 11, no. 1 (February 1, 2021): 620. http://dx.doi.org/10.11591/ijece.v11i1.pp620-627.

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The development of analysis methods for categorical data begun in 90's decade, and it has been booming in the last years. On the other hand, the performance of many of these methods depends on the used metric. Therefore, determining a dissimilarity measure for categorical data is one of the most attractive and recent challenges in data mining problems. However, several similarity/dissimilarity measures proposed in the literature have drawbacks due to high computational cost, or poor performance. For this reason, we propose a new distance metric for categorical data. We call it: Weighted pairing (W-P) based on feature space-structure, where the weights are understood like a degree of contribution of an attribute to the compact cluster structure. The performance of W-P metric was evaluated in the unsupervised learning framework in terms of cluster quality index. We test the W-P in six real categorical datasets downloaded from the public UCI repository, and we make a comparison with the distance metric (DM3) method and hamming metric (H-SBI). Results show that our proposal outperforms DM3 and H-SBI in different experimental configurations. Also, the W-P achieves highest rand index values and a better clustering discriminant than the other methods.

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Gillet, V. J. "Similarity and Dissimilarity Methods for Processing Chemical Structure Databases." Computer Journal 41, no. 8 (August 1, 1998): 547–58. http://dx.doi.org/10.1093/comjnl/41.8.547.

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Tanioka, Kensuke, and Hiroshi Yadohisa. "Unfolding Models for Asymmetric Dissimilarity Data With External Information Based on Path Structures." International Journal of Software Innovation 6, no. 3 (July 2018): 53–66. http://dx.doi.org/10.4018/ijsi.2018070104.

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This article contains asymmetric dissimilarity data which is observed in various situations. In asymmetric dissimilarity data, dissimilarity from subject i to j and from subject j to i are not the same necessarily. Asymmetric multidimensional scaling (AMDS) is a visualization method for describing the asymmetric relations between subjects, given asymmetric dissimilarity data for subjects. It is sure that AMDS is a useful tool for interpreting the asymmetric relation, however, existing AMDS cannot be considered for the external information, even if the external information of the same subjects for the asymmetric dissimilarity data is given. If the estimated coordinates can be interpreted from the loading matrix for the external information like principal component analysis (PCA), the AMDS become more useful. This is because we can interpret the relation between the estimated asymmetries and the factors of the external information on the low dimensions. In this article, we proposed new AMDS with external information. In addition to that, the proposed method can consider the path structure for variables like SEM.

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Dinovitzer, R., and J. Hagan. "Hierarchical Structure and Gender Dissimilarity in American Legal Labor Markets." Social Forces 92, no. 3 (October 31, 2013): 929–55. http://dx.doi.org/10.1093/sf/sot110.

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Hammer, Barbara, and Alexander Hasenfuss. "Topographic Mapping of Large Dissimilarity Data Sets." Neural Computation 22, no. 9 (September 2010): 2229–84. http://dx.doi.org/10.1162/neco_a_00012.

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Topographic maps such as the self-organizing map (SOM) or neural gas (NG) constitute powerful data mining techniques that allow simultaneously clustering data and inferring their topological structure, such that additional features, for example, browsing, become available. Both methods have been introduced for vectorial data sets; they require a classical feature encoding of information. Often data are available in the form of pairwise distances only, such as arise from a kernel matrix, a graph, or some general dissimilarity measure. In such cases, NG and SOM cannot be applied directly. In this article, we introduce relational topographic maps as an extension of relational clustering algorithms, which offer prototype-based representations of dissimilarity data, to incorporate neighborhood structure. These methods are equivalent to the standard (vectorial) techniques if a Euclidean embedding exists, while preventing the need to explicitly compute such an embedding. Extending these techniques for the general case of non-Euclidean dissimilarities makes possible an interpretation of relational clustering as clustering in pseudo-Euclidean space. We compare the methods to well-known clustering methods for proximity data based on deterministic annealing and discuss how far convergence can be guaranteed in the general case. Relational clustering is quadratic in the number of data points, which makes the algorithms infeasible for huge data sets. We propose an approximate patch version of relational clustering that runs in linear time. The effectiveness of the methods is demonstrated in a number of examples.

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Guan, Hui, Chengzhen Jia, and Hongji Yang. "Intelligent recognition of semantic relationships based on antonymy." Multiagent and Grid Systems 16, no. 3 (October 30, 2020): 263–90. http://dx.doi.org/10.3233/mgs-200332.

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Since computing semantic similarity tends to simulate the thinking process of humans, semantic dissimilarity must play a part in this process. In this paper, we present a new approach for semantic similarity measuring by taking consideration of dissimilarity into the process of computation. Specifically, the proposed measures explore the potential antonymy in the hierarchical structure of WordNet to represent the dissimilarity between concepts and then combine the dissimilarity with the results of existing methods to achieve semantic similarity results. The relation between parameters and the correlation value is discussed in detail. The proposed model is then applied to different text granularity levels to validate the correctness on similarity measurement. Experimental results show that the proposed approach not only achieves high correlation value against human ratings but also has effective improvement to existing path-distance based methods on the word similarity level, in the meanwhile effectively correct existing sentence similarity method in some cases in Microsoft Research Paraphrase Corpus and SemEval-2014 date set.

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Haugaasen, Torbjørn, and Carlos A. Peres. "Mammal assemblage structure in Amazonian flooded and unflooded forests." Journal of Tropical Ecology 21, no. 2 (February 16, 2005): 133–45. http://dx.doi.org/10.1017/s026646740400207x.

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Few studies have contrasted faunal communities between flooded and unflooded tropical forests, and such attempts have largely been restricted to a few taxonomic groups. We present the first comparison of the composition and structure of an entire assemblage of mid-sized to large-bodied mammals in adjacent unflooded (terra firme) and flooded (várzea) forests of central-western Amazonia. We extend this comparison to 13 other terra firme and várzea forest sites in order to examine the fundamental dichotomy between mammal communities in these Amazonian environments. We found a consistently impoverished fauna in várzea environments both in terms of primates and other non-volant mammals, although primate density and biomass was substantially higher in várzea than in terra firme. The average Bray–Curtis mammal community dissimilarity between terra firme and várzea forests was 74%, whereas mean dissimilarity within várzea and terra firme samples was 40% and 39%, respectively. The results seem to be largely a function of high habitat heterogeneity and floristic diversity in terra firme and the physical connectivity and proximity of várzeas to adjacent terra firme forests. We suggest that inundated forests should be set aside as a crucial complement to Amazonian reserves dominated by terra firme forests in future biodiversity conservation planning.

