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In Ergänzung zu früheren Veröffentlichungen (z. B. Pedersen & Weber 1993) wird eine aktualisierte Übersicht über die Brombeerflora (Rubus L. subgen. Rubus) von Niedersachsen und Bremen gegeben. Bis jetzt sind 169 Arten der Sektionen Rubus und Corylifolii in diesem Gebiet nachgewiesen. Davon gehören 117 zur Sektion Rubus und 52 zur Sektion Corylifolii. Fünf Arten der Sektion Rubus sind Gartenflüchtlinge und inzwischen völlig eingebürgert: Rubus allegheniensis, R. armeniacus, R. canadensis und R. laciniatus. Selten und zufällig eingeschleppt wurden Rubus bifrons und R. ulmifolius. Somit besteht die Brombeerflora in Niedersachsen und Bremen aus 162 einheimischen Arten, von denen 52 (= 32%) zur Sektion Corylifolii gehören.
Die Verlandungsvegetation des Dümmers wurde seit Beginn des 20. Jahrhunderts mehrfach untersucht. 2006 erfolgte erstmals eine flächendeckende Kartierung der gesamten Verlandungszone. Seit der 1953 abgeschlossenen Eindeichung war diese massiven Veränderungen unterworfen. Bereits kurz nach Deichschluss kam es zu einer massiven Reduktion der seeseitigen, durchfluteten Schilfbestände (Phragmites australis). Weite Röhrichtpartien entwickelten sich zunächst zu Wasserschwaden-Beständen (Glyceria maxima), dann wieder zu Schilfröhrichten. Nach einer zwischenzeitlichen Stagnation der Röhrichtabbrüche in den 1980er Jahren kam es in den letzten 15-20 Jahren zu erneuten erheblichen Flächenverlusten. Die ehemals typischen Teichbinseninseln (Schoenoplectus spp.) sind inzwischen weitestgehend verschwunden. Die Wasserrosenfelder (Nuphar lutea, Nymphaea alba) verloren seit den 1990er Jahren erheblich an Fläche. Alle Verluste an der Verlandungsvegetation dürften zunächst durch die Gewässerbelastung, in neuerer Zeit vor allem durch zu hoch gehaltene Sommerwasserstände verursacht sein. Die ehemals üppige und artenreiche submerse Vegetation starb nach der Eindeichung vollständig ab. Nach einer unerwartet eingetretenen Klarwasserphase wurde 2001 erstmals wieder Potamogeton pectinatus nachgewiesen, seitdem wurden weitere Laichkraut-Arten, zwei Arten der Armleuchteralgen (Chara fragilis, Nitella mucronata) und weitere Tauch- und Schwimmblattpflanzen nachgewiesen. Die voraussichtlich 2009 erfolgende Umleitung des Bornbaches, über den ein Großteil der heutigen Nährstofffracht in den Dümmer gelangt, dürfte die Bedingungen für die submerse Vegetation entscheidend verbessern.
Linyphia triumphalis Denis, 1952 was found to be a junior synonym of Centromerus pabulator (O.P.-Cambridge, 1875) (Araneae, Linyphiidae). New synonymy.
A glimpse of the tropics : spiders (Araneae) in the greenhouses of the Botanic Garden Berlin-Dahlem
(2008)
In a survey of the spider fauna in greenhouses of the Botanic Garden Berlin-Dahlem, 30 spider species were recorded. Two species are new to Europe: Theotima minutissima (Petrunkevitch, 1929) and Heteroonops spinimanus (Simon, 1891). T. minutissima is the first member of the family Ochyroceratidae reported from Europe. Oecobius navus Blackwall, 1859 is new to Central Europe. Triaeris stenaspis Simon, 1891, is recorded from Germany for the first time. Zodarion italicum (Canestrini, 1868) is new to eastern Germany. Despite the discovery of some species previously unknown to Germany, the spider fauna in the Botanic Garden consisted mainly of wellknown synanthropic species and common inhabitants of greenhouses. Several alien spiders recently found in greenhouses, garden centers and houses were not recorded in the Botanic Garden. The species composition of the exotic spider fauna in greenhouses seems to depend chiefly on the specific modes of acquisition of plants and plant substrate.
