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Several Characters (several + character)
Selected AbstractsAnatomy and systematics of the minute syrnolopsine gastropods from Lake Tanganyika (Caenogastropoda, Cerithioidea, Paludomidae)ACTA ZOOLOGICA, Issue 4 2008Ellen E. Strong Abstract The minute syrnolopsine gastropods endemic to Lake Tanganyika have been allied to a number of freshwater, marine and terrestrial groups as a consequence of superficial conchological similarity. Although early anatomical studies confirmed the cerithioid organization of this clade, their close relationship to other lake species was not consistently recognized. In several recent cladistic analyses based on molecular data, the higher taxonomic placement and sister group relationships of syrnolopsines have been unstable. The present analysis confirms that syrnolopsines possess a spermatophore-forming organ , a synapomorphy of the Paludomidae , corroborating their placement in this family. Consistent with the molecular data, syrnolopsine monophyly is supported by two characters that occur exclusively in this group (salivary gland ducts that bypass the nerve ring and a linear albumen gland). Several characters in Martelia tanganyicensis, the most diminutive syrnolopsine , are only evident in the smallest lake species thus far investigated (Bridouxia, Stormsia) namely reduction of ctenidial leaflets, sorting area, intestine length and number of statoconia. These features are interpreted as being correlated with reduction in size. Nevertheless, close examination reveals differences in detail that allow more refined hypotheses of homology and are consistent with their independent origin. [source] Pretarsal structures in Reduviidae (Heteroptera, Ins ecta)ACTA ZOOLOGICA, Issue 2 2005Christiane Weirauch Abstract A survey of pretarsal structures in Reduviidae of 22 higher-level taxa and several outgroup representatives is conducted using scanning electron microscopy (SEM) and light microscopy. Based on histology and SEM, pretarsal structures are described in detail for Rhodnius prolixus. Structures of the distal tarsomer, which appear to be functionally correlated with the pretarsus, are documented for the first time in Heteroptera. These comprise lateral oval sclerites, two campaniform sensilla and two marginal setae, observed in Reduviidae and other heteropteran taxa. The presence of a peg-like dorsomedian sensillum medially between the claws in Reduviidae and Nabidae is demonstrated. As a result of its structure and position, homology of this sensillum with the ,dorsal arolium' in other heteropteran groups is proposed. Within Reduviidae, the transformation of the peg-like dorsomedian sensillum to a campaniform sensillum, as seen in most representatives of the harpactoroid complex, is hypothesized. The first record of parempodia other than setiform within Reduviidae is noted in nymphs of Harpactorinae, which may possess lamellate parempodia. Several characters that are possibly useful for clarifying relationships among the harpactoroid groups are described and discussed. The pretarsal structures, including the unguitractor plate and the tarsal marginal setae among reduviid groups are discussed in a phylogenetic context. [source] A morphological reappraisal of Tubifex blanchardi Vejdovský, 1891 (Clitellata: Tubificidae)ACTA ZOOLOGICA, Issue 2 2009Roberto Marotta Abstract Tubifex blanchardi Vejdovský, 1891 is a freshwater tubificid, often living in sympatry with Tubifex tubifex (Müller 1774). Although considered from its discovery as a species on its own, its biological status is debated. During the early seventies T. blanchardi was reduced to a mere form of T. tubifex, as a particular case of polymorphism in chaetal pattern. Using classical histological techniques, microdissections of portions of the male genital apparatus and phalloidin staining of dissected copulatory organs we investigated 163 mixed individuals of T. blanchardi and T. tubifex belonging to sympatric populations from the Lambro River (Milan, Northern Italy). The internal morphology of T. blanchardi is described for the first time. Our results show that T. tubifex and T. blanchardi differ in several characters concerning both their external and internal morphology, and in the fine organization of their copulatory organs. Several independent character sets support the separation of T. blanchardi from T. tubifex, suggesting that it is an independent species. This study also supports the idea that T. blanchardi and T. bergi (Hrab,, 1935), another species closely related to T. tubifex, are not conspecific. The observed morphological differences between allopatric populations of T. tubifex are discussed. [source] Use of paleontological and molecular data in supertrees for comparative studies: the example of lissamphibian femoral microanatomyJOURNAL OF ANATOMY, Issue 2 2009Michel Laurin Abstract A new method to assemble time-calibrated supertrees is able to incorporate paleontological and molecular dates. This method, along with new branch length transformations, is implemented in the Stratigraphic Tools for Mesquite. It was used here to analyse a dataset on bone microanatomy, body size and habitat of 46 species of lissamphibians through a variety of methods (Felsenstein independent contrasts, variance partition with phylogenetic eigenvector regression, discriminant analyses and simple regressions). Our analyses showed that the new methods can produce adequate standardization for several characters on a tree whose branch lengths can represent evolutionary time. The analyses confirmed previous conclusions about the presence of an ecological signal in bone microanatomical data. [source] Genome size and recombination in angiosperms: a second lookJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2007J. ROSS-IBARRA Abstract Despite dramatic differences in genome size , and thus space for recombination to occur , previous workers found no correlation between recombination rate and genome size in flowering plants. Here I re-investigate these claims using phylogenetic comparative methods to test a large data set of recombination data in angiosperms. I show that genome size is significantly correlated with recombination rate across a wide sampling of species and that change in genome size explains a meaningful proportion (,20%) of variation in recombination rate. I show that the strength of this correlation is comparable with that of several characters previously linked to evolutionary change in recombination rate, but argue that consideration of processes of genome size change