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FUKUDOME, Koji, Takahiro TSUKAHARA, and Yoshifumi OGAMI. "Dissimilarity Analysis of Large-Scale Intermittent Flow Structure in Plane Couette Flow." Proceedings of Conference of Kansai Branch 2018.93 (2018): 808. http://dx.doi.org/10.1299/jsmekansai.2018.93.808.

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Deng, Wei, and Yihui Luan. "Analysis of Similarity/Dissimilarity of DNA Sequences Based on Chaos Game Representation." Abstract and Applied Analysis 2013 (2013): 1–6. http://dx.doi.org/10.1155/2013/926519.

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The Chaos Game is an algorithm that can allow one to produce pictures of fractal structures. Considering that the four bases A, G, C, and T of DNA sequences can be divided into three classes according to their chemical structure, we propose different kinds of CGR-walk sequences. Based on CGR coordinates of random sequences, we introduce some invariants for the DNA primary sequences. As an application, we can make the examination of similarity/dissimilarity among the first exon ofβ-globin gene of different species. The results indicate that our method is efficient and can get more biological information.

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Wang, Juan, and Maozu Guo. "A review of metrics measuring dissimilarity for rooted phylogenetic networks." Briefings in Bioinformatics 20, no. 6 (July 17, 2018): 1972–80. http://dx.doi.org/10.1093/bib/bby062.

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Abstract A rooted phylogenetic network is an important structure in the description of evolutionary relationships. Computing the distance (topological dissimilarity) between two rooted phylogenetic networks is a fundamental in phylogenic analysis. During the past few decades, several polynomial-time computable metrics have been described. Here, we give a comprehensive review and analysis on those metrics, including the correlation among metrics and the distribution of distance values computed by each metric. Moreover, we describe the software and website, CDRPN (Computing Distance for Rooted Phylogenetic Networks), for measuring the topological dissimilarity between rooted phylogenetic networks. Availability http://bioinformatics.imu.edu.cn/distance/ Contact guomaozu@bucea.edu.cn

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Danner, Moeses Andrigo, Idemir Citadin, Simone Aparecida Zolet Sasso, Silvia Scariot, and Giovani Benin. "Genetic dissimilarity among jabuticaba trees native to southwestern Paraná, Brazil." Revista Brasileira de Fruticultura 33, no. 2 (July 15, 2011): 517–25. http://dx.doi.org/10.1590/s0100-29452011005000078.

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Knowledge on the genetic diversity within and between genotype groups is of great importance for breeding programs. The purpose of this study was to estimate the genetic dissimilarity among 36 native jabuticaba trees (Plinia cauliflora) from five sites in the southwestern region of Paraná, Brazil. Sixteen fruit traits were analyzed, based on multivariate techniques (canonical variables, Tocher and UPGMA), using Mahalanobis' distance as dissimilarity measure. By the techniques of clustering and graphic dispersion, together with the comparison of means, the genetic diversity among native jabuticaba trees was efficiently identified, indicating a high potential of these genotypes for breeding programs. The traits of greatest importance for dissimilarity were percentage of pulp and of skin, which are easily measured. The clustering structure is related to the collection sites and for breeding programs, genotypes from different sites should be crossed to generate progenies to be tested. Genotypes 'CV5' and 'VT3' should be conserved in genebanks, due to its important agronomic traits.

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Grishin, John, and Douglas J. Gillan. "Structure Matters: Effects of Semantic Relatedness and Proximity on Consumer Search and Integration Tasks." Proceedings of the Human Factors and Ergonomics Society Annual Meeting 60, no. 1 (September 2016): 1088–92. http://dx.doi.org/10.1177/1541931213601251.

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Information displays should be clear and easily understood. This research examined whether principles developed by Kosslyn (1989) and Carswell and Wickens (1987) for charts, graphs, and object displays could be extended, or adapted, to another type of display, the food item package. We hypothesized that a food package on which label items had been arranged according to their similarity, or semantic relatedness, would facilitate better user performance than a package on which label items had been arranged in other ways. Participants rated the semantic relatedness of 12 label items found on a common food item package. Using multi-dimensional scaling (MDS) outputs from the ratings, we created three versions of a consumer cough drop package: 1) Similarity version—label elements that received higher similarity ratings were depicted closer together than elements with lower similarity ratings, 2) Dissimilarity version—elements that received higher similarity ratings were depicted farther apart than elements with lower similarity ratings, 3) Random version—rating values were randomly assigned to the pairs of elements. We tested user performance on search tasks and integrative tasks on each of the three versions. We hypothesized that the Similarity version would produce the best user performance and the Dissimilarity version would produce the worst. Results only partially supported the hypotheses. On the search tasks, the best performance was achieved on the Similarity and Dissimilarity versions, and the worst on the Random version. On the integrative tasks, the version made no difference in performance. Possible reasons for these results are discussed. Similar results by Fitts and Deininger (1954) and Morin and Grant (1955) suggest that performance on tasks are superior when the relationships are in an ordered structure, rather than randomly assigned, possibly because ordered structures make possible the development of search strategies, whereas random arrangements do not.

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SUOMINEN, Lassi, Kalle RUOKOLAINEN, Timo PITKÄNEN, and Hanna TUOMISTO. "Similar understorey structure in spite of edaphic and floristic dissimilarity in Amazonian forests." Acta Amazonica 45, no. 4 (December 2015): 393–404. http://dx.doi.org/10.1590/1809-4392201500132.

