共查询到20条相似文献，搜索用时 15 毫秒
1.
Amadou Dawé Marius Mbiantcha Yannick Fongang William Yosseu Nana Fawai Yakai Gilbert Ateufack Muhammad Ali Shaiq Iqbal Lubna Mehreen Lateef Bonaventure Tchaleu Ngadjui 《化学与生物多样性》2017,14(2)
Piptadenin ( 1 ), a new triterpene along with piptadenamide ( 10 ), a new ceramide, have been isolated from the AcOEt‐soluble fraction of the MeOH extract of the stem bark of Piptadeniastrum africanum along with nine known compounds, 1‐O‐[(3β,22β)‐3,22‐dihydroxy‐28‐oxoolean‐12‐en‐28‐yl]‐β‐d ‐glucopyranose ( 2 ), 22β‐hydroxyoleanic acid ( 3 ), oleanic acid ( 4 ), lupeol ( 5 ), betulinic acid ( 6 ), 5α‐stigmasta‐7,22‐dien‐3β‐ol ( 7 ), 5α‐stigmasta‐7,22‐dien‐3‐one ( 8 ), (3β)‐stigmast‐5‐en‐3‐yl β‐d ‐glucopyranoside ( 9 ) and 2,3‐dihydroxypropyl hexacosanoate ( 11 ). Except for compound 11 , all the isolated compounds are reported for the first time from this plant. The structures of the isolated compounds were elucidated by spectroscopic data including 1D and 2D NMR. The pure compounds 1 – 11 were subjected to the pharmacological screening and compounds 2 , 5 – 7 and 9 exhibited potent urease inhibitory activity with IC50 value of 25.8, 28.9, 30.1, 31.8 and 32.7 μm , respectively, whereas compound 1 showed moderate activity (IC50 = 98.7 μm ). The potent urease inhibitory activity supplemented the previous literature reports and medicinal uses of this plant. 相似文献
2.
Jeroen van der Kooij Georg H. Engelhard David A. Righton 《Journal of Biogeography》2016,43(11):2285-2298
3.
Kenneth Dumack Julia Pundt Michael Bonkowski 《The Journal of eukaryotic microbiology》2020,67(2):245-251
Thecofilosea is a class in Cercozoa (Rhizaria) comprising mainly freshwater‐inhabiting algivores. Recently, numerous isolates of thecofilosean amoebae have been cultured and were characterized by an integrated morphological and molecular approach. As attempts to establish a culture of Lecythium mutabilis repeatedly failed, it was not yet investigated by molecular means. We isolated single cells of L. mutabilis directly from their habitat and successfully sequenced the V4 region of their SSU rDNA. Phylogenetic analyses showed that L. mutabilis is not directly related to the genus Lecythium and instead branches within the Fiscullidae (Tectofilosida, Thecofilosea). Accordingly, we transfer the species L. mutabilis to a novel genus Omnivora gen. nov. 相似文献
4.
Maria Byrne Melanie A. Ho Lucas Koleits Casandra Price Catherine K. King Patti Virtue Bronte Tilbrook Miles Lamare 《Global Change Biology》2013,19(7):2264-2275
Stenothermal polar benthic marine invertebrates are highly sensitive to environmental perturbations but little is known about potential synergistic effects of concurrent ocean warming and acidification on development of their embryos and larvae. We examined the effects of these stressors on development to the calcifying larval stage in the Antarctic sea urchin Sterechinus neumayeri in embryos reared in present and future (2100+) ocean conditions from fertilization. Embryos were reared in 2 temperature (ambient: ?1.0 °C, + 2 °C : 1.0 °C) and 3 pH (ambient: pH 8.0, ?0.2–0.4 pH units: 7.8,7.6) levels. Principle coordinates analysis on five larval metrics showed a significant effect of temperature and pH on the pattern of growth. Within each temperature, larvae were separated by pH treatment, a pattern primarily influenced by larval arm and body length. Growth was accelerated by temperature with a 20–28% increase in postoral (PO) length at +2 °C across all pH levels. Growth was strongly depressed by reduced pH with a 8–19% decrease in PO length at pH 7.6–7.8 at both temperatures. The boost in growth caused by warming resulted in larvae that were larger than would be observed if acidification was examined in the absence of warming. However, there was no significant interaction between these stressors. The increase in left‐right asymmetry and altered body allometry indicated that decreased pH disrupted developmental patterning and acted as a teratogen (agent causing developmental malformation). Decreased developmental success with just a 2 °C warming indicates that development in S. neumayeri is particularly sensitive to increased temperature. Increased temperature also altered larval allometry. Altered body shape impairs swimming and feeding in echinoplutei. In the absence of adaptation, it appears that the larval phase may be a bottleneck for survivorship of S. neumayeri in a changing ocean in a location where poleward migration to escape inhospitable conditions is not possible. 相似文献
5.
