88 research outputs found
Functional and taxonomic typology of pine communities in Algiers and Oran areas (Algeria)
Les mesures classiques de la biodiversitĂ©, telles que la richesse ou la diversitĂ© spĂ©cifique, ne tiennent pas intrinsĂšquement compte des caractĂ©ristiques Ă©cologiques et Ă©volutives des espĂšces et ne renseignent quâincomplĂštement sur les causes et consĂ©quences des changements de biodiversitĂ©. Des formations Ă Pin dâAlep Pinus halepensis Mill. sont Ă©tudiĂ©es dans deux secteurs phytogĂ©ographiques : lâAlgĂ©rois Ă bioclimat subhumide et humide, et lâOranais Ă bioclimat semi-aride. Lâobjectif de cette Ă©tude est dâanalyser la diversitĂ© floristique des diverses formations Ă Pin dâAlep et de proposer une typologie selon deux approches, lâune fondĂ©e sur lâanalyse taxinomique de la flore et lâautre sur lâanalyse des traits fonctionnels des plantes de ces deux secteurs. Des Analyses Factorielles des Correspondances ont Ă©tĂ© rĂ©alisĂ©es dans ces deux cas et leurs rĂ©sultats comparĂ©s et discutĂ©s. Lâanalyse taxinomique fait ressortir des descripteurs Ă©cologiques contrastĂ©s (altitude, substrat, etc.) et explique la rĂ©partition de la vĂ©gĂ©tation par rapport aux facteurs Ă©cologiques, sans toutefois faire ressortir de diffĂ©rence significative entre les deux secteurs. Lâanalyse fonctionnelle a permis dâidentifier les traits dominants dans chacun des deux secteurs, permettant ainsi de dĂ©finir des groupes fonctionnels de plantes propres Ă chacun. La comparaison des rĂ©sultats obtenus entre les deux secteurs montre que les formations Ă©tudiĂ©es sâorganisent selon un gradient phytogĂ©ographique, un gradient altitudinal et un gradient de perturbations. Les facteurs Ă©cologiques classiques mis en Ă©vidence par l'approche taxonomique nâont pas pu expliquer Ă eux seuls la dynamique des peuplements, mais l'apport des traits fonctionnels est venu complĂ©ter et prĂ©ciser l'histoire de la mise en place de la vĂ©gĂ©tation de ces deux secteurs.Standard measurements of biodiversity, such as those based on species diversity and abundance, do not take into account the ecological and evolutionary characteristics of species per se, and provide us with an incomplete understanding of the causes and consequences of changes in biodiversity. Communities of Aleppo pines Pinus halepensis Mill. are under study in two Algerian phytogeographical areas: Algiersâ subhumid and humid bioclimate, and Oranâs semi-arid bioclimate. The purpose of this study is to analyse the floristic diversity of various communities of Aleppo pines, and to provide a typology based on twin approaches: a taxonomic analysis of the flora, and an analysis of the plantsâ functional traits in these two areas. Correspondence factor analysis (CFA) has been conducted in both cases, and the results have been compared and discussed. The taxonomic analysis brings out contrasting ecological descriptors (altitude, substrate, etc.) and explains the plantsâ distribution in relation to their environmental factors, but reveals no significant difference between the two areas under consideration. The functional analysis allowed for the identification of the main functional traits in each of the areas under study, and helped us define several functional groups in each case. A comparison of the results in both sectors shows that the organization of the Aleppo pine communities under consideration is principled upon phytogeographical, altitudinal, and disturbance gradients. Standard ecological factors evidenced by the taxonomic approach cannot single-handedly explain the dynamics of the communities; however, their functional traits have clarified and supplemented the floraâs history in these two areas
LâĂ©tat de changement de la lande Ă Erica scoparia L. sous lâeffet du pĂąturage et de la colonisation par le chĂȘne
Our aim was to ascertain whether changes in plant species richness and other vegetation
features occur in heathland dominated by Erica scoparia L. (besom heath) through the impact of cattle
grazing and oak colonization. Our study took place in the Brenne Regional Natural Park (center of France)
where this ericaceous species, locally called âbrandeâ, is now considered of patrimonial interest and protected
at regional and European level. We selected 10 sites in a private property, covering a wide range of
ecological conditions (shallow and deep soils, grazed and non-grazed besom heath, pure and oak-colonized