In the course of a long term survey on the effects of grazing on the diversity of alpine grasslands, the false scorpion Chthonius (Ephippiochthonius) poeninus Mahnert, 1979 was recorded for the first time outside of Switzerland. The preferred habitat at the locality Alpe Einödsberg (Germany, Bavaria) differs strongly from previous findings. Our data suggest an association with Nardus grasslands (Geo montani-Nardetum), whereas earlier records originated from leaf litter, moss and mouldy trunks. Furthermore, the new records between 1540 m and 1973 m above sea level are the first from the subalpine region of the Alps (hitherto C. poeninus was known from 550 m to 1450 m). In the study region, extensive grazing seems to have a positive effect on the abundance of the species, while it is missing from intensively grazed pastures.
Spiders were collected at the massif 'Panský diel' near the city of Banská Bystrica (Central Slovakia). We recorded 252 spider species for the territory and one new species for Slovakia. Although the summit reaches an altitude of 1.100 m a.s.l., more or less thermophilous species apparently prevail here, especially at lower moderate sites. On the other hand, only several typical oreophilous species were documented. Many recorded species are scarce or even very rare. This indicates the very high value of this territory from both a genetic and an environmental perspective.
Pandava laminata : eine weitere nach Deutschland importierte Spinnenart (Araneae: Titanoecidae)
(2008)
Pandava laminata (Thorell, 1878) was recorded for the first time from Germany at the Cologne Zoo. The species was most likely introduced with plants or cargo from Southeast Asia. Characters important for identification at species, genus and family level are listed and partly illustrated.
In September 2005, one male specimen of the wolf spider genus Alopecosa was discovered and photographed in heathland near Haltern, North Rhine-Westphalia, Germany. It was identified as A. barbipes (Sundevall, 1833), as it showed the species- and sex-specific tibial hair-brush absent in the sibling species A. accentuata. Three years later, two other specimens of A. barbipes were collected in the same area. These findings indicate that the species is more widespread than originally thought. Some details concerning the distribution of A. accentuata and A. barbipes and the problem of synonymy are discussed.
Wer sich mit der Spinnenfauna der Kaukasusregion oder speziell des Landes Georgien beschäftigt, der wird unausweichlich auf den Namen einer georgischen Arachnologin treffen, die während der vergangenen 70 Jahre die arachnologische Forschung ihres Heimatlandes maßgeblich bestimmt hat. Als erste aus der Kaukasusregion stammende Arachnologin führte Tamara Severyanovna Mkheidze (Abb. 1) in Kooperation mit zumeist russischen Kollegen seit den 1930er Jahren die vergleichsweise junge Tradition kaukasischer Arachnologie fort, die mit einer ersten Bearbeitung im Kaukasus gesammelter Spinnen durch KOCH (1866) ihren Anfang gefunden hatte.
The rare money spider Walckenaeria simplex Chyzer, 1894 was found in 2007 near the city of Meißen (Germany) on a rock overlooking the river Elbe. This is the northernmost occurrence of the species. W. simplex is distributed from Central to South Eastern Europe. The species is thermophilous and prefers wooded slopes with a southern exposition.
Spider fauna of semi-dry grasslands on a military training base in Northwest Germany (Münster)
(2008)
The spider fauna of semi-dry grasslands on the military training area of Dorbaum near Münster (North Rhine-Westphalia) was investigated. From 2002 to 2003 a total of 11,194 mature spiders from 141 species and 20 families was caught by pitfall trapping and hand sampling. Among them are 18 species listed in the Red Data Book of North Rhine-Westphalia, four species are rare or previously rarely recorded. Most of the spiders are habitat generalists that extend their occurrence into all types of habitats, while the number of species which are stenotopic to sand habitats is noticeably low (n = 13). The spider data were analysed with Principal Component Analysis (PCA). It is possible to distinguish spider communities of neighbouring forested habitats from species groups of open habitats, but there is no uniform spider community which is characteristic for semi-dry grassland.
A list of records of 10 spider species that have not been recorded for Schleswig-Holstein/Germany so far and that were found between the years 2004 and 2007 is given. Additional notes about some other 18 species from the regional red list are made.
The spider species Hypsocephalus dahli (Lessert, 1909) is recorded for the first time in Switzerland from museum material collected in 1974. The information given in the literature and unpublished data on this rare species are summarised including an annotated distribution map. All published pictures of males are compared with the holotype. Figures of the male palp and the vulva of the Swiss specimens are provided.
L. religiosum Simon, 1879 was found at Mayen near Koblenz (Rhineland-Palatinate), Germany. This is the first record for Germany and is about 500 km from the known distribution area of the species in the southwestern Alps. The German population seems to be restricted to the ancient Roman quarry “Mayener Grubenfeld” where it is confined to stone walls and cave systems with balanced microclimatic conditions. Genital morphological structures were found to be very fragile, were easily deformed and therefore apparently variable. Difficulties in using these characters for taxonomy are discussed. Ecology, provenance and conservation status of the newly discovered population are considered.