M. Tim Tinker Brian B. Hatfield Michael D. Harris Jack A. Ames 《Marine Mammal Science》2016,32(1):309-326
Although southern sea otters (Enhydra lutris nereis) are not considered prey for white sharks (Carcharodon carcharias), sharks do nonetheless bite sea otters. We analyzed spatial and temporal trends in shark bites on sea otters in California, assessing the frequency of shark bite wounds in 1,870 carcasses collected since 1985. The proportion of stranded sea otters having shark bites has increased sharply since 2003, and white shark bites now account for >50% of recovered carcasses. The trend was most pronounced in the southern part of the range, from Estero Bay to Point Conception, where shark bite frequency has increased eightfold. Seasonal trends were also evident: most shark‐bitten carcasses are recovered in late summer and fall; however, the period of elevated shark bite frequency has lengthened. The causes of these trends are unclear, but possible contributing factors include increased white shark abundance and/or changes in white shark behavior and distribution. In particular, the spatiotemporal patterns of shark‐bitten sea otters match increases in pinniped populations, and the increased availability of marine mammal prey for white sharks may have led to more sharks spending more time in nearshore waters utilized by both sea otters and pinnipeds. 相似文献
6.
Gerardo Campos‐Rivero Lorenzo F. Snchez‐Teyer Erika A. De la Cruz‐Arguijo Maria S. Ramírez‐Gonzlez Claudia P. Larralde‐Corona Jos A. Narvez‐Zapata 《Journal of Phytopathology》2019,167(5):283-294
Thirty different fungal strains were isolated from A. tequilana leaves showing disease symptoms such as wilt and curled leaves, black, red and chlorotic spots. Ten genera were identified and confirmed by using the LSU D1/D2 rDNA and ITS1‐5.8S‐ITS2 regions, mainly of the Ascomycota phylum, where the Lasiodiploidia and Neoscytalidium genera were the more (46.6%) abundant. The other genera identified were Cladosporium, Cytospora, Epicoccum, Flavodon, Lasiodiplodia, Myrmaecium, Neoscytalidium, Penicillium, Peniophora, Purpureocillium, Trametes and Fusarium. Five strains of Lasiodiplodia and one of Fusarium were selected based on their representativeness and pathogenic potential on Agaves. Pathogenic potential was analysed by both, an infection assay, evidenced as necrosis, and by pectinolytic activity. Specifically, necrosis infection assay was conducted by puncture (wounded) infection and by direct mycelium contact. In general, Lasiodiplodia strains exhibited different pathogenic profiles according to their necrosis percentages, regardless of the infection method used. Fusarium strain analysed also showed a high necrosis infection (> 99%). Pectinolytic activity used as an indirect measurement of pathogenesis presented a high Fusarium extract activity (peaking at 23.9 U). Lasiodiplodia strains exhibited up 6 times more enzymatic activity (peaking at 143.5) than Fusarium strain analysed. In addition, Agave leaf extracts used totally or partially as carbon source during fungal induction culture may induce different pathogenic activities in these strains. In general, the two pathogenicity assays implemented evidenced differences in the pathogenicity profile of these analysed strains. 相似文献
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8.