besom heath). Vegetation (percent occupancy of plant species) was sampled in May-June 2006 (105 samples,
1m2 each) and the impact of shrub and tree vegetation on plant biodiversity was assessed by correspondence
analysis (CA) and total and partial Mantel tests (Monte-Carlo procedure). An environmental gradient
of decreasing light incidence from grazed heath to old heath to oak-wood was depicted, along which a
number of ecological, morphological and physiological plant traits (growth habits, Ellenberg values, Grime
strategies, Tolerance Index of the plant community) were observed to vary. Species richness decreases when
ericaceous or, although to a lesser extent, oak cover increases and it increases under low to moderate cattle
grazing. Consequences for the sustainable management of âbrandeâ are discussedL'Ă©tat de changement de la lande Ă Erica scoparia L. sous l'effet du pĂąturage et de la colonisation par le chĂȘne. - Le but de notre Ă©tude est de mettre en Ă©vidence les modifications de la richesse spĂ©cifique et d'autres caractĂšres
de la vĂ©gĂ©tation qui surviennent sous l'influence du pĂąturage et de la colonisation par le chĂȘne dans les landes dominĂ©es par Erica scoparia L. (brande). L'Ă©tude a Ă©tĂ© menĂ©e dans le Parc Naturel RĂ©gional de la Brenne (France, RĂ©gion Centre) oĂč cette ĂricacĂ©e est aujourd'hui considĂ©rĂ©e comme
patrimoniale et protĂ©gĂ©e au niveau rĂ©gional et europĂ©en. Dix sites ont Ă©tĂ© choisis au sein d'une propriĂ©tĂ© privĂ©e, couvrant un large Ă©ventail de conditions Ă©cologiques (sols superficiels et profonds, brande pĂąturĂ©e et non pĂąturĂ©e, pure et envahie par le chĂȘne). La vĂ©gĂ©tation (pourcentage
d'occupation de l'espace par les différentes espÚces végétales) a été échantillonnée en mai et juin 2006 (105 relevés de 1 m ) et l'impact de la végétation arbustive et arborée sur la biodiversité végétale a été mis en évidence à l'aide de l'analyse des correspondances (AFC) et de tests de
Mantel totaux et partiels (mĂ©thode de Monte-Carlo). Un gradient dĂ©croissant d'incidence de la lumiĂšre a Ă©tĂ© mis en Ă©vidence depuis la brande pĂąturĂ©e jusqu'Ă la brande ĂągĂ©e puis la chĂȘnaie, en rapport avec la variation de nombreux traits Ă©cologiques, morphologiques et physiologiques (types
physionomiques, indices d'Ellenberg, stratĂ©gies de Grime, indice de tolĂ©rance de la communautĂ©). La richesse spĂ©cifique dĂ©croĂźt Ă mesure de l'extension des ĂricacĂ©es ou, dans une moindre mesure, de celle du chĂȘne et s'accroĂźt sous pĂąturage faible Ă modĂ©rĂ©. Les consĂ©quences pour la gestion
durable de la brande sont discutées
Is there an interest to determine the gaitâs profile of MCI subjects to predict the risk of Alzheimer disease?
Can the Mangombe forest plantation contribute to restore and conserve biodiversity?
This research, conducted in the tropical rainforest, is focused on restoration of tree diversity through natural regeneration mechanism in the 49 year-old Mangombe forest plantation. 12 plots were surveyed, 6 with large transects and the 6 others under regrowth. In each plot, two subplots with 400 mÂČ each were demarcated for the inventory of all stems with diameter greater than 2.5 cm. A total of 2239 stems comprising 107 species distributed in 93 genera and 42 families were identified over 9600 mÂČ. There was a slight difference between species richness of plots with large transect (79 species, 72 genera and 35 families) and regrowth plots (85 species, 76 genera and 38 families) while the basal area in the plots with large transects (10.76 mÂČ/ha) was significantly greater than that of regrowth (8.65 mÂČ/ha). Species with high important value index have an affinity with forest undergrowth such as: Tabernaemontana pachysiphon, T. crassa, Mallotus oppositifolius and Heinsia crinita. The undergrowth is diversified with different life feature and a high number of small size trees indicating a vigorous regeneration. This can be favoured by: microclimate undergrowth, canopy gaps, abundance of litter fall that brings humus to the soil, type and age of plots, planted species and the complexity of spatial and vertical structure of the stand.© 2016 International Formulae Group. All rights reserved.Keywords: MangombĂ© â Cameroon, Natural regeneration, dense humid forest, tree plantation, biodiversit
Phytosociological characterization of the vegetation of Gouraya National Park (BĂ©jaĂŻa, Algeria)
Gouraya National Park covers a calcaro-dolomitic littoral solid mass and its silicicolous prolongation