From the beginning of May 2005 to September 2007 the pseudoscorpion fauna in a hardwood floodplain forest of the Rhine valley near Ingelheim was investigated. Altogether 587 individuals representing two species from two families were captured using pitfall traps, trunk eclectors and by litter sieving. The warm, dry winter 2006/2007 exhibited a strong influence upon the activity of Neobisium carcinoides (Hermann, 1804). This winter event was followed by an extreme drought in April 2007, which affected the activity maximum of the corticolous species Chernes hahnii (C.L. Koch, 1839). In 2005 and 2006 the activity maximum of C. hahnii was observed in July, whereas in 2007 maturity was achieved earlier in May. Furthermore 31 individuals of N. carcinoides were captured in trunk eclectors. This climbing behaviour correlates with the presence of Lepidocyrtus lignorum (Collembola: Entomobryidae) on the trunks.
Keywords: activity, Collembola, drought, false scorpions, Germany, prey capture
In the summers of 2006 and 2007 presumed bites of Cheiracanthium spiders triggered mass hysteria in Austria and some regions of Germany, including northern Saxonia. Here we report the first records of Cheiracanthium mildei L. Koch, 1864 from Saxony and new records of C. punctorium (Villers, 1789) from Saxony and Brandenburg. C. punctorium is probably a native species in southern Germany. It shows a moderate area expansion that could be driven by global warming. Further records in north-western Saxony are to be expected. By contrast, C. mildei has to be regarded an invasive alien species that has rapidly spread into Central Europe from the Mediterranean. Leipzig is the north-easternmost locality in Europe reached so far, a further 230 km away from Nuremberg, the leading edge in 2006. A number of records in different districts of Leipzig suggest that the species is already established in the town. We also report verified bites of both species. The mild to moderate symptoms are in accordance with recent literature reviews.
The spider fauna of open habitats adjacent to arable land was investigated in northern Switzerland. The three habitat types were (1) herbaceous edges of fields (Sa), (2) fallow land sowed with flowers (BB), and (3) grass borders of fields (GS). Four funnel pitfall traps (10 cm diameter) were used to catch spiders in three stripe-types in two geographical regions in two years over 5 weeks in May and June: in total 12 sets of data. Spider species typical for open habitats were dominant, mostly lycosids (6 of the 10 most active species). The results were analysed together with environmental factors using a canonical correspondence analysis (CCA) and spiders were compared with carabid beetles (Coeloptera: Carabidae). Geographical region, though not very distant, had the largest influence on both spiders and carabids. The age and type of the habitats had a stronger influence on spiders than on carabids. In spiders a larger part of the total variance was explained by the analysed factors. Finally we discuss briefly a remarkable spider species. A review of all known records of Phrurolithus nigrinus in Switzerland and Germany, together with adjacent regions in France, is given. Its phenology is indicated, its habitat discussed and the overall distribution within Europe is listed.
Background: A number of the deeper divergences in the placental mammal tree are still inconclusively resolved despite extensive phylogenomic analyses. A recent analysis of 200 kbp of protein coding sequences yielded only limited support for the relationships among Laurasiatheria (cow, dog, bat and shrew), probably because the divergences occurred only within a few million years from each other. It is generally expected that increasing the amount of data and improving the taxon sampling enhance the resolution of narrow divergences. Therefore these and other difficult splits were examined by phylogenomic analysis of the hitherto largest sequence alignment. The increasingly complete genome data of placental mammals also allowed developing a novel and stringent data search method. Results: The rigorous data handling, recursive BLAST, successfully removed the sequences from gene families, including those from well-known families hemoglobin, olfactory, myosin and HOX genes, thus avoiding alignment of possibly paralogous sequences. The current phylogenomic analysis of 3,012 genes (2,844,615 nucleotides) from a total of 22 species yielded statistically significant support for most relationships. While some major clades were confirmed using genomic sequence data, the placement of the treeshrew, bat and the relationship between Boreoeutheria, Xenarthra and Afrotheria remained problematic to resolve despite the size of the alignment. Phylogenomic analysis of divergence times dated the basal placental mammal splits at 95–100 million years ago. Many of the following divergences occurred only a few (2–4) million years later. Relationships with narrow divergence time intervals received unexpectedly limited support even from the phylogenomic analyses. Conclusion: The narrow temporal window within which some placental divergences took place suggests that inconsistencies and limited resolution of the mammalian tree may have their natural explanation in speciation processes such as lineage sorting, introgression from species hybridization or hybrid speciation. These processes obscure phylogenetic analysis, making some parts of the tree difficult to resolve even with genome data.