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Forest structure determines light availability for understorey plants. The structure of lowland Amazonian forests is known to vary over long edaphic gradients, but whether more subtle edaphic variation also affects forest structure has not beenresolved. In western Amazonia, the majority of non-flooded forests grow on soils derived either from relatively fertile sediments of the Pebas Formation or from poorer sediments of the Nauta Formation. The objective of this study was to compare structure and light availability in the understorey of forests growing on these two geological formations. We measured canopy openness and tree stem densities in three size classes in northeastern Peru in a total of 275 study points in old-growth terra firme forests representing the two geological formations. We also documented variation in floristic composition (ferns, lycophytes and the palm Iriartea deltoidea) and used Landsat TM satellite image information to model the forest structural and floristic features over a larger area. The floristic compositions of forests on the two formations were clearly different, and this could also be modelled with the satellite imagery. In contrast, the field observations of forest structure gave only a weak indication that forests on the Nauta Formation might be denser than those on the Pebas Formation. The modelling of forest structural features with satellite imagery did not support this result. Our results indicate that the structure of forest understorey varies much less than floristic composition does over the studied edaphic difference.

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Schlueter-Kuck, Kristy L., and John O. Dabiri. "Coherent structure colouring: identification of coherent structures from sparse data using graph theory." Journal of Fluid Mechanics 811 (December 13, 2016): 468–86. http://dx.doi.org/10.1017/jfm.2016.755.

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We present a frame-invariant method for detecting coherent structures from Lagrangian flow trajectories that can be sparse in number, as is the case in many fluid mechanics applications of practical interest. The method, based on principles used in graph colouring and spectral graph drawing algorithms, examines a measure of the kinematic dissimilarity of all pairs of fluid trajectories, measured either experimentally, e.g. using particle tracking velocimetry, or numerically, by advecting fluid particles in the Eulerian velocity field. Coherence is assigned to groups of particles whose kinematics remain similar throughout the time interval for which trajectory data are available, regardless of their physical proximity to one another. Through the use of several analytical and experimental validation cases, this algorithm is shown to robustly detect coherent structures using significantly less flow data than are required by existing spectral graph theory methods.

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SONG, JIE. "ANALYSIS OF SIMILARITY/DISSIMILARITY OF DNA SEQUENCES BY A NEW 3D GRAPHICAL REPRESENTATION." Journal of Biological Systems 15, no. 03 (September 2007): 287–97. http://dx.doi.org/10.1142/s0218339007002234.

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A new 3D graphical representation of DNA sequences according to chemical structures of the bases is proposed, reflecting the distribution of bases with different chemical structure, preserving information on sequential adjacency of bases, avoiding loss of information accompanying alternative 3D representations in which the curve standing for DNA overlaps and intersects itself. Based on this representation, a numerical characterization approach is presented by constructing a six-component vector whose components are the normalized leading eigenvalues of the L/L matrices associated with the DNA sequences. The examination of similarities among the coding sequences of the first exon of β-globin gene of different species illustrates the utility of the approach.

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Husic, Brooke E., Kristy L. Schlueter-Kuck, and John O. Dabiri. "Simultaneous coherent structure coloring facilitates interpretable clustering of scientific data by amplifying dissimilarity." PLOS ONE 14, no. 3 (March 13, 2019): e0212442. http://dx.doi.org/10.1371/journal.pone.0212442.

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AISAKA, Shunpei, Kenji KATOH, and Tatsuro WAKIMOTO. "117 Influence of turbulent vortex structure on dissimilarity Between heat and momentum transfer." Proceedings of Conference of Kansai Branch 2012.87 (2012): _1–42_. http://dx.doi.org/10.1299/jsmekansai.2012.87._1-42_.

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Hara, Shumpei, Takahiro Tsukahara, and Yasuo Kawaguchi. "Turbulent transport dissimilarity with modulated turbulence structure in channel flow of viscoelastic fluid." International Journal of Heat and Fluid Flow 86 (December 2020): 108739. http://dx.doi.org/10.1016/j.ijheatfluidflow.2020.108739.

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Del Olmo-Ruiz, Mariana, and A. Elizabeth Arnold. "Community structure of fern-affiliated endophytes in three neotropical forests." Journal of Tropical Ecology 33, no. 1 (November 2, 2016): 60–73. http://dx.doi.org/10.1017/s0266467416000535.

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Abstract:From the saprotrophs that decay plant material to the pathogens and mutualists that shape plant demography at local and regional scales, fungi are major drivers of tropical forest dynamics. Although endophytic fungi are abundant and diverse in many biomes, they reach their greatest diversity in tropical forests, where they can influence plant physiology, performance and survival. The number of quantitative studies regarding endophytes has increased dramatically in the past two decades, but general rules have not yet emerged regarding the biogeography, host affiliations, local or regional distributions, or phylogenetic diversity of endophytes in most tropical settings. Here, endophytic fungal communities associated with 18 species of eupolypod fern were compared among forest reserves in Panama, Costa Rica and Mexico. Molecular sequence data for >2000 isolates were used to determine the relationships of host taxonomy, forest (site), and environmental dissimilarity to endophyte community composition. Communities in related ferns differed significantly among forests, reflecting the interplay of geographic distance and environmental dissimilarity. Although the same phyla and classes of fungi were prevalent at each site, they differed in relative abundance. All sites were dominated by the same order (Xylariales), but sites differed in the phylogenetic clustering vs. evenness of their endophyte communities. By addressing the relationship of endophyte communities to host taxonomy, geographic distance and environmental factors, this study complements previous work on angiosperms and contributes to a growing perspective on the factors shaping communities of ecologically important fungi in tropical forests.

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Sung, Ha-Cheol, and Paul Handford. "Songs of the Savannah Sparrow: structure and geographic variation." Canadian Journal of Zoology 84, no. 11 (November 2006): 1637–46. http://dx.doi.org/10.1139/z06-159.

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We investigated song structure and the pattern of geographic variation at the syllable and whole song levels in Savannah Sparrow, Passerculus sandwichensis (J.F. Gmelin, 1789). Songs were recorded for 179 males from eight sample populations distributed along a 230 km transect in southwestern Ontario in 2000. Subsequent analysis included measurement and comparison of structural song features and qualitative analysis of syllable and song type similarity among individuals both within and among populations, by reference to a syllable catalogue based on syllable similarity. Song type sharing within samples was not common, while song dissimilarity significantly correlated with distance among samples. Overall south–north trends appeared in two aspects of quantitative and qualitative characteristics, and the geographic differentiation of Savannah Sparrow songs was gradual, increasing with distance. At a higher level of analysis, two song groups, with qualitatively distinct structures (here termed themes), were identified. These themes showed a clinal intergrade, such that one theme was found in all individuals of the four southern samples, while in the four more northerly samples, the second theme's incidence grew progressively from 20% to 80%. However, birds singing the southern theme in populations dominated by the northern theme nevertheless produced songs that show metrical (frequency and duration) characteristics typical of the northern theme songs from their own population. Cluster analysis based on syllable and song type similarity–dissimilarity between populations linked geographically neighboring populations closely, while populations fell into two main clusters: the three most northerly and the five most southerly populations. The same cluster pattern also appeared within each theme type.

