排序方式: 共有67条查询结果,搜索用时 796 毫秒
31.
VALÉRIE DEFFONTAINE†‡ RONAN LEDEVIN§ MICHAËL C. FONTAINE†¶ JEAN-PIERRE QUÉRɆ SABRINA RENAUD§ ROLAND LIBOIS JOHAN R. MICHAUX† †† 《Molecular ecology》2009,18(11):2489-2502
The Pyrenean region exhibits high levels of endemism suggesting a major contribution to the phylogeography of European species. But, to date, the role of the Pyrenees and surrounding areas as a glacial refugium for temperate species remains poorly explored. In the current study, we investigated the biogeographic role of the Pyrenean region through the analyses of genetic polymorphism and morphology of a typical forest-dwelling small mammal, the bank vole ( Myodes glareolus ). Analyses of the mitochondrial cytochrome b gene and the third upper molar (M3 ) show a complex phylogeographic structure in the Pyrenean region with at least three distinct lineages: the Western European, Spanish and Basque lineages. The Basque lineage in the northwestern (NW) Pyrenees was identified as a new clearly differentiated and geographically localized bank vole lineage in Europe. The average M3 shape of Basque bank voles suggests morphological differentiation but also restricted genetic exchanges with other populations. Our genetic and morphological results as well as palaeo-environmental and fossils records support the hypothesis of a new glacial refugium in Europe situated in the NW Pyrenees. The permissive microclimatic conditions that prevailed for a long time in this region may have allowed the survival of temperate species, including humans. Moreover, local differentiation around the Pyrenees is favoured by the opportunity for populations to track the shift of the vegetation belt in altitude rather than in latitude. The finding of the Basque lineage is in agreement with the high level of endemic taxa reported in the NW Pyrenees. 相似文献
32.
Patterns of size and shape differentiation during the evolutionary radiation of the European Miocene murine rodents 总被引:2,自引:0,他引:2
SABRINA RENAUD JACQUES MICHAUX PIERRE MEIN JEAN-PIERRE AGUILAR JEAN-CHRISTOPHE AUFFRAY 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1999,32(1):61-71
Fourier analysis applied to the outlines of the first upper and lower molars of European Miocene murine rodents was used to quantify the size and shape variations associated with their radiation and to determine the evolutionary relationships among the taxa. The results suggested the occurrence of two lineages involving different evolutionary patterns. Size exhibits a rapid diversification in both lineages, probably because of selective pressures related to increasing competition among species. With regard to shape, one of the lineages is characterized by a conservative morphology, and the other by a tooth evolution oriented toward broader molars, which is interpreted as an adaptive specialization. Size and shape evolution are diversely associated during the radiation, and they may be related to the morphological differentiation of co-existing species and the avoidance of interspecific competition. 相似文献
33.
SAMUEL PIRLOT JULIE VANDERHEYDEN JEAN-PIERRE DESCY PIERRE SERVAIS 《Freshwater Biology》2005,50(7):1219-1232
1. This study focused on heterotrophic microorganisms in the two main basins (north and south) of Lake Tanganyika during dry and wet seasons in 2002. Bacteria (81% cocci) were abundant (2.28–5.30 × 106 cells mL?1). During the dry season, in the south basin, bacterial biomass reached a maximum of 2.27 g C m?2 and phytoplankton biomass was 3.75 g C m?2 (integrated over a water column of 100 m). 2. Protozoan abundance was constituted of 99% of heterotrophic nanoflagellates (HNF). Communities of flagellates and bacteria consisted of very small but numerous cells. Flagellates were often the main planktonic compartment, with a biomass of 3.42–4.43 g C m?2. Flagellate biomass was in the same range and often higher than the total autotrophic biomass (1.60–4.72 g C m?2). 3. Total autotrophic carbon was partly sustained by the endosymbiotic zoochlorellae Strombidium. These ciliates were present only in the euphotic zone and usually contributed most of the biomass of ciliates. 4. Total heterotrophic ciliate biomass ranged between 0.35 and 0.44 g C m?2. In 2002, heterotrophic microorganisms consisting of bacteria, flagellates and ciliates represented a large fraction of plankton. These results support the hypothesis that the microbial food web contributes to the high productivity of Lake Tanganyika. 5. As the sole source of carbon in the pelagic zone of this large lake is phytoplankton production, planktonic heterotrophs ultimately depend on autochthonous organic carbon, most probably dissolved organic carbon (DOC) from algal excretion. 相似文献
34.