A highly efficient method for chromosomal integration of cloned DNA into Methanosarcina spp. was developed utilizing the site-specific recombination system from the Streptomyces phage PhiC31. Host strains expressing the PhiC31 integrase gene and carrying an appropriate recombination site can be transformed with non-replicating plasmids carrying the complementary recombination site at efficiencies similar to those obtained with self-replicating vectors. We have also constructed a series of hybrid promoters that combine the highly expressed M. barkeri PmcrB promoter with binding sites for the tetracycline-responsive, bacterial TetR protein. These promoters are tightly regulated by the presence or absence of tetracycline in strains that express the tetRgene. The hybrid promoters can be used in genetic experiments to test gene essentiality by placing a gene of interest under their control. Thus, growth of strains with tetR-regulated essential genes becomes tetracycline-dependent. A series of plasmid vectors that utilize the site-specific recombination system for construction of reporter gene fusions and for tetracycline regulated expression of cloned genes are reported. These vectors were used to test the efficiency of translation at a variety of start codons. Fusions using an ATG start site were the most active, whereas those using GTG and TTG were approximately one half or one fourth as active, respectively. The CTG fusion was 95% less active than the ATG fusion.
Quantitative analysis of snoRNA association with pre-ribosomes and release of snR30 by Rok1 helicase
(2008)
In yeast, three small nucleolar RNAs (snoRNAs) are essential for the processing of pre-ribosomal RNA—U3, U14 and snR30—whereas 72 non-essential snoRNAs direct site-specific modification of pre-rRNA. We applied a quantitative screen for alterations in the pre-ribosome association to all 75 yeast snoRNAs in strains depleted of eight putative helicases implicated in 40S subunit synthesis. For the modification-guide snoRNAs, we found no clear evidence for the involvement of these helicases in the association or dissociation of pre-ribosomes. However, the DEAD box helicase Rok1 was required specifically for the release of snR30. Point mutations in motif I, but not in motif III, of the helicase domain of Rok1 impaired the release of snR30, but this was less marked than in strains depleted of Rok1, and resulted in a dominant-negative growth phenotype. Dissociation of U3 and U14 from pre-ribosomes is also dependent on helicases, suggesting that release of the essential snoRNAs might differ mechanistically from release of the modification-guide snoRNAs. Keywords: ribosome biogenesis; RNA helicase; snoRNA
Poster presentation: Introduction The brain is a highly interconnected network of constantly interacting units. Understanding the collective behavior of these units requires a multi-dimensional approach. The results of such analyses are hard to visualize and interpret. Hence tools capable of dealing with such tasks become imperative. ....
Breaking tolerance to the natural human liver autoantigen cytochrome P450 2D6 by virus infection
(2008)
Autoimmune liver diseases, such as autoimmune hepatitis (AIH) and primary biliary cirrhosis, often have severe consequences for the patient. Because of a lack of appropriate animal models, not much is known about their potential viral etiology. Infection by liver-tropic viruses is one possibility for the breakdown of self-tolerance. Therefore, we infected mice with adenovirus Ad5 expressing human cytochrome P450 2D6 (Ad-2D6). Ad-2D6–infected mice developed persistent autoimmune liver disease, apparent by cellular infiltration, hepatic fibrosis, “fused” liver lobules, and necrosis. Similar to type 2 AIH patients, Ad-2D6–infected mice generated type 1 liver kidney microsomal–like antibodies recognizing the immunodominant epitope WDPAQPPRD of cytochrome P450 2D6 (CYP2D6). Interestingly, Ad-2D6–infected wild-type FVB/N mice displayed exacerbated liver damage when compared with transgenic mice expressing the identical human CYP2D6 protein in the liver, indicating the presence of a stronger immunological tolerance in CYP2D6 mice. We demonstrate for the first time that infection with a virus expressing a natural human autoantigen breaks tolerance, resulting in a chronic form of severe, autoimmune liver damage. Our novel model system should be instrumental for studying mechanisms involved in the initiation, propagation, and precipitation of virus-induced autoimmune liver diseases.
