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Isolated Position (isolated + position)
Selected AbstractsThe fellowship of the hobbit: the fauna surrounding Homo floresiensisJOURNAL OF BIOGEOGRAPHY, Issue 6 2010Hanneke J. M. Meijer Abstract The Late Pleistocene Flores fauna shows a pattern observed on many other islands. It is neither aberrant nor exclusive, but the result of non-random selective forces acting upon an impoverished and disharmonic insular fauna. By comparing the Flores vertebrate fauna with other fossil insular biotas, it is apparent that the evolution of Homo floresiensis is part of a general pattern affecting all the inhabitants of Pleistocene Flores. Vertebrate evolution on Flores appears to have been characterized by phylogenetic continuity, low species richness and a disharmonic fauna. All three aspects stem from the isolated position of the island and have resulted in the distinct morphological characteristics of the Flores fauna. Evidence reviewed herein shows that features exhibited by H. floresiensis, such as small stature, a small brain, relatively long arms, robust lower limbs and long feet, are not unique, but are shared by other insular taxa. Therefore, the evolution of H. floresiensis can be explained by existing models of insular evolution and followed evolutionary pathways similar to those of the other terrestrial vertebrates inhabiting Pleistocene Flores. [source] Morphological and Molecular Characterization of a New Protist Family, Sandmanniellidae n. fam. (Ciliophora, Colpodea), with Description of Sandmanniella terricola n. g., n. sp. from the Chobe Floodplain in BotswanaTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 5 2009WILHELM FOISSNER ABSTRACT. Sandmanniella terricola n. g., n. sp. was discovered in soil from the Chobe floodplain, Botswana, southern Africa. Its morphology and 18S rDNA gene sequence were studied with standard methods. Sandmanniella terricola is very likely an adversity strategist because it reaches peak abundances 6,12 h after rewetting the soil and maintains trophic food vacuoles with undigested bacteria in the resting cyst, a highly specific feature suggested as an indicator for an adversity life strategy. Possibly, the energy of the stored food vacuoles is used for reproduction and support of the cyst wall. Morphologically, Sandmanniella terricola is inconspicuous, having a size of only 50 × 40 ,m and a simple, ellipsoidal shape. The main characteristics of the genus are a colpodid silverline pattern; a perioral cilia condensation; a flat, dish-shaped oral cavity, in the centre of which originates a long, conical oral basket resembling that of certain nassulid ciliates; and a vertically oriented left oral polykinetid composed of brick-shaped adoral organelles. This unique mixture of features and the gene sequence trees, where Sandmanniella shows an isolated position, suggest establishing a new family, the Sandmanniellidae n. fam., possibly related to the families Colpodidae or Bryophryidae. The curious oral basket provides some support for the hypothesis of a common ancestor of colpodid and nassulid ciliates. [source] Systematic significance of fruit morphology and anatomy in tribes Persicarieae and Polygoneae (Polygonaceae)BOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1-2 2000LOUIS P. RONSE DECRAENE FLS Fruits of Polygonaceae have a basically similar construction of indchiscent nuts or achencs. Sections of fruits, coupled with surface patterns were studied with SEM and LM in all genera of the tribes Persicarieae and Polygoneae (Polygonoidcae-Polvgonaceae). The outer layer of the pericarp is usually thickened and its anatomy can be used consistently to delimit genera more than any other character of the fruit. Cells are most often puzzle piece-shaped in surface view, but the shape of the cells may become polygonal with straight anticlinal walls towards the endocarp. The primary sculpture of the cells is highly yariable and has value at the specific level, rarely at the generic level. No strict correlation exists between the external surface patterns and the anatomy. Two main cell types can be recognized in cross- and longitudinal section, correlated with the straight or undulating outline of the anticlinal walls. No distinction can be made between sections Persicaria, Tovara, Echinocaulon, and Cephalophtlon of the genus Persicaria: all share narrow rectangular cells with undulating anticlinal walls. Aconogonon and Bistorta can be delimited by the square to rectangular cells with a narrow dichotomously branching lumen and straight anticlinal walls; both genera are best grouped as a single genus with two sections. A similar arrangement is found occasionally in species of Polygonum s.s. Polygonella. Atraphaxis. Faltopia and Calligonum. Fruit anatomy of Pteropyrum is distinctive. The genus Polygonum s.s. shows a wide range of integrating patterns, ranging from straight to undulating anticlinal walls and cannot be separated from Polygonella. Fagopyrum is aberrant in having a parenchymatic exocarp and a thickened mesocarp: other evidence supports its isolated position. Different fruit anatomical patterns have arisen several times in evolution and have a limited value at tribal level but are useful at generic level. It is suggested that an arrangement with straight anticlinal walls and a broad lumen, eventually with dendritic branching towards the periphery, is ancestral. [source] Infection-associated type IV secretion systems of Bartonella and their diverse roles in host cell interactionCELLULAR MICROBIOLOGY, Issue 8 2008Christoph Dehio Summary Type IV secretion systems (T4SSs) are transporters of Gram-negative bacteria that mediate interbacterial DNA transfer, and translocation of virulence factors into eukaryotic host cells. The ,-proteobacterial genus Bartonella comprises arthropod-borne pathogens that colonize endothelial cells and erythrocytes of their mammalian reservoir hosts, thereby causing long-lasting intraerythrocytic infections. The deadly human pathogen Bartonella bacilliformis holds an isolated position in the Bartonella phylogeny as a sole representative of an ancestral lineage. All other species evolved in a separate ,modern' lineage by radial speciation and represent highly host-adapted pathogens of limited virulence potential. Unlike B. bacilliformis, the species of the modern lineage encode at least one of the closely related T4SSs, VirB/VirD4 or Vbh. These VirB-like T4SSs represent major host adaptability factors that contributed to the remarkable evolutionary success of the modern lineage. At the molecular level, the VirB/VirD4 T4SS was shown to translocate several effector proteins into endothelial cells that subvert cellular functions critical for establishing chronic infection. A third T4SS, Trw, is present in a sub-branch of the modern lineage. Trw does not translocate any known effectors, but produces multiple variant pilus subunits critically involved in the invasion of erythrocytes. The T4SSs laterally acquired by the bartonellae have thus adopted highly diverse functions during infection, highlighting their versatility as pathogenicity factors. [source] | ||||||||||