JEAN-PIERRE GAUTIER 《Bioacoustics.》2013,22(1):11-21
ABSTRACT A phylogeny of guenons was drawn up from the analysis of the acoustic structure of their cohesion, contact and alarm calls, as well as of the loud calls of the adult males. The plesiomorphic or apomorphic state of every acoustic parameter retained was inferred from comparisons with calls given by papionines and/or colobines. A cladistic method was used for analysing a matrix of species by character. The proposed phylogeny separates guenons into two groups: the one includes all forest- living arboreal forms, the other most of the terrestrially-adapted species. The latter, together with C. nigroviridis, which lie close to the origin from which all guenons diverged, share a relatively primitive position, while the arboreal species are the most derived living representatives of the taxon. Quite reliable interspecific affinities are found among arboreal forms, while there are some inconsistencies for the more primitive species. Such results suggest that cercopithecines would have undergone a radiation from more or less open habitats into forests, the evolution proceeding from large-bodied, partly-terrestrial forms to smaller arboreal ones. 相似文献
35.
GUOQING DING GABRIELLE MAUME MARIE-LOUISE MILAT CLAUDE HUMBERT JEAN-PIERRE BLEIN BERNARD F. MAUME 《Cell biology international》1996,20(8):523-530
The proliferation of GM16 and 4CDTras-transformed newborn rat adrenocortical (RTAC) cells and Y1 mouse adrenal tumor cells was inhibited by beticolins, the fungal toxins extracted fromCercospora beticola, at submicromolar concentrations in a dose-dependent manner. Inhibitory concentrations for half the maximum inhibition were 150, 75 and 25 nm for beticolin-1 and 230, 150 and 50 nm for beticolin-2 in GM16, 4CDT and Y1 cells respectively. Beticolins strongly inhibited the production of 11β-hydroxysteroids on the second and third days of treatment in a dose-dependent manner between 0.1 and 1 μm . Beticolins were shown by confocal microscopy to be localized in cytoplasmic organelles about 30–40 min after treatment. This finding favors a direct action of beticolins on mitochondrial steroid 11β-hydroxylase albeit another less direct mechanism involving a cytoplasmic signaling pathway cannot be excluded. 相似文献
36.
Melanoides tuberculata was introduced to several types of aquatichabitat occurring in the marshy forest zone, Guadeloupe, asa competitor of the snail host, Biomphalaria glabrata, of Schistosomamansoni. Colonization by the competitor was successful in allhabitats, but the impact on the snail host was variable accordingto the site. Evolution of global prevalences, intensities andabundances of Schistosoma mansoni in the reservoir host, Rattusrattus, did not show any significant changes during the eightyears following the introduction of the competitor. The analysisof size distribution of M. tuberculata in a release plot showedthat maximum reproduction took place during the rainy seasonbetween June and November. The thiarid snail needed 4.5 monthsto reach a size of 10 mm, 14 months to reach 15 mm, and morethan 30 months to reach 20 mm. Calculated life expectancieswere 0.74 year at the first year of age, 0.9 year at the secondyear, and 0.5 year at the third year. (Received 21 September 1992; accepted 5 January 1993) 相似文献
37.
UNCOUPLING OF OOCYTE-FOLLICLE CELLS TRIGGERS REINITIATION OF MEIOSIS IN AMPHIBIAN OOCYTES 总被引:1,自引:1,他引:0
JEAN-PIERRE VILAIN MARC MOREAU PIERRE GUERRIER 《Development, growth & differentiation》1980,22(4):687-691
Reinitiation of meiosis has been triggered in vitro in oocytes of the anouran Xenopus laevis and the urodeles Pleurodeles waltlii and Ambystoma mexicanum by enzymatic, mechanical or manual defolliculation, without addition of hormone. By measuring changes in the membrane resistance and time constants, we also demonstrate the existence of an electrical polarized coupling between the oocyte and its follicle and show that progesterone breaks it definitively within the first two hours. These results are discussed in relation to mammalian maturation. 相似文献
38.
39.
40.