Our understanding of the impact of recombination, mutation, genetic drift and selection on the evolution of a single gene is still limited. Here we investigate the impact of all of these evolutionary forces at the complementary sex determiner (csd) gene which evolves under a balancing mode of selection. Females are heterozygous at the csd gene and males are hemizygous; diploid males are lethal and occur when csd is homozygous. Rare alleles thus have a selective advantage, are seldom lost by the effect of genetic drift and are maintained over extended periods of time when compared to neutral polymorphisms. Here, we report on the analysis of 17, 19 and 15 csd alleles of Apis cerana, Apis dorsata and Apis mellifera honey bees respectively. We observed great heterogeneity of synonymous (pi S) and nonsynonymous (pi N) polymorphisms across the gene, with a consistent peak in exon 6 and 7. We propose that exons 6 and 7 encode the potential specifying domain (csd-PSD) which has accumulated elevated nucleotide polymorphisms over time by balancing selection. We observed no direct evidence that balancing selection favors the accumulation of nonsynonymous changes at csd-PSD (pi N/pi S ratios are all < 1, ranging from 0.6 to 0.95). We observed an excess of shared nonsynonymous changes, which suggests that strong evolutionary constraints are operating at csd-PSD resulting in the independent accumulation of the same nonsynonymous changes in different alleles across species (convergent evolution). Analysis of a csd-PSD genealogy revealed relatively short average coalescence times (~6 million years), low average synonymous nucleotide diversity (pi S < 0.09) and a lack of trans-specific alleles which substantially contrasts with previously analyzed loci under strong balancing selection. We excluded the possibility of a burst of diversification after population bottlenecking and intragenic recombination as explanatory factors, leaving high turn-over rates as the explanation for this observation. By comparing observed allele richness and average coalescence times with a simplified model of csd-coalescence, we found that small long term population sizes (i.e. Ne <104), but not high mutation rates, can explain short maintenance times, implicating a strong impact of genetic drift on the molecular evolution of highly social honey bees.
Background Drought is the major constraint to increase yield in chickpea (Cicer arietinum). Improving drought tolerance is therefore of outmost importance for breeding. However, the complexity of the trait allowed only marginal progress. A solution to the current stagnation is expected from innovative molecular tools such as transcriptome analyses providing insight into stress-related gene activity, which combined with molecular markers and expression (e)QTL mapping, may accelerate knowledge-based breeding. SuperSAGE, an improved version of the serial analysis of gene expression (SAGE) technique, generating genome-wide, high-quality transcription profiles from any eukaryote, has been employed in the present study. The method produces 26 bp long fragments (26 bp tags) from defined positions in cDNAs, providing sufficient sequence information to unambiguously characterize the mRNAs. Further, SuperSAGE tags may be immediately used to produce microarrays and probes for real-time-PCR, thereby overcoming the lack of genomic tools in non-model organisms. Results We applied SuperSAGE to the analysis of gene expression in chickpea roots in response to drought. To this end, we sequenced 80,238 26 bp tags representing 17,493 unique transcripts (UniTags) from drought-stressed and non-stressed control roots. A total of 7,532 (43%) UniTags were more than 2.7-fold differentially expressed, and 880 (5.0%) were regulated more than 8-fold upon stress. Their large size enabled the unambiguous annotation of 3,858 (22%) UniTags to genes or proteins in public data bases and thus to stress-response processes. We designed a microarray carrying 3,000 of these 26 bp tags. The chip data confirmed 79% of the tag-based results, whereas RT-PCR confirmed the SuperSAGE data in all cases. Conclusion This study represents the most comprehensive analysis of the drought-response transcriptome of chickpea available to date. It demonstrates that – inter alias – signal transduction, transcription regulation, osmolyte accumulation, and ROS scavenging undergo strong transcriptional remodelling in chickpea roots already 6 h after drought stress. Certain transcript isoforms characterizing these processes are potential targets for breeding for drought tolerance. We demonstrate that these can be easily accessed by micro-arrays and RT-PCR assays readily produced downstream of SuperSAGE. Our study proves that SuperSAGE owns potential for molecular breeding also in non-model crops.
Wo wächst die Palmyrapalme? : mit Satellitendaten praxistaugliche Verbreitungskarten erstellen
(2008)
Die äthiopische Palmyrapalme (Borassus aethiopum) mit einer Wuchshöhe von bis zu 30 Metern gehört zu den größten afrikanischen Palmenarten. Ihr Erhalt ist für die Menschen in Benin und Burkina Faso von großer Bedeutung, denn sie stellen aus den Blättern der Palme Matten, Körbe und Hüte her. Die melonengroßen, glänzend orangen Früchte sind essbar. Inzwischen geht das Verbreitungsgebiet dieser wichtigen Nutzart stark zurück. ...