towards the west. It belongs to the regional hotspot of âKabylies-Numidia-Kroumiriaâ but its vegetation
was just partially explored. We try here a first synthesis under the phytosociological point of view. On
the basis of 144 species and 56 floristic ârelevĂ©sâ submitted to factorial correspondence analysis and ascending
hierarchical classification, the phytosociological study of Gouraya National Park highlighted seven vegetation
groups attached to four phytosociological classes : the Quercetea ilicis BraunâBlanquet, 1947 and
subordinated syntaxa, the Querco-Fagetea BraunâBlanquet & Vlieg, 1937 and subordinated syntaxa, and
the Crithmo-limonietea BraunâBlanquet, 1947 and Asplenietea rupestris (H.M) BraunâBlanquet, 1934. We
can note also the presence of species characteristic of the Rosmarinetea officinalis BraunâBlanquet, 1947
em. Rivas Martinez, Diaz, Prieto, Loidi & Penas, 1991 and of Stellarietea mediae R. TX. Lohmeyer & Preising
1950. Within these groups, those assigned to Bupleuro-Euphorbietum dendroidis GĂ©hu et al., 1992 can
be divided in two subgroups, the typical sub-association and a new sub-association named here bupleuretosum
plantaginei, characterized by the presence of rupicolous endemism. This study showed the peculiarity
of the vegetation of this local biodiversity hotspot (important area for plants) and will be followed by a more
in-depth study of the rupicolous littoral and sub-littoral vegetation of the areaLe parc national de Gouraya recouvre un massif littoral calcaro-dolomitique et son prolongement silicicole vers l'ouest. Il appartient au point-chaud régional de « Kabylies-Numidie-Kroumirie » mais sa végétation n'a été que
partiellement explorée. Nous tentons ici une premiÚre synthÚse sous l'angle phytosociologique. Sur la base de 56 relevés floristiques et 144 espÚces soumis à l'analyse factorielle des correspondances et à la classification hiérarchique ascendante, l'étude phytosociologique du parc national
de Gouraya a mis en Ă©vidence sept groupements vĂ©gĂ©taux se rattachant Ă quatre classes phytosociologiques: les Quercetea ilicis BraunâBlanquet, 1947 et syntaxons subordonnĂ©s, les Quer-co-Fagetea BraunâBlanquet et Vlieg, 1937 et syntaxons subordonnĂ©s, les Crithmo-limonietea BraunâBlanquet,
1947 et les Asplenietea rupestris (H.M) BraunâBlanquet, 1934. On note aussi la prĂ©sence d'espĂšces caractĂ©ristiques des Rosmarinetea officinalis BraunâBlanquet, 1947 em. Rivas Martinez, Diaz, Prieto, Loidi & Penas, 1991 et des Stellarietea mediae R. TX. Lohmeyer & Preising 1950. Parmi
ces groupements, celui attribué au BupleuroEuphorbietum dendroidis Géhu et al., 1992 peut se découper en deux sous-groupements, la sous-association type et une sous-association nouvelle nommée ici bupleuretosum plantaginei, caractérisée par la présence d'endémisme rupicole. Cette étude a
montré la particularité de la végétation de ce point-chaud local de biodioversité (zone importante pour les plantes) et sera suivie d'une étude plus complÚte sur la végétation rupicole littorale et sublittorale de la région
Look but do not touch: the occurrence of venomous species across Lepidoptera
peer reviewedLepidoptera can cause several health issues in humans and domestic animals due to their setae, which are defensive adaptations that protect them from predators. The diversity of venomous Lepidoptera has been explored in several reviews starting from the first comprehensive attempt in 1984 by Kawamoto and Kumada (KK) who compiled a list of 228 species based on previous reviews; however, KK did not cite the original publications for listed species. In this review we validated and updated the KK table. The updated list of venomous Lepidoptera includes 5 superfamilies, 14 families, 208 genera, and 576 species, representing a two-fold increase for genera and 2.9-fold for species with respect to KK. The total number of species in the genera including at least one venomous species, which we argue is likely closer to the true number of venomous species, is 7 times higher (3,620). GBIF (Global Biodiversity Information Facility) occurrences for venomous species are 1â4 orders of magnitude higher than those of confamilial non-venomous species. The presence of venomous structures is independent of the relatedness of the clades or geographic region; venom is produced by many species of Zygaenoidea, Lasiocampoidea and Bombycoidea but only by some specialized groups in Papilionoidea and Noctuoidea. There are likely to be multiple evolutionary origins of venom within Lepidoptera, but the exact number is difficult to estimate. The knowledge gap between medical and natural history fields needs to be addressed with novel approaches to study ecology and toxicology. This review offers health practitioners a tool to better understand the origin of the reactions observed and to improve the identification of the causal agents