Jessica M. Shaw Tim A. Reid Maurice Schutgens Andrew R. Jenkins Peter G. Ryan 《Ibis》2018,160(2):431-446
Quantifying avian collisions with power lines at large spatial scales is difficult, but such mortality is of serious conservation concern for many bird species worldwide. To investigate effects on the Endangered Ludwig's Bustard Neotis ludwigii and two other bustard species, mortality surveys were conducted quarterly along high‐voltage transmission lines at five sites (total length 252 km) across the Karoo for 2 years and one low‐voltage distribution line site (95 km) for 1 year. Thirty bird species were found, with Ludwig's Bustards constituting 69% and other bustards a further 18% of carcasses (n = 679 birds). Significant explanatory variables of Ludwig's Bustard collisions were season (collisions more likely in winter), rainfall (less likely in drier areas) and year on transmission lines (highlighting variability between years). Season and proximity to roads were significant variables on distribution lines, with collisions more likely during winter and away from roads. Ludwig's Bustard collision rates (corrected for survey biases) were higher on transmission (1.12; 95% confidence interval (CI) 0.40–2.58 bustards/km/year) than on distribution lines (0.86; 95% CI 0.30–1.96), but these smaller lines are four times as extensive in South Africa and so probably kill more birds. Despite being much less abundant, Kori Bustards Ardeotis kori were the second most commonly recovered species, with collision rates of 0.10 (95% CI 0.05–0.19) on transmission lines in the Nama Karoo alone. Collision rates are highly variable but suggest mortality suffered by these two species is worryingly high. This adds to growing concern about the impacts of power lines on bustards globally, so given ongoing expansion to the power grid, collision mitigation measures should be implemented at all new power lines. 相似文献
9.
Blake D. Ramsby Malcolm S. Hill Daniel J. Thornhill Sieuwkje F. Steenhuizen Michelle Achlatis Allison M. Lewis Todd C. LaJeunesse 《Journal of phycology》2017,53(5):951-960
Dinoflagellates in the genus Symbiodinium associate with a broad array of metazoan and protistian hosts. Symbiodinium‐based symbioses involving bioeroding sponge hosts have received less attention than those involving popular scleractinian hosts. Certain species of common Cliona harbor high densities of an ecologically restricted group of Symbiodinium, referred to as Clade G. Clade G Symbiodinium are also known to form stable and functionally important associations with Foraminifera and black corals (Antipatharia) Analyses of genetic evidence indicate that Clade G likely comprises several distinct species. Here, we use nucleotide sequence data in combination with ecological and geographic attributes to formally describe Symbiodinium endoclionum sp. nov. obtained from the Pacific boring sponge Cliona orientalis and Symbiodinium spongiolum sp. nov. from the congeneric western Atlantic sponge Cliona varians. These species appear to be part of an adaptive radiation comprising lineages of Clade G specialized to the metazoan phyla Porifera and Cnidaria, which began prior to the separation of the Pacific and Atlantic Oceans. 相似文献
10.
- Many streams today have modified channels, substratum composition, flows and temperature regimes. Understanding how these potential stressors affect key processes governing populations is crucial towards counteracting species decline and loss. For aquatic organisms with complex life cycles that include a terrestrial adult stage, successful reproduction involving a transition from the terrestrial to aquatic environment for oviposition can be an important constraint.
- Our main goal was to test for the effects of local stream degradation on egg mass densities of macroinvertebrates with different requirements for oviposition habitat. We experimentally manipulated oviposition substrate availability in two Swiss gravel‐bed rivers by adding bricks to stream beds of channelised, restored and near natural reaches differing in their depth profile and availability of large rocks. We followed oviposition on bricks and natural rocks between May and October 2008 and quantified egg mass densities of two aquatic insects with a terrestrial stage (Baetis spp. and Hydropsyche spp.) and an entirely aquatic leech Erpobdella octoculata. Individual and interactive effects of mean water depth fluctuations, depth variability, frequency of large rocks and temperature on egg mass densities were evaluated using a model selection approach.