Der Ozean gehört zu den am wenigsten erforschten Regionen unseres Planeten, obwohl er für den Wärme- und Energiehaushalt der Erde und die Gemeinschaft ihrer Bewohner eine wichtige Rolle spielt. Der Mensch fischt und badet vor allem in den Flachmeeren. Dort ist auch die Schifffahrt am dichtesten. Doch obwohl die Flachmeere nur etwa 5 Prozent des Ozeanbodens ausmachen, wirken sich Veränderungen empfindlich auf alle Meeresbewohner aus, bis in die dunkle, kalte und nahrungsarme Tiefsee.
Dem Wandel rechtzeitig begegnen : Landesförderung ermöglicht richtungsweisende Klimafolgenforschung
(2008)
In diesem Verzeichnis werden Biotoptypen gemäß §32 Naturschutzgesetzes Abs. 1 in Baden-Würtemberg wiedergegeben. Die Unterteilung erfolgt in Gewässer, Terrestrisch-morphologische Biotoptypen, Gehölzarme terrestrische und semiterrestrische Biotoptypen, Gehölzbestände und Gebüsche, Wälder und Biotoptypen der Siedlungs- und Infrastrukturflächen mit Angaben der jeweiligen Flächen und Naturschutzstatus.
Les végétations arbustives des voisinages des cours d’eau ont été étudiées à partir de 34 relevés phytosociologiques réalisés entre septembre 2001 et décembre 2003, en utilisant la méthode phytosociologique de Braun Blanquet. Deux associations végétales en sont décrites: Feretio-Khayetum senegalensis et Celtido-Diospyroetum mespiliformis. Une alliance nouvelle et un ordre nouveau sont créés pour les regrouper. Il s’agit du Feretio-Khayion senegalensis et du Diospyro-Khayetalia senegalensis. Cet ordre rassemble les groupements vallicoles de la zone de transition soudano sahélienne et est considéré comme vicariante géographique du Pterygotetalia Lebrun et Gilbert 1954. Aussi, le Diospyro-Khayion senegalensis all. nov est consirédéré comme vicariante géographique du Khayo-Pterygotion Schmitz 1950 et du Psychotrio-Tecleion Schmitz 1971. Mots clés: Diospyro-Khayetalia senegalensis, Diospyro-Khayion senegalensis, Parc Régional du W du fleuve Niger
Les résultats de 227 relevés phytosociologiques selon l’approche phytosociologique effectuées au Parc Urbain Bangr-Wéoogo de Braun-Blanquet (1932) montrent que malgré son contexte de forte pression anthropique avec plus d´un million d’habitants aux alentours, cette forêt urbaine conserve encore de nos jours une diversité floristique appréciable avec 327 espèces inventoriées comprenant 117 espèces ligneuses et 210 espèces herbacées. Cette flore qui est répartie dans 11 groupements individualisés grâce aux espèces différentielles, est constituée essentiellement de phanérophytes et de thérophytes. La répartition phytogéographique des espèces montre leur appartenance à plusieurs empires phytogéographiques dominés par les espèces Soudano-Zambeziennes et Pantropicales. La richesse floristique du parc qui contraste avec son environnement, est le résultat d’une politique d’aménagement et de conservation efficace de la biodiversité initiée par l'État et ses partenaires depuis 1936. Mots clés: Flore, conservation, aménagement, spectre biologique, Parc Urbain, Ouagadougou, Burkina Faso, groupements végétaux
L´analyse de dix groupements ligneux et dix espèces dominantes a été faite du nombre de tiges à l’hectare et des classes de diamètre des populations correspondantes. Il ressort que les groupements les plus denses sont ceux à Combretum nigricans Lepr. ex Guill. & Perr., Anogeissus leiocarpus (DC.) Guill. & Perr., Acacia hockii De Wild. et A. dudgeoni Craib. ex Holland, tandis que les moins denses sont ceux à Gardenia ternifolia Schumach. & Thonn., Vitellaria paradoxa C. F. Gaertn. et Piliostigma thonningii (Schumach.) Milne-Redh. La répartition des individus en classes de diamètre a révélé que tous les groupements sont stables, c’est-à-dire capables de se renouveler par la régénération naturelle. Mais la structure des espèces dominantes présente beaucoup d’irrégularités liées à leurs exigences écologiques, aux feux de brousse et aux attaques d’éléphants. Toutefois, la plasticité écologique et la biologie de certaines espèces leur confèrent assez de structures de populations stables. Mots clés: Aires protégées, Burkina Faso, Groupements ligneux, Structure de population
Impact of protected areas and land use on regeneration of Acacia woodland’s in Eastern Burkina Faso
(2008)