likely make the observed correlation a conservative estimate. And finally, although I find that recombination rate increases less than proportionally to change in genome size, several mechanistic and theoretical arguments suggest that this result is not unexpected. [source] Morphometric convergence and molecular divergence: the taxonomic status and evolutionary history of Gymnura crebripunctata and Gymnura marmorata in the eastern Pacific OceanJOURNAL OF FISH BIOLOGY, Issue 4 2009W.D. Smith To clarify the taxonomic status of Gymnura crebripunctata and Gymnura marmorata, the extent of morphological and nucleotide variation between these nominal species was examined using multivariate morphological and mitochondrial DNA comparisons of the same characters with congeneric species. Discriminant analysis of 21 morphometric variables from four species (G. crebripunctata, G. marmorata, Gymnura micrura and Gymnura poecilura) successfully distinguished species groupings. Classification success of eastern Pacific species improved further when specimens were grouped by species and sex. Discriminant analysis of size-corrected data generated species assignments that were consistently accurate in separating the two species (100% jackknifed assignment success). Nasal curtain length was identified as the character which contributed the most to discrimination of the two species. Sexual dimorphism was evident in several characters that have previously been relied upon to distinguish G. crebripunctata from G. marmorata. A previously unreported feature, the absence of a tail spine in G. crebripunctata, provides an improved method of field identification between these species. Phylogenetic and genetic distance analyses based on 698 base pairs of the mitochondrial cytochrome b gene indicate that G. crebripunctata and G. marmorata form highly divergent lineages, supporting their validity as distinct species. The closely related batoid Aetoplatea zonura clustered within the Gymnura clade, indicating that it may not represent a valid genus. Strong population structuring (overall ,ST = 0·81,P < 0·01) was evident between G. marmorata from the Pacific coast of the Baja California peninsula and the Gulf of California, supporting the designation of distinct management units in these regions. [source] PHYLOGENETIC RELATIONSHIP OF COLEOCHAETE AND CHAETO-SPHAERIDIUM (COLEOCHAETALES) BASED ON THE CHLOROPLAST GENES RBCL AND ATPBJOURNAL OF PHYCOLOGY, Issue 2000Cimino M. T. The freshwater green algal genera Coleochaete and Chaetosphaeridium form the order Coleochaetales sensu Mattox and Stewart (Charophyceae). To test the monophyly of this order, a data set was compiled consisting of the chloroplast genes rbcL and atpB from nine species of Coleochaete, six strains of Chaetosphaeridium, and other representative green algae and embryophytes. Phylogenetic analyses of these data indicate that Coleochaete and Chaetosphaeridium form a monophyletic group that diverged late in basal streptophyte evolution. By contrast, published analyses of nuclear encoded small subunit ribosomal DNA (rDNA) data for similar taxa do not support a monophyletic Coleochaetales. These analyses suggest Chaetosphaeridium is an early branching lineage within Streptophyta and/or that Chaetosphaeridium forms a lineage with the unicellular flagellate Mesostigma (Mesostigmatophyceae). A close relationship of Chaetosphaeridium and Mesostigma is not supported by the rbcL and atpB data. Reexamination of morphological characters suggests a monophyletic Coleochaetales is supported by several characters that include branching filamentous habit, unicellular apical growth, sheathed hairs, and rotating plastids. [source] A Relict Rhinesuchid (Amphibia: Temnospondyli) From The Lower Triassic Of South AfricaPALAEONTOLOGY, Issue 4 2000M. A. Shishkin ,Lydekkerina'putterilli Broom from the Lystrosaurus Assemblage Zone (Middle Beaufort Group, South Africa) is shown to be a paedomorphic rhinesuchid (Broomistega putterilli gen. nov.) rather than a lydekkerinid or juvenile stage of the rhinesuchid Uranocentrodon, as previously presumed. The most conspicuous characters, not related to its paedomorphic condition, include the shape of the parietals and the structure of the parasphenoid body and exoccipitals. The pattern of cranial growth changes in Broomistega has been investigated by comparison of the holotype with two hitherto undescribed immature specimens. For several characters referring to the size and position of the orbits, and re-modelling of the jugal proportions, retarded timing of growth transformations, compared to ontogenetic patterns in Permian rhinesuchids (typified by Muchocephalus) is demonstrated. Some features of the evolution of the basicranial region of the skull, in the transition from rhinesuchids to more advanced capitosauroids, are re-evaluated. key words: temnospondyls, rhinesuchids, relict, paedomorphosis, growth changes. [source] Phylogeny of Nerillidae (Polychaeta, Annelida) as inferred from combined 18S rDNA and morphological dataCLADISTICS, Issue 2 2005Katrine Worsaae A phylogeny of the meiofaunal polychaete family Nerillidae based on morphological, molecular and combined data is presented here. The data sets comprise nearly complete sequences of 18S rDNA and 40 morphological characters of 17 taxa. Sequences were analyzed simultaneously with the morphological data by direct optimization in the program POY, with a variety of parameter sets (costs of gaps: transversions: transitions). Three outgroups were selected from the major polychaete group Aciculata and one from Scolecida. The 13 nerillid species from 11 genera were monophyletic in all analyses with very high support, and three new apomorphies for Nerillidae are identified. The topology of the ingroup varied according to the various parameter settings. Reducing the number of outgroups to one decreased the variance among the phylogenetic hypotheses. The congruence among these was tested and a parameter set, with equal weights (222) and extension gap weighted 1, yielded minimum incongruence (ILD). Several terminal clades of the combined analysis were highly supported, as well as the position of Leptonerilla prospera as sister terminal to the other nerillids. The evolution of morphological characters such as segment numbers, chaetae, appendages and ciliation are traced and discussed. A regressive pathway within Nerillidae is indicated for several characters, however, generally implying several convergent losses. Numerous genera are shown to require revision. © The Willi Hennig Society 2005. [source] | |||||||||||||