- Response to our manipulation in terms of relative use of bricks for oviposition was strongest in the two insect taxa, whose egg mass densities responded to the presence of large substrata in study reaches. We also found evidence for a weak water level effect on egg mass densities of Baetis, a mayfly that uses protruding rocks for oviposition, in contrast to Hydropsyche, which apparently is capable of diving. While no clear response to our manipulation was found in Erpobdella octoculata, its overall cocoon densities were influenced by the variability of depth profile and increased in reaches with lower streambed heterogeneity.
- Our results suggest that stream degradation has high potential to constrain reproduction of many species, in particular those with complex life cycles such as aquatic insects. Investigation in modified riverscapes of the specific effects of different constraints to recruitment processes is a prerequisite for successful management and conservation.
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Marina Furlan Giubbina Alexandre Camargo Martensen Milton Cezar Ribeiro 《Austral ecology》2018,43(5):527-533
Habitat fragmentation results in landscape configuration, which affects the species that inhabit it. As a consequence, natural habitat is replaced by different anthropogenic plantation types (e.g. pasture, agriculture, forestry plantations and urban areas). Anthropogenic plantations are important for biodiversity maintenance because some species or functional groups can use it as a complementary habitat. However, depending on plantation permeability, it can act as a barrier to the movement of organisms between habitat patches, such as forest fragments, reducing functional connectivity for many species. Anthropogenic plantations are becoming the most common land use and cover type in the Anthropocene and biodiversity conservation in fragmented landscapes requires information on how different plantation types affect the capacity of the species to move through the landscape. In this study, we evaluated the influence of the type and structure of plantations on the movement of two forest‐dependent understory bird species – plain antvireo (Dysithamnus mentalis) and flavescent warbler (Myiothlyps flaveola) – within a highly fragmented landscape of Atlantic Forest hotspot. Knowing that forestry plantation is assumed to be more permeable to dependent forest bird species than open ones, we selected six study areas containing a forest fragment and surrounding plantation: three with sugarcane plantation and three with Eucalyptus sp. plantation. We used playback calls to stimulate the birds to leave forest fragments and traverse the plantations. Control trials were also carried out inside the forest fragments to compare the distances crossed. We observed that individuals moved longer distances inside forest than between plantation types, which demonstrate that plantations do constrict the movements of both species. The two plantation types equally impeded the movements of the species, suggesting the opposite of the general assumption that forestry plantations are more permeable. Our results indicate that, for generalist species, plantation type does not matter, but its presence negatively impacts movement of these bird species. We highlight that plantations have negative influences on the movements of common bird species, and discuss why this is important when setting conservation priorities. 相似文献
13.
Sebastian C.A. Ferse 《Restoration Ecology》2010,18(4):399-407
Worldwide, coral reefs are degrading due to increasing anthropogenic pressures. Yet, management of reefs still falls short of effectively addressing these threats, and active restoration methods are increasingly being called for. Coral transplantation is frequently advocated as a possible means of coral reef rehabilitation. Fragments produced in coral nurseries or farms have been proposed as a potential source for transplantation, and culture media (inexpensive but non‐durable materials such as wood or bamboo) may serve as transplantation substrate if placed directly in the reef. However, the performance of coral transplants attached to such substrates has not been examined yet. Here, the long‐term survival of transplants attached to bamboo substrates is reported. A total of 6,164 fragments of 4 coral species (Acroporids and Pocilloporids) were monitored for up to 20 months at three sites in North Sulawesi/Indonesia. Bamboo failed as a suitable inexpensive substrate in at least two of the three sites examined. Mortality of transplants 2 years after transplantation was high in three of the four species (67–95%) and was partially linked to substrate disintegration. The results show that, in places were currents or waves threaten to dislocate transplants, a higher effort needs to be directed at a strong and durable attachment of transplanted corals. 相似文献
14.