Regeneration success, persistence strategies (seedlings vs. coppicing), and population trend of Acacia spp. were tested under two land-use regimes in eastern Burkina Faso: (i) protected areas shielded to livestock grazing pressure, to logging, and using early annual fire as a management system; (ii) areas with high human impact (heavily and extensive livestock grazing, harvesting for wood and for medicinal plants). Generally, a good regeneration rate of Acacia species was observed in protected areas and a poor regeneration rate in areas with high human impact. Nevertheless, some species affiliated to the subgenus Aculeiferum as A. dudgeoni and A. polyacantha showed a good regeneration under both land use regimes. Juvenile plants less than 25 cm height of A. dudgeoni and A. gourmaensis increased by 116 to 50 % in areas with human impact as compared to their populations in protected areas. With SCD slopes varying from –0.40 to -0.70, the protected Acacia woodland displayed a stable population structure due to abundance of recruitment, and coppicing persistence (more common in the subgenus Aculeiferum) favoured by early annual fire. Consequently, the protected areas are favourable for Acacia woodland regeneration. Conversely, SCD slopes are positive or close to zero in areas of anthropogenic regime and showed a declining population, especially more marked with the subgenus Acacia due to permanent seed and seedling removal by livestock grazing. Nevertheless, the number of seedlings of some species was higher in areas under human pressure than in protected areas, especially for the subgenus Aculeiferum, improving the genetic variability and thus the long-term maintenance of the population. Key words: Acacia, early fire, land use, sudano-sahelien zone
La présente étude menée sur la végétation ligneuse du parc national d’Arly a pour objectif de caractériser la diversité et la structure des différents groupements végétaux en relation avec les conditions écologiques. 243 relevés phytosociologiques ont été réalisés. Ces relevés font ressortir 109 espèces ligneuses et 10 groupements par la méthode d’analyse DCA. La diversité des groupements végétaux a été caractérisée par le calcul des indices de diversité. Pour chaque groupement ligneux, 10 relevés ont été choisis de manière aléatoire pour des mesures dendrométriques. Les individus dont le diamètre à 1,3 m du sol est supérieur à 5 cm ont été mesurés. La structure des groupements a été décrite à travers la répartition des individus en classe de diamètre, le calcul de la densité et de la surface terrière. La relation entre la diversité et la structure des groupements a été établie sur la base d’analyse de corrélation. Les groupements ligneux distingués sont répartis suivant le gradient topographique. L’analyse de la structure démographique en classe de diamètre montre que les peuplements des différents groupements végétaux sont stables, ce qui traduit leur adaptation aux facteurs écologiques stationnelles telles que le feu et les conditions de sol. Les forêts claires à Tamarindus indica et Combretum paniculatum et les forêts galeries à Vitex chrysocarpa et Garcinia livingstonei sont les formations les plus denses et les groupements ligneux les plus diversifiés. A l’opposé, les savanes arbustives clairsemées à Euphorbia sudanica et Combretum niorense et celles à Acacia sieberiana sont moins denses et constituent les groupements les plus pauvres en espèces. Ainsi, il existe une relation entre la diversité et la structure des groupements des formations ligneuses. Les conditions édaphiques et topographiques occupées par ces groupements expliquent à la fois leur diversité et leur structure. Mots clés: groupements ligneux, relevés, stabilité, sol
A small-world network has been suggested to be an efficient solution for achieving both modular and global processing-a property highly desirable for brain computations. Here, we investigated functional networks of cortical neurons using correlation analysis to identify functional connectivity. To reconstruct the interaction network, we applied the Ising model based on the principle of maximum entropy. This allowed us to assess the interactions by measuring pairwise correlations and to assess the strength of coupling from the degree of synchrony. Visual responses were recorded in visual cortex of anesthetized cats, simultaneously from up to 24 neurons. First, pairwise correlations captured most of the patterns in the population´s activity and, therefore, provided a reliable basis for the reconstruction of the interaction networks. Second, and most importantly, the resulting networks had small-world properties; the average path lengths were as short as in simulated random networks, but the clustering coefficients were larger. Neurons differed considerably with respect to the number and strength of interactions, suggesting the existence of "hubs" in the network. Notably, there was no evidence for scale-free properties. These results suggest that cortical networks are optimized for the coexistence of local and global computations: feature detection and feature integration or binding.