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Mariani, Simone, Susana Pinedo, Marc Terradas, Maria Elena Cefalì, Eglantine Chappuis, and Enric Ballesteros. "Habitat structure and zonation patterns of northwestern Mediterranean shoreline strands." Scientia Marina 81, no. 2 (June 14, 2017): 269. http://dx.doi.org/10.3989/scimar.04445.09a.

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We studied the habitat structure (macrofaunal assemblages and bottom types) and zonation patterns of 29 unvegetated shoreline strands along the 900-km coast of Catalonia (NW Mediterranean Sea). Organisms were sampled with grabs, pitfall traps, sticky traps, clam nets and spades to ensure capture of the different proportions of macrofaunal assemblages from the supra-, medio- and infralittoral levels. We collected 211 taxa: 194 animals and 17 algae. The most abundant and dominant organisms collected with van Veen grabs were Nematoda, Oligochaeta and Collembola at the supralittoral level; the polychaetes Saccocirrus spp. and Pisione remota, the amphipod Corophium orientale, Nematoda, and Turbellaria at the mediolittoral level; and Nematoda at the upper infralittoral level. SIMPER analysis revealed great dissimilarity between the organisms inhabiting the supralittoral and the other littoral levels. Regarding the epifauna, the sticky traps used at the supralittoral level mainly collected Collembola, which were nearly absent in pitfall traps. The qualitative study performed with a clam net and a small spade revealed that Nematoda, Saccocirrus spp., Turbellaria, Nemertea and the polychaete P. remota were the most abundant animals at both the medio- and the infralittoral levels and no differences were found between these levels. Different qualitative sampling methodologies showed that in fine sediments the bivalves Donax trunculus and D. semistriatus determined more than 97% of dissimilarity from coarse-sand sites. Richness increased in protected sandy and cobble shores. Littoral level and bottom-type features were only to a certain extent valid indicators of specific biotic components for a specific habitat.

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Mackay, David B., Robert F. Easley, and Joseph L. Zinnes. "A Single Ideal Point Model for Market Structure Analysis." Journal of Marketing Research 32, no. 4 (November 1995): 433–43. http://dx.doi.org/10.1177/002224379503200405.

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Computing unsegmented product maps from preference data by means of single ideal point models is commonly thought to be impossible because of indeterminacy problems. The authors show that this mathematical indeterminacy can be overcome by incorporating dependent sampling assumptions into a probabilistic multidimensional scaling (MDS) model. As a result, product space maps can be estimated for single markets from preference data alone. If desired, dissimilarity data can be combined with preference data to produce jointly estimated product space maps. The authors illustrate the advantages of the proposed approach with real and simulated data. They also make comparisons to both internal and external deterministic models. The results are favorable.

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Furumoto, T., T. Suhara, and N. Itagaki. "Study of similarity and dissimilarity between10Be and9Li nuclei with microscopic structure and reaction models." Journal of Physics: Conference Series 863 (June 2017): 012014. http://dx.doi.org/10.1088/1742-6596/863/1/012014.

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LEE, WAN-JUI, VERONIKA CHEPLYGINA, DAVID M. J. TAX, MARCO LOOG, and ROBERT P. W. DUIN. "BRIDGING STRUCTURE AND FEATURE REPRESENTATIONS IN GRAPH MATCHING." International Journal of Pattern Recognition and Artificial Intelligence 26, no. 05 (August 2012): 1260005. http://dx.doi.org/10.1142/s0218001412600051.

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Structures and features are opposite approaches in building representations for object recognition. Bridging the two is an essential problem in pattern recognition as the two opposite types of information are fundamentally different. As dissimilarities can be computed for both the dissimilarity representation can be used to combine the two. Attributed graphs contain structural as well as feature-based information. Neglecting the attributes yields a pure structural description. Isolating the features and neglecting the structure represents objects by a bag of features. In this paper we will show that weighted combinations of dissimilarities may perform better than these two extremes, indicating that these two types of information are essentially different and strengthen each other. In addition we present two more advanced integrations than weighted combining and show that these may improve the classification performances even further.

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Spach, Henry L., Rodrigo S. Godefroid, César Santos, Roberto Schwarz Jr., and Guilherme M. L. de Queiroz. "Temporal variation in fish assemblage composition on a tidal flat." Brazilian Journal of Oceanography 52, no. 1 (March 2004): 47–58. http://dx.doi.org/10.1590/s1679-87592004000100005.

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Annual variation in the fish assemblage characteristics on a tidal flat was studied in coastal Paraná, in southern Brazil. Fish were collected between August 1998 and July 1999, during the diurnal high tide and diurnal and nocturnal low tide of the syzygial (full moon) and quadrature (waning moon) tides, to characterize temporal change in assemblage composition. A total of 64,265 fish in 133 species were collected. The average number of species and individuals, biomass, species richness, diversity (mass) and equitability varied significantly over time . The dissimilarity of the assemblage was greatest in August, September and October in contrast with the period from November to January, with the lowest dissimilarity. The combined action of water temperature, salinity and wind intensity had a great influence over the structure of the fish assemblage.

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Kandlikar, Gaurav S., Marcel C. Vaz, Ricardo Kriebel, German Vargas, Fabián A. Michelangeli, Roberto Cordero, Frank Almeda, Gerardo Avalos, Ned Fetcher, and Nathan J. B. Kraft. "Contrasting patterns of taxonomic, phylogenetic and functional variation along a Costa Rican altitudinal gradient in the plant family Melastomataceae." Journal of Tropical Ecology 34, no. 3 (May 2018): 204–8. http://dx.doi.org/10.1017/s0266467418000172.

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Abstract:The functional composition of plant communities in montane regions has been studied for decades, and most recent analyses find that environmentally favourable landscapes at lower altitudes tend to be dominated by species with resource-acquisitive traits, while more resource-conservative taxa dominate higher-altitude communities. However, it is unclear the extent to which this pattern is driven by co-gradient variation within clades or changes in clade representation across the gradient. To test for co-gradient variation, species composition, phylogenetic structure and functional traits were quantified for 97 species within the plant family Melastomataceae at five locations across a 2500-m altitudinal gradient along Volcán Barva in Costa Rica. Average melastome leaf force to punch, specific leaf area and leaf size vary with altitude, while four other functional traits do not. Taxonomic dissimilarity between communities was correlated with altitudinal difference, while phylogenetic dissimilarity was correlated with altitudinal dissimilarity only when measured with a metric that emphasizes shallow turnover of the tips of the phylogeny. These results highlight how species turnover may be more pronounced than functional or phylogenetic variation along altitudinal gradients. In addition, these results highlight the conservation value of lowland tropical forests, which here harbour a disproportionate amount of phylogenetic and functional diversity.

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Beule, Lukas, and Petr Karlovsky. "Improved normalization of species count data in ecology by scaling with ranked subsampling (SRS): application to microbial communities." PeerJ 8 (August 3, 2020): e9593. http://dx.doi.org/10.7717/peerj.9593.

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Background Analysis of species count data in ecology often requires normalization to an identical sample size. Rarefying (random subsampling without replacement), which is the current standard method for normalization, has been widely criticized for its poor reproducibility and potential distortion of the community structure. In the context of microbiome count data, researchers explicitly advised against the use of rarefying. Here we introduce a normalization method for species count data called scaling with ranked subsampling (SRS) and demonstrate its suitability for the analysis of microbial communities. Methods SRS consists of two steps. In the scaling step, the counts for all species or operational taxonomic units (OTUs) are divided by a scaling factor chosen in such a way that the sum of scaled counts equals the selected total number of counts Cmin. The relative frequencies of all OTUs remain unchanged. In the subsequent ranked subsampling step, non-integer count values are converted into integers by an algorithm that minimizes subsampling error with regard to the population structure (relative frequencies of species or OTUs) while keeping the total number of counts equal Cmin. SRS and rarefying were compared by normalizing a test library representing a soil bacterial community. Common parameters of biodiversity and population structure (Shannon index H’, species richness, species composition, and relative abundances of OTUs) were determined for libraries normalized to different size by rarefying as well as SRS with 10,000 replications each. An implementation of SRS in R is available for download (https://doi.org/10.20387/BONARES-2657-1NP3). Results SRS showed greater reproducibility and preserved OTU frequencies and alpha diversity better than rarefying. The variance in Shannon diversity increased with the reduction of the library size after rarefying but remained zero for SRS. Relative abundances of OTUs strongly varied among libraries generated by rarefying, whereas libraries normalized by SRS showed only negligible variation. Bray–Curtis index of dissimilarity among replicates of the same library normalized by rarefying revealed a large variation in species composition, which reached complete dissimilarity (not a single OTU shared) among some libraries rarefied to a small size. The dissimilarity among replicated libraries normalized by SRS remained negligibly low at each library size. The variance in dissimilarity increased with the decreasing library size after rarefying, whereas it remained either zero or negligibly low after SRS. Conclusions Normalization of OTU or species counts by scaling with ranked subsampling preserves the original community structure by minimizing subsampling errors. We therefore propose SRS for the normalization of biological count data.

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Koszela, Grzegorz. "Use gradation data analysis to the classification of sub-regions in terms of the agrarian structure." Wiadomości Statystyczne. The Polish Statistician 61, no. 6 (June 28, 2016): 10–30. http://dx.doi.org/10.5604/01.3001.0014.1001.

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The article deals with the problem of measuring the dissimilarity structures. It turned out that the proposed measure, built by analogy with the Gini coefficient, can capture the subtleties, to which are not sensitive measure based on the metrics, commonly used in the literature. This paper presents a way to visualize structures using maps over-representation and ways of grouping objects by gradation data analysis. The groupings results are shown in comparison with the results obtained by other methods.

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Lemos, Helena Lara, José Roberto Rodrigues Pinto, Henrique Augusto Mews, and Eddie Lenza. "Structure and floristic relationships between Cerrado sensu stricto sites on two types of substrate in northern Cerrado, Brazil." Biota Neotropica 13, no. 4 (December 2013): 121–32. http://dx.doi.org/10.1590/s1676-06032013000400013.

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We described and compared the floristic composition, richness, species diversity and structure of the tree-shrub component in pairs of Typical Cerrado (Cerrado Típico) and rocky outcrop Cerrado (Cerrado Rupestre) in two localities in Tocantins State. In each locality, we set up 10 plots of 20 × 50 m at a site, the Cerrado Típico and other Cerrado Rupestre, and sampled the individuals with Db30cm ≥ 5 cm. The rocky outcrop Cerrado did not present any trend towards lower richness and basal area compared to the Cerrado on deep soil. Few species occurred across the four sites and only two important species (Anacardium occidentale and Qualea parviflora) in the four vegetation structure were common to both environments assessed. Furthermore, the occurrence of habitat-specialist species of rocky outcrops and high altitudes (Mimosa claussenii, Tibouchina papyrus, Schwartzia adamantium and Wunderlichia cruelsiana) and the high dissimilarity among sites suggest that altitude is the main responsible for the floristic dissimilarity, followed by the influence of substrate type. Therefore, the information with respect to phytophysiognomy type as a parameter to select areas for conservation, by itself, does not effectively ensure biodiversity preservation, owing to the existing flora heterogeneity not only at local but also at regional scale, revealed by the floristic and structural particularity of each site.

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Ficetola, Gentile Francesco, Mattia Falaschi, Anna Bonardi, Emilio Padoa-Schioppa, and Roberto Sindaco. "Biogeographical structure and endemism pattern in reptiles of the Western Palearctic." Progress in Physical Geography: Earth and Environment 42, no. 2 (April 2018): 220–36. http://dx.doi.org/10.1177/0309133318765084.