VARIATIONS DEPUIS 10000 ANS DE LA REPARTITION ET DE LA PRODUCTIVITE DES FORETS D'ALTITUDE DANS LES ALPES ET LE JURA ET SIMULATION DES CHANGEMENTS FUTURS
Ce travail repose sur les charbons de bois enfouis dans les sols et les autres macrorestes ont Ă©tĂ© datĂ©s par 14C et identifiĂ©s botaniquement, et pour un site particulier (lac Cristol), sur les analyses de pollens, d'insectes, de macro-restes vĂ©gĂ©taux, charbons de bois et tronc d'arbres ont Ă©tĂ© combinĂ©s en une « approche multi-proxy » afin de mieux comprendre les variations de la forĂȘt de montagne en rĂ©ponse aux changements climatiques globaux et Ă l'activitĂ© anthropique. Les variations de la limite de la forĂȘt sont de plus de 500 m durant l'HolocĂšne. La pĂ©riode la plus chaude semble avoir Ă©tĂ© 9000-8000 ans cal B.P. (annĂ©es calendaires avant le prĂ©sent). Les hauts niveaux lacustres du dĂ©but et de la fin de l'HolocĂšne sont de natures en fait assez diffĂ©rentes. Au dĂ©but de l'HolocĂšne ils sont principalement dus Ă une Ă©vapotranspiration plus faible, et Ă la fin de l'HolocĂšne Ă des prĂ©cipitations plus Ă©levĂ©es. L'ensemble de ces informations a permis de tester un modĂšle de vĂ©gĂ©tation (Biome3) par une utilisation en mode inverse et Ă essayer de prĂ©dire l'Ă©volution de la vĂ©gĂ©tation. Un doublement de CO2 permet Ă la vĂ©gĂ©tation d'Ă©voluer vers des conditions plus tempĂ©rĂ©es. Une « forĂȘt mixte tempĂ©rĂ©e », pourra devenir une forĂȘt dĂ©cidue tempĂ©rĂ©e grĂące Ă des hivers nettement plus doux et Ă une meilleure efficacitĂ© dans l'utilisation de l'eau en Ă©tĂ©. Ces sites d'altitude ont connu une telle vĂ©gĂ©tation entre 9000 et 8000 ans cal B.P
Sterol biosensor reveals LAM-family Ltc1-dependent sterol flow to endosomes upon Arp2/3 inhibition.
Sterols are crucial components of biological membranes, which are synthetized in the ER and accumulate in the plasma membrane (PM). Here, by applying a genetically encoded sterol biosensor (D4H), we visualize a sterol flow between PM and endosomes in the fission yeast Schizosaccharomyces pombe. Using time-lapse and correlative light-electron microscopy, we found that inhibition of Arp2/3-dependent F-actin assembly promotes the reversible relocalization of D4H from the PM to internal sterol-rich compartments (STRIC) labeled by synaptobrevin Syb1. Retrograde sterol internalization to STRIC is independent of endocytosis or an intact Golgi, but depends on Ltc1, a LAM/StARkin-family protein localized to ER-PM contact sites. The PM in ltc1Î cells over-accumulates sterols and upon Arp2/3 inhibition forms extended ER-interacting invaginations, indicating that sterol transfer contributes to PM size homeostasis. Anterograde sterol movement from STRIC is independent of canonical vesicular trafficking but requires Arp2/3, suggesting a novel role for this complex. Thus, transfer routes orthogonal to vesicular trafficking govern the flow of sterols in the cell
The novel proteins Rng8 and Rng9 regulate the myosin-V Myo51 during fission yeast cytokinesis.
The myosin-V family of molecular motors is known to be under sophisticated regulation, but our knowledge of the roles and regulation of myosin-Vs in cytokinesis is limited. Here, we report that the myosin-V Myo51 affects contractile ring assembly and stability during fission yeast cytokinesis, and is regulated by two novel coiled-coil proteins, Rng8 and Rng9. Both rng8Î and rng9Î cells display similar defects as myo51Î in cytokinesis. Rng8 and Rng9 are required for Myo51's localizations to cytoplasmic puncta, actin cables, and the contractile ring. Myo51 puncta contain multiple Myo51 molecules and walk continuously on actin filaments in rng8(+) cells, whereas Myo51 forms speckles containing only one dimer and does not move efficiently on actin tracks in rng8Î. Consistently, Myo51 transports artificial cargos efficiently in vivo, and this activity is regulated by Rng8. Purified Rng8 and Rng9 form stable higher-order complexes. Collectively, we propose that Rng8 and Rng9 form oligomers and cluster multiple Myo51 dimers to regulate Myo51 localization and functions
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