Background One of the central issues in ecology is the question what allows sympatric occurrence of closely related species in the same general area? The non-biting midges Chironomus riparius and C. piger, interbreeding in the laboratory, have been shown to coexist frequently despite of their close relatedness, similar ecology and high morphological similarity. Methodology/Principal Findings In order to investigate factors shaping niche partitioning of these cryptic sister species, we explored the actual degree of reproductive isolation in the field. Congruent results from nuclear microsatellite and mitochondrial haplotype analyses indicated complete absence of interspecific gene-flow. Autocorrelation analysis showed a non-random spatial distribution of the two species. Though not dispersal limited at the scale of the study area, the sister species occurred less often than expected at the same site, indicating past or present competition. Correlation and multiple regression analyses suggested the repartition of the available habitat along water chemistry gradients (nitrite, conductivity, CaCO3), ultimately governed by differences in summer precipitation regime. Conclusions We show that these morphologically cryptic sister species partition their niches due to a certain degree of ecological distinctness and total reproductive isolation in the field. The coexistence of these species provides a suitable model system for the investigation of factors shaping the distribution of closely related, cryptic species.
Introduction : extent, processes and evolutionary impact of interspecific hybridization in animals
(2008)
Since the time of Charles Darwin, studies of interspecific hybridization have been a major focus for evolutionary biologists. Although this phenomenon has often been viewed as problematic in the fields of ecology, taxonomy and systematics, it has become a primary source of data for studies on speciation and adaptation. Effects from genetic/evolutionary processes, such as recombination and natural selection, usually develop over extended periods of time; however, they are accelerated in cases of hybridization. Interspecific hybrids exhibit novel genomes that are exposed to natural selection, thus providing a key to unravel the ultimate causes of adaptation and speciation. Here we provide firstly a historic perspective of hybridization research, secondly a novel attempt to assess the extent of hybridization among animals and thirdly an overview of the reviews and case studies presented in this theme issue.
Using (13)C spin relaxation NMR in combination with molecular dynamic (MD) simulations, we characterized internal motions within double-stranded DNA on the pico- to nano-second time scale. We found that the C-H vectors in all cytosine ribose moieties within the Dickerson-Drew dodecamer (5´-CGCGAATTCGCG-3´) are subject to high amplitude motions, while the other nucleotides are essentially rigid. MD simulations showed that repuckering is a likely motional model for the cytosine ribose moiety. Repuckering occurs with a time constant of around 100 ps. Knowledge of DNA dynamics will contribute to our understanding of the recognition specificity of DNA-binding proteins such as cytosine methyltransferase.
Targeting signals direct proteins to their extra- or intracellular destination such as the plasma membrane or cellular organelles. Here we investigated the structure and function of exceptionally long signal peptides encompassing at least 40 amino acid residues. We discovered a two-domain organization ("NtraC model") in many long signals from vertebrate precursor proteins. Accordingly, long signal peptides may contain an N-terminal domain (N-domain) and a C-terminal domain (C-domain) with different signal or targeting capabilities, separable by a presumably turn-rich transition area (tra). Individual domain functions were probed by cellular targeting experiments with fusion proteins containing parts of the long signal peptide of human membrane protein shrew-1 and secreted alkaline phosphatase as a reporter protein. As predicted, the N-domain of the fusion protein alone was shown to act as a mitochondrial targeting signal, whereas the C-domain alone functions as an export signal. Selective disruption of the transition area in the signal peptide impairs the export efficiency of the reporter protein. Altogether, the results of cellular targeting studies provide a proof-of-principle for our NtraC model and highlight the particular functional importance of the predicted transition area, which critically affects the rate of protein export. In conclusion, the NtraC approach enables the systematic detection and prediction of cryptic targeting signals present in one coherent sequence, and provides a structurally motivated basis for decoding the functional complexity of long protein targeting signals.
Exported proteases of Helicobacter pylori (H. pylori) are potentially involved in pathogen-associated disorders leading to gastric inflammation and neoplasia. By comprehensive sequence screening of the H. pylori proteome for predicted secreted proteases, we retrieved several candidate genes. We detected caseinolytic activities of several such proteases, which are released independently from the H. pylori type IV secretion system encoded by the cag pathogenicity island (cagPAI). Among these, we found the predicted serine protease HtrA (Hp1019), which was previously identified in the bacterial secretome of H. pylori. Importantly, we further found that the H. pylori genes hp1018 and hp1019 represent a single gene likely coding for an exported protein. Here, we directly verified proteolytic activity of HtrA in vitro and identified the HtrA protease in zymograms by mass spectrometry. Overexpressed and purified HtrA exhibited pronounced proteolytic activity, which is inactivated after mutation of Ser205 to alanine in the predicted active center of HtrA. These data demonstrate that H. pylori secretes HtrA as an active protease, which might represent a novel candidate target for therapeutic intervention strategies.