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The analysis of biogeographical structure and patterns of endemism are central topics of biogeography, but require exhaustive distribution data. A lack of accurate broad-scale information on the distribution of reptiles has so far limited the analyses of biogeographical structure. Here we analysed the distribution of reptiles within the broad-sense Western Palearctic to assess biogeographical regionalization using phylogenetic and non-phylogenetic approaches, identified areas of endemism and evaluated the environmental factors promoting community uniqueness and endemism. We gathered distributional records from the literature and from the field, mapping the distribution of all the Western Palearctic reptiles on a 1-degree resolution grid. βsim dissimilarity and hierarchical clustering was used to identify bioregions, analysing data both at the species and at the genus level, and considering phylogenetic dissimilarity. Consensus areas of endemism were identified on the basis of the optimality criterion. We then assessed whether biogeographical structure is related to present-day climate, insularity, orography and velocity of climate change during the Late Quaternary. The genus-level analysis identified five main biogeographical regions within the Western Palearctic, in partial agreement with previous proposals, while the species-level analysis identified more bioregions, largely by dividing the ones identified by genera. Phylogenetic bioregions were generally consistent with the non-phylogenetic ones. The strongest community uniqueness was observed in subtropical warm climates with seasonal precipitation and low productivity. We found nine consensus areas of endemism, mostly in regions with limited velocity of Quaternary climate change and warm subtropical climates. The biogeographical structure of Western Palearctic reptiles is comparable to what has been observed in other vertebrates, with a clear distinction between the Saharo-Arabian-Sindian and Euro-Mediterranean herpetofaunas. Unlike other vertebrates, in reptiles the highest uniqueness and endemism is observed in dry climates, but the velocity of climate change during the Quaternary remains a major driver of endemism across all the vertebrates.

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Brill, Michael, and Frank Schwab. "T-pattern analysis and spike train dissimilarity for the analysis of structure in blinking behavior." Physiology & Behavior 227 (December 2020): 113163. http://dx.doi.org/10.1016/j.physbeh.2020.113163.

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Katayama-Yoshida, H., and T. Takahashi. "Similarity and dissimilarity of doped fullerenes and oxide superconductors from the viewpoint of electronic structure." Journal of Physics and Chemistry of Solids 54, no. 12 (December 1993): 1817–24. http://dx.doi.org/10.1016/0022-3697(93)90294-2.

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Bogdanowicz, Damian, and Krzysztof Giaro. "On a matching distance between rooted phylogenetic trees." International Journal of Applied Mathematics and Computer Science 23, no. 3 (September 1, 2013): 669–84. http://dx.doi.org/10.2478/amcs-2013-0050.

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Abstract The Robinson-Foulds (RF) distance is the most popular method of evaluating the dissimilarity between phylogenetic trees. In this paper, we define and explore in detail properties of the Matching Cluster (MC) distance, which can be regarded as a refinement of the RF metric for rooted trees. Similarly to RF, MC operates on clusters of compared trees, but the distance evaluation is more complex. Using the graph theoretic approach based on a minimum-weight perfect matching in bipartite graphs, the values of similarity between clusters are transformed to the final MC-score of the dissimilarity of trees. The analyzed properties give insight into the structure of the metric space generated by MC, its relations with the Matching Split (MS) distance of unrooted trees and asymptotic behavior of the expected distance between binary n-leaf trees selected uniformly in both MC and MS (Θ(n3/2)).

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Ikuesan, Adeyemi R., Mazleena Salleh, Hein S. Venter, Shukor Abd Razak, and Steven M. Furnell. "A heuristics for HTTP traffic identification in measuring user dissimilarity." Human-Intelligent Systems Integration 2, no. 1-4 (June 2, 2020): 17–28. http://dx.doi.org/10.1007/s42454-020-00010-2.

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AbstractThe prevalence of HTTP web traffic on the Internet has long transcended the layer 7 classification, to layers such as layer 5 of the OSI model stack. This coupled with the integration-diversity of other layers and application layer protocols has made identification of user-initiated HTTP web traffic complex, thus increasing user anonymity on the Internet. This study reveals that, with the current complex nature of Internet and HTTP traffic, browser complexity, dynamic web programming structure, the surge in network delay, and unstable user behavior in network interaction, user-initiated requests can be accurately determined. The study utilizes HTTP request method of GET filtering, to develop a heuristic algorithm to identify user-initiated requests. The algorithm was experimentally tested on a group of users, to ascertain the certainty of identifying user-initiated requests. The result demonstrates that user-initiated HTTP requests can be reliably identified with a recall rate at 0.94 and F-measure at 0.969. Additionally, this study extends the paradigm of user identification based on the intrinsic characteristics of users, exhibited in network traffic. The application of these research findings finds relevance in user identification for insider investigation, e-commerce, and e-learning system as well as in network planning and management. Further, the findings from the study are relevant in web usage mining, where user-initiated action comprises the fundamental unit of measurement.

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Markowska, Małgorzata. "Decomposition of changes in structure and trends in employment in Czechia at NUTS 2 level." GeoScape 11, no. 2 (December 1, 2017): 84–92. http://dx.doi.org/10.1515/geosc-2017-0007.

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AbstractObserving the structure of employment and its trends constitute the fundamental baseline to assess the successes and failures of both national and EU social and economic policies in terms of evaluating effectiveness of support to regions framed by both competitiveness and cohesion issues. The study presents the assessment of structural changes of employment in the system of traditional three economic sectors using the measure of structures dissimilarity along with its decomposition and trends. The Czech NUTS 2 level regions were used for the study and the analysed period covered the years 2008−2014. TheUmeasure of changes in structure of components was applied on data on employment (NACE classification). The results confirmed the current trends of (i) tertiarization in old industrial regions; (ii) the increasing share of employment in the industrial sector shown by some rural regions, and (iii) the growing fragmentation of the spatial pattern of socio-economic development.

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Lebacher, Michael, Paul W. Thurner, and Göran Kauermann. "Exploring dependence structures in the international arms trade network: A network autocorrelation approach." Statistical Modelling 20, no. 2 (January 17, 2019): 195–218. http://dx.doi.org/10.1177/1471082x18817673.

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In this article, we analyse dependence structures among international trade flows of major conventional weapons from 1952 to 2016. We employ a Network Disturbance Model commonly used in inferential network analysis and spatial econometrics. The dependence structure is represented by pre-defined weight matrices that allow for correlating flows from the network of international arms exchange. Three dependence structures are proposed, representing sender-, receiver- and sender–receiver-related dependencies. The appropriateness of the presumed structures is comparatively assessed using the Akaike Information Criterion (AIC). It turns out that the dependence structure among the arms trade flows is complex and can be represented best by a specification that relates each arms trade flow to all exports and imports of the sending and the receiving state. Controlling for exogenous variables, we find that the trade volume increases with the GDP of the sending and the receiving state while the impact of geographical distance, regime dissimilarity and formal alliance membership is rather small.

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Cutright, Phillips, and Robert M. Fernquist. "The Age Structure of Female Suicide Rates: Measurement and Analysis of 20 Developed Countries, 1955–1994." OMEGA - Journal of Death and Dying 47, no. 2 (October 2003): 139–53. http://dx.doi.org/10.2190/yr5v-bkgv-x3rh-kben.

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Although age-specific female suicide rates have been available for over a century, sociologists have focused on comparing the levels of the rates across age groups, and in studying change overtime. Girard's (1993) article is the first systematic effort to compare the age structure of female suicide rates among national populations. From his study of 1976–1980 suicide rates in 49 less developed and more developed populations, Girard concluded that the age structure of female suicide rates was a function of the level of economic development. Our partial test of this theory found that the age structure of female suicide in mid-19th-century European populations was not at all like the structures of less developed countries in 1976–80. We also replaced Girard's qualitative typology with the index of dissimilarity, allowing quantitative assessment of differences between the age structure of suicide in the United States and the other 19 countries in this study. Age structures in 14 countries were significantly different from the U.S. structure. Tests for significant changes in age structures from 1955–64 to 1985–94 found 17 of the 20 populations had significant change in this period, with younger persons tending to increase their share, while persons 45 to 74 were losing their share.

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Yu, Xiangchun, Zhezhou Yu, Wei Pang, Minghao Li, and Lei Wu. "An Improved EMD-Based Dissimilarity Metric for Unsupervised Linear Subspace Learning." Complexity 2018 (2018): 1–24. http://dx.doi.org/10.1155/2018/8917393.

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We investigate a novel way of robust face image feature extraction by adopting the methods based on Unsupervised Linear Subspace Learning to extract a small number of good features. Firstly, the face image is divided into blocks with the specified size, and then we propose and extract pooled Histogram of Oriented Gradient (pHOG) over each block. Secondly, an improved Earth Mover’s Distance (EMD) metric is adopted to measure the dissimilarity between blocks of one face image and the corresponding blocks from the rest of face images. Thirdly, considering the limitations of the original Locality Preserving Projections (LPP), we proposed the Block Structure LPP (BSLPP), which effectively preserves the structural information of face images. Finally, an adjacency graph is constructed and a small number of good features of a face image are obtained by methods based on Unsupervised Linear Subspace Learning. A series of experiments have been conducted on several well-known face databases to evaluate the effectiveness of the proposed algorithm. In addition, we construct the noise, geometric distortion, slight translation, slight rotation AR, and Extended Yale B face databases, and we verify the robustness of the proposed algorithm when faced with a certain degree of these disturbances.

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Rosado, Renato Domiciano Silva, Ana Maria Cruz Oliveira, Iara Gonçalves Santos, Pedro Crescêncio Souza Carneiro, Cosme Damião Cruz, and Paulo Roberto Cecon. "Parental selection based on molecular information under a population genetics approach." Agronomy Science and Biotechnology 7 (May 22, 2021): 1–9. http://dx.doi.org/10.33158/asb.r131.v7.2021.

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The correct choice of parents that will compose optimal segregating populations is the key to success for breeding programs. It was postulated the hypothesis that this choice of these parents could be made based on information of molecular markers analyzed in the context of population structure. Ten parental populations were simulated and 45 hybrid combinations were obtained from the dialel crosses. Each population consisted of 200 individuals with 50 independent loci. The populations were evaluated for the Hardy-Weinberg Equilibrium (HWE), Coefficient of Inbreeding (F), Heterozygosity (H), and the Polymorphic Information Content (PIC). Genetic diversity between pairs of parental populations was evaluated using five dissimilarity measures. Values of Mantel correlation were obtained for the pairs of the dissimilarity matrices, and the PIC, H, and F values were obtained in the hybrid combinations. All parental populations were under HWE, and the combination that emerged from this condition was the hybrid 3x5, with only 26% of the loci manifesting HWE. This same hybrid was among those with lower F estimates and higher values of H, which indicated the existence of greater divergence between their parentals. There was agreement on the indication of the more and less divergent hybrid combinations for the dissimilarity measures. This fact is important because the variability, associated with the good average potential, are important criteria for the formation of an initial population in breeding programs of any kind, involving sexual processes.

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Zhang, Shiwei, Xi Chen, Qiding Zhong, Xuliang Zhuang, and Zhihui Bai. "Microbial Community Analyses Associated with Nine Varieties of Wine Grape Carposphere Based on High-Throughput Sequencing." Microorganisms 7, no. 12 (December 9, 2019): 668. http://dx.doi.org/10.3390/microorganisms7120668.

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Understanding the composition of microbials on the grape carposphere may provide direct guidance for the wine brewing. In this work, 16S rRNA and ITS (Internal Transcribed Spacer) fungal amplicon sequencing were performed to investigate the differences of epiphytic microbial communities inhabiting different varieties of wine grape berries. The results showed that the dominated phylum of different wine grape carpospheres were Proteobacteria, Actinomycetes, Firmicutes, Gemmatimonadete, and Bacteroidetes. The dominant bacterial genera of different wine grape varieties were Pseudomonas, Arthrobacter, Bacillus, Pantoea, Planomicrobium, Massilia, Curtobacterium, Corynebacterium, Cellulomonas, Sphingomonas, and Microvirga. The fungal communities of the grapes were dominated by Ascomycota for all nine wine varieties. The dominant fungal genera on grape carposphere were Alternaria, Cladosporium, unclassified Capnodiales, Phoma, Rhodotorula, Cryptococcus, Aureobasidium, and Epicoccum. Community structure exerts a significant impact on bacterial Bray-Curtis dissimilarity on six red grapes and also a significant bacterial impact on three white grapes. Community structure exerts a significant impact on fungal Bray-Curtis dissimilarity on six red grapes but weak or no fungal impact on three white grapes. The results revealed that grape variety plays a significant role in shaping bacterial and fungal community, varieties can be distinguished based on the abundance of several key bacterial and fungal taxa.

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Soleymani Baghshah, Mahdieh, and Saeed Bagheri Shouraki. "Non-linear metric learning using pairwise similarity and dissimilarity constraints and the geometrical structure of data." Pattern Recognition 43, no. 8 (August 2010): 2982–92. http://dx.doi.org/10.1016/j.patcog.2010.02.022.

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Pereira Martins, Lucas, Anderson Matos Medina, Thomas M. Lewinsohn, and Mário Almeida‐Neto. "The effect of species composition dissimilarity on plant–herbivore network structure is not consistent over time." Biotropica 52, no. 4 (April 13, 2020): 664–74. http://dx.doi.org/10.1111/btp.12791.

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Takemura, Shota, Takashi Takeda, Takayuki Nakanishi, Yukinori Koyama, Hidekazu Ikeno, and Naoto Hirosaki. "Dissimilarity measure of local structure in inorganic crystals using Wasserstein distance to search for novel phosphors." Science and Technology of Advanced Materials 22, no. 1 (April 21, 2021): 185–93. http://dx.doi.org/10.1080/14686996.2021.1899555.

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Cartuche, Alonso, Kalina M. Manoylov, Bastiaan W. Ibelings, and Patrick Venail. "Highest Composition Dissimilarity among Phytoplankton Communities at Intermediate Environmental Distances across High-Altitude Tropical Lakes." Water 13, no. 10 (May 15, 2021): 1378. http://dx.doi.org/10.3390/w13101378.

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Tropical high-altitude lakes are vital freshwater ecosystems for the functioning and dynamics of tropical high-altitude wetlands called páramos, found at over 3300 m above sea level. They play a major role in the hydrogeological cycle and provide important hydrological services such as water storage, and yet they are understudied. Describing the patterns and processes of community composition in these lakes is required to better understand the consequences of their degradation by human activities. In this study we tested the geographical and environmental components of distance–decay relationships in the phytoplankton structure across 24 tropical high-altitude lakes from Southern Ecuador. Phytoplankton composition at the phyla level showed high among-lake variation in the tropical high-altitude lakes from Tres Lagunas. We found no links, however, between the geographic distance and phytoplankton composition. On the contrary, we observed some environmentally related patterns of community structure like redox potential, altitude, water temperature, and total phosphorus. The absence of support for the distance–decay relationship observed here can result from a conjunction of local niche-based effects and dispersal limitations. Phytoplankton community composition in the Tres Lagunas system or any other ecosystem may be jointly regulated by niche-based and neutral forces that still need to be explored. Despite not proving a mechanistic explanation for the observed patterns of community structure, we hope our findings provide understanding of these vulnerable and vital ecosystems. More studies in tropical high-altitude lakes are urgently required.

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Garzón, Benjamín, Martin Lövdén, Lieke de Boer, Jan Axelsson, Katrine Riklund, Lars Bäckman, Lars Nyberg, and Marc Guitart-Masip. "Role of dopamine and gray matter density in aging effects and individual differences of functional connectomes." Brain Structure and Function 226, no. 3 (January 9, 2021): 743–58. http://dx.doi.org/10.1007/s00429-020-02205-4.

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AbstractWith increasing age, functional connectomes become dissimilar across normal individuals, reflecting heterogenous aging effects on functional connectivity (FC). We investigated the distribution of these effects across the connectome and their relationship with age-related differences in dopamine (DA) D1 receptor availability and gray matter density (GMD). With this aim, we determined aging effects on mean and interindividual variance of FC using fMRI in 30 younger and 30 older healthy subjects and mapped the contribution of each connection to the patterns of age-related similarity loss. Aging effects on mean FC accounted mainly for the dissimilarity between connectomes of younger and older adults, and were related, across brain regions, to aging effects on DA D1 receptor availability. Aging effects on the variance of FC indicated a global increase in variance with advancing age, explained connectome dissimilarity among older subjects and were related to aging effects on variance of GMD. The relationship between aging and the similarity of connectomes can thus be partly explained by age differences in DA modulation and gray matter structure.

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Foote, Mike. "Early morphological diversity in blastozoan echinoderms." Paleontological Society Special Publications 6 (1992): 102. http://dx.doi.org/10.1017/s2475262200006626.

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Morphological diversity (MD) is important for understanding a clade's evolution and for comparing clades to discover evolutionary laws. As the scale of analysis (taxonomic rank) increases, defining a morphological space becomes less tractable, and assessing MD becomes more difficult. Continuous morphometric variables are hard to define for very disparate species, but morphological dissimilarity can be assessed by discrete characters. I use this approach to document the history of MD in the echinoderm subphlylum Blastozoa.About 60 discrete characters were defined, relating to: arrangement and number of thecal plates; shape and symmetry of theca; number, arrangement, form, and plating of ambulacra; arrangement, form, and plating of brachioles; form and plating of attachment structure; nature of respiratory structures; and position of mouth and anus. Character difference for binary and unordered multistate characters is 0 for matches and 1 for mismatches. Ordered multistate characters were scaled so that the maximum character difference was unity. Pairwise dissimilarity between species was measured by the mean character difference. MD in a stratigraphic interval was measured by the mean pairwise dissimilarity among species. Over half of all described genera were represented. MD involves not only the origin of new character states but also the maintenance of primitive states in a clade; therefore, assessment of MD was deliberately not restricted to analysis of novelties! The figures below compare MD to generic diversity based on the Treatise and post-Treatise monographs.Debate persists about the nature and extent of early echinoderm diversification. Most pertinent to this debate, MD in the Cambrian and Lower Ordovician is extremely high compared to taxonomic diversity; there are few taxa sparsely occupying much morphospace. Analysis of clade-shape statistics indicates that the blastozoan clade is bottom-heavy in both aspects of diversity, but more so with respect to MD. The results overall are not sensitive to the details of the time scale, the inclusion of problematic forms, or the number of characters used. The general picture agrees with that advocated by Sprinkle (among others) for the echinoderms as a whole.

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Journal articles on the topic 'Structure dissimilarity'

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