Derek Eamus Nicolas Boulain James Cleverly David D. Breshears 《Ecology and evolution》2013,3(8):2711-2729
Drought‐induced tree mortality is occurring across all forested continents and is expected to increase worldwide during the coming century. Regional‐scale forest die‐off influences terrestrial albedo, carbon and water budgets, and land‐surface energy partitioning. Although increased temperatures during drought are widely identified as a critical contributor to exacerbated tree mortality associated with “global‐change‐type drought”, corresponding changes in vapor pressure deficit (D) have rarely been considered explicitly and have not been disaggregated from that of temperature per se. Here, we apply a detailed mechanistic soil–plant–atmosphere model to examine the impacts of drought, increased air temperature (+2°C or +5°C), and increased vapor pressure deficit (D; +1 kPa or +2.5 kPa), singly and in combination, on net primary productivity (NPP) and transpiration and forest responses, especially soil moisture content, leaf water potential, and stomatal conductance. We show that increased D exerts a larger detrimental effect on transpiration and NPP, than increased temperature alone, with or without the imposition of a 3‐month drought. Combined with drought, the effect of increased D on NPP was substantially larger than that of drought plus increased temperature. Thus, the number of days when NPP was zero across the 2‐year simulation was 13 or 14 days in the control and increased temperature scenarios, but increased to approximately 200 days when D was increased. Drought alone increased the number of days of zero NPP to 88, but drought plus increased temperature did not increase the number of days. In contrast, drought and increased D resulted in the number of days when NPP = 0 increasing to 235 (+1 kPa) or 304 days (+2.5 kPa). We conclude that correct identification of the causes of global change‐type mortality events requires explicit consideration of the influence of D as well as its interaction with drought and temperature. 相似文献
15.
Emma J. Steel Joseph B. Fontaine Katinka X. Ruthrof Treena I. Burgess Giles E. St. J. Hardy 《Austral ecology》2019,44(8):1438-1450
Worldwide, extreme climatic events such as drought and heatwaves are associated with forest mortality. However, the precise drivers of tree mortality at individual and stand levels vary considerably, with substantial gaps in knowledge across studies in biomes and continents. In 2010–2011, a drought‐associated heatwave occurred in south‐western Australia and drove sudden and rapid forest canopy collapse. Working in the Northern Jarrah (Eucalyptus marginata) Forest, we quantified the response of key overstory (E. marginata, Corymbia calophylla) and midstory (Banksia grandis, Allocasuarina fraseriana) tree species to the extreme climate event. Using transects spanning a gradient of drought impacts (minimal (50–100 m), transitional (100–150 m) and severe (30–60 m)), tree species mortality in relation to stand characteristics (stand basal area and stem density) and edaphic factors (soil depth) was determined. We show differential mortality between the two overstory species and the two midstory species corresponding to the drought‐associated heatwave. The dominant overstory species, E. marginata, had significantly higher mortality (~19%) than C. calophylla (~7%) in the severe zone. The midstory species, B. grandis, demonstrated substantially higher mortality (~59%) than A. fraseriana (~4%) in the transitional zone. Banksia grandis exhibited a substantial shift in structure in response to the drought‐associated heatwave in relation to tree size, basal area and soil depth. This study illustrates the role of climate extremes in driving ecosystem change and highlights the critical need to identify and quantify the resulting impact to help predict future forest die‐off events and to underpin forest management and conservation. 相似文献
16.
Joseph B. Ahrens Elizabeth Borda Rômulo Barroso Paulo C. Paiva Alexandra M. Campbell Alexander Wolf Maggy M. Nugues Greg W. Rouse Anja Schulze 《Molecular ecology》2013,22(8):2280-2291
Over the last few decades, advances in molecular techniques have led to the detection of strong geographic population structure and cryptic speciation in many benthic marine taxa, even those with long‐lived pelagic larval stages. Polychaete annelids, in particular, generally show a high degree of population divergence, especially in mitochondrial genes. Rarely have molecular studies confirmed the presence of ‘cosmopolitan’ species. The amphinomid polychaete Hermodice carunculata was long considered the sole species within its genus, with a reported distribution throughout the Atlantