Character selection in relation to the numerical taxonomy of some male Diaspididae (Homoptera: Coccoidea)

A quantitative comparison of the classifications of 24 species of male Diaspididae by principal component and principal coordinate analysis was extended to allow the comparison of classifications based on selected subsets of the 101 available characters. It was shown that subsets of 25–28 characters could be chosen numerically and used to construct classifications that resembled very closely the classification based on the reference set of characters. The conclusions are discussed in relation to other views on character-weighting and in relation to classifications of the Diaspididae based on traditional taxonomic characters provided by the females.     

Evaluating the stability of the classification of community data

We propose a method for a posteriori evaluation of classification stability which compares the classification of sites in the original data set (a matrix of species by sites) with classifications of subsets of its sites created by without‐replacement bootstrap resampling. Site assignments to clusters of the original classification and to clusters of the classification of each subset are compared using Goodman‐Kruskal's lambda index. Many resampled subsets are classified and the mean of lambda values calculated for the classifications of these subsets is used as an estimation of classification stability. Furthermore, the mean of the lambda values based on different resampled subsets, calculated for each site of the data set separately, can be used as a measure of the influence of particular sites on classification stability. This method was tested on several artificial data sets classified by commonly used clustering methods and on a real data set of forest vegetation plots. Its strength lies in the ability to distinguish classifications which reflect robust patterns of community differentiation from unstable classifications of more continuous patterns. In addition, it can identify sites within each cluster which have a transitional species composition with respect to other clusters.     

Phylogenetic analyses of morphological evolution in the gametophyte and sporophyte generations of the moss order Hookeriales (Bryopsida)

Morphological characters from the gametophyte and sporophyte generations have been used in land plants to infer relationships and construct classifications, but sporophytes provide the vast majority of data for the systematics of vascular plants. In bryophytes both generations are well developed and characters from both are commonly used to classify these organisms. However, because morphological traits of gametophytes and sporophytes can have different genetic bases and experience different selective pressures, taxonomic emphasis on one generation or the other may yield incongruent classifications. The moss order Hookeriales has a controversial taxonomic history because previous classifications have focused almost exclusively on either gametophytes or sporophytes. The Hookeriales provide a model for comparing morphological evolution in gametophytes and sporophytes, and its impact on alternative classification systems. In this study we reconstruct relationships among mosses that are or have been included in the Hookeriales based on sequences from five gene regions, and reconstruct morphological evolution of six sporophyte and gametophyte traits that have been used to differentiate families and genera. We found that the Hookeriales, as currently circumscribed, are monophyletic and that both sporophyte and gametophyte characters are labile. We documented parallel changes and reversals in traits from both generations. This study addresses the general issue of morphological reversals to ancestral states, and resolves novel relationships in the Hookeriales.     

Phylogeny and classification of the Catantopidae at the tribal level (Orthoptera, Acridoidea)

The grasshopper family Catantopidae is a well-known group, whose members include some of the most notorious agricultural pests. The existing classifications of the family are mostly utilitarian rather than being based on phylogenetic analysis and therefore unable to provide the stability desired for such an economically important group. In the present study, we present the first comprehensive phylogenetic analysis of the family based on morphology. By extensively sampling from the Chinese fauna, we included in the present analysis multiple representatives of each of the previously recognized tribes in the family. In total, we examined 94 genera represented by 240 species and evaluated 116 characters, including 84 for external morphology and 32 for male genitalia. The final matrix consists of 86 ingroup taxa and 88 characters. Our phylogenetic analyses resulted in a high resolution of the basal relationships of the family while showed considerable uncertainty about the relationships among some crown taxa. We further evaluated the usefulness of morphological characters in phylogeny reconstruction of the catantopids by examining character fit to the shortest trees found, and contrary to previous suggestions, our results suggest that genitalia characters are not as informative as external morphology in inferring higher-level relationship. We further suggest that earlier classification systems of grasshoppers in general and Catantopidae in particular most probably consist of many groups that are not natural due the heavy reliance on genitalia features and need to be revised in the light of future phylogenetic studies. Finally, we outlined a tentative classification scheme based on the results of our phylogenetic analysis.     

Phylogenetics and evolution of Capitata (Cnidaria: Hydrozoa), and the systematics of Corynidae

Nawrocki, A. M., Schuchert, P. & Cartwright, P. (2009). Phylogenetics and evolution of Capitata (Cnidaria: Hydrozoa), and the systematics of Corynidae.—Zoologica Scripta, 39, 290–304. Generic‐ and family level classifications in Hydrozoa have been historically problematic due to limited morphological characters for phylogenetic analyses and thus taxonomy, as well as disagreement over the relative importance of polyp vs. medusa characters. Within the recently redefined suborder Capitata (Cnidaria: Hydrozoa: Hydroidolina), which includes 15 families and almost 200 valid species, family level relationships based on morphology alone have proven elusive, and there exist numerous conflicting proposals for the relationships of component species. Relationships within the speciose capitate family Corynidae also remain uncertain, for similar reasons. Here, we combine mitochondrial 16S, and nuclear 18S and 28S sequences from capitate hydrozoans representing 12 of the 15 valid capitate families, to examine family level relationships within Capitata. We further sample densely within Corynidae to investigate the validity of several generic‐level classification schemes that rely heavily on the presence/absence of a medusa, a character that has been questioned for its utility in generic‐level classification. We recover largely congruent tree topologies from all three markers, with 28S and the combined dataset providing the most resolution. Our study confirms the monophyly of the redefined Capitata, and provides resolution for family level relationships of most sampled families within the suborder. These analyses reveal Corynidae as paraphyletic and suggest that the limits of the family have been underestimated. Our results contradict all available generic‐level classification schemes for Corynidae. As classification schemes for this family have been largely based on reproductive characters such as the presence/absence of a medusa, our results suggest that these are not valid generic‐level characters for the clade. We suggest a new taxonomic structure for the lineage that includes all members of the newly redefined Corynidae, based on molecular and morphological synapomorphies for recovered clades within the group.     

A Re-assessment of Relationships within Epacridaceae

An extensive database of predominantly morphological characters has been assembled for the family Epacridaceae. Problems of homology across the family and its outgroups were encountered for several characters. A phylogenetic analysis, using only those characters for which we were fairly confident of our assessment of homology, was undertaken to establish broad relationships within the family as a basis for a re-assessment of the supra-generic classification. The resultant phylogeny is weakly resolved and lacks robustness in the basal clades. Previous classifications of the family are assessed in the light of this analysis, and an alternative arrangement of four tribes is proposed.     

The road to the Janiroidea: Comparative morphology and evolution of the asellote isopod crustaceans

This paper presents a new phylogenetic estimate of isopod crustaceans of the suborder Asellota with the aim of clarifying the evolution of the superfamily Janiroidea, a large and diverse group inhabiting all aqueous habitats. The phylogenetic analysis is based on a morphological evaluation of characters used in past classifications, as well as several new characters. The evolutionary polarity of the characters was determined by outgroup analysis. The characters employed were from the pleopods, the copulatory organs, the first walking legs, and the cephalon. The resulting character data set was analyzed with numerical phylogenetic computer programs to find one most parsimonious clado-gram, which is translated into a classification using the sequencing convention. The new phylogenetic estimate is significantly more parsimonious than previous trees from the literature, and several of its monophyletic groups have robust confidence limits. The superfamily Stenetrioidea belongs to the clade including the Janiroidea, not with the Aselloidea as previously suggested. The sister group of the Janiroidea is the family Pseudojaniridae, which is elevated to superfamily rank. The clade including the families Gnathostenetroididae and Protojaniridae is not the sister group of the Janiroidea, and is derived earlier in janiroidean evolution than the Stenetrioidea. Within the Janiroidea, the family Janiridae is not the most primitive taxon as previously believed. The clade including the families Munnidae and Pleurocopidae contains the earliest derived janiroideans. The data also indicate that the unusual sexual morphology of the Janiroidea did not appear suddenly but developed as a series of independent steps within the Asellota.     

A Representational Similarity Analysis of the Dynamics of Object Processing Using Single-Trial EEG Classification

The recognition of object categories is effortlessly accomplished in everyday life, yet its neural underpinnings remain not fully understood. In this electroencephalography (EEG) study, we used single-trial classification to perform a Representational Similarity Analysis (RSA) of categorical representation of objects in human visual cortex. Brain responses were recorded while participants viewed a set of 72 photographs of objects with a planned category structure. The Representational Dissimilarity Matrix (RDM) used for RSA was derived from confusions of a linear classifier operating on single EEG trials. In contrast to past studies, which used pairwise correlation or classification to derive the RDM, we used confusion matrices from multi-class classifications, which provided novel self-similarity measures that were used to derive the overall size of the representational space. We additionally performed classifications on subsets of the brain response in order to identify spatial and temporal EEG components that best discriminated object categories and exemplars. Results from category-level classifications revealed that brain responses to images of human faces formed the most distinct category, while responses to images from the two inanimate categories formed a single category cluster. Exemplar-level classifications produced a broadly similar category structure, as well as sub-clusters corresponding to natural language categories. Spatiotemporal components of the brain response that differentiated exemplars within a category were found to differ from those implicated in differentiating between categories. Our results show that a classification approach can be successfully applied to single-trial scalp-recorded EEG to recover fine-grained object category structure, as well as to identify interpretable spatiotemporal components underlying object processing. Finally, object category can be decoded from purely temporal information recorded at single electrodes.     

Limb myology and phylogenetic relationships in the superfamily Dipodoidea (birch mice, jumping mice, and jerboas)

Limb muscles were dissected in seven genera, representing all six superfamilies, of dipodoid rodents and myoloic characters were used to construct a phylogenetic hpothesis of relationships within this cfade. Mologic differences among genera suported tie monophyly of the superfamily Dipodoidea reLtive to the outrou taxon and reveaEd thatSicista is the sister group to all other zapodid and dipodid enera. Tkis picement of Sicista differs markedly from its position in previous classifications where it has been regarded merely as a primitive zapodid genus. The phlograrn based on rnyologic characters also indicated that Cardiocranius is not a rimitive dipodid genus; it is the sister group to the subfamily Dipodinae. Although myologic differences among taxa were not sufficient to warrant the continued separation of zaodids and dipodids into two families, a new classification that places Sicista in its own family, ficistidae, and places the remaining zaodids and dipodids in the family Dipodidae, is proposed. Differences in karyology, genitaP morholoy, and postcranial osteological characters among dipodoid rodents are discussed in light or this pjylogeny.     

A comparison of DNA‐based methods for delimiting species in a Cretan land snail radiation reveals shortcomings of exclusively molecular taxonomy

We compared the results of different approaches for delimiting species based on single‐locus DNA sequences with those of methods using binary multilocus data. As case study, we examined the radiation of the land snail genus Xerocrassa on Crete. Many of the methods based on mitochondrial sequences resulted in heavy under‐ or overestimations of the species number. The methods using AFLP data produced classifications with an on average higher concordance with the morphological classification than the methods based on mitochondrial sequences. However, the percentage of correct species classifications is low even with binary multilocus data. Gaussian clustering produced the classifications with the highest concordance with the morphological classification of all approaches applied in this study, both with single‐locus sequences and with binary multilocus data. There are two general problems that hamper species delimitation, namely rarity and the hierarchical structure of biodiversity. Methods for species delimitation using genetic data search for clusters of individuals, but do not implement criteria that are sufficient to distinguish clusters representing species from other clusters. The success of morphological species delimitation results from the potential to focus on characters that are directly involved in the speciation process, whereas molecular studies usually rely on markers that are not directly involved in speciation. © The Willi Hennig Society 2011.     

Comparison of floristic and structural classification of vegetation

A comparison is made between floristic and structural-physiognomic classifications of a tropical dry, semi-evergreen forest and thicket vegetation of south-eastern India. The classifications are strikingly similar in their main groupings which are ecologically meaningful; the differences between the classifications are virtually limited to allocation of some stands to different subcommunities. It is concluded that the use of structural-physiognomic criteria allows a detailed and ecologically significant classification of vegetation. Fairly advanced calculation facilities are necessary, however, to reach such a classification, since the structural-physiognomic differences between the resulting groupings are largely of a quantitative and not of a qualitative nature. This is a consequence of the general occurrence in all stands of the vegetation of the very great majority of the characters used in this study.Nomenclature follows Sprangers & Balasubramanian (1978) who give a complete list of authorities.     

Molecular phylogeny of the family Pectinidae (Mollusca: Bivalvia) based on mitochondrial 16S and 12S rRNA genes

Pectinidae is a large bivalve family characterised by almost circular, flat shells. Species are distributed worldwide and fall into three life-styles: swimming, byssally attached to hard substrates, and cemented to rocks with one valve. Despite these very different life strategies, pectinid shells are highly conservative in shape and offer few clues for the unravelling of phylogenetic issues. Consequently, phylogenetic studies based on morphological features have not yielded conclusive results. We thus set out to analyse partial sequences of mitochondrial 12S and 16S rRNA genes from 23 species of 16 genera with molecular techniques. The results are largely in contrast, both at the genus and the subfamily level, with the systematic classifications based on adult morphological characters, whereas they agree with the morphological classifications based on the more conserved non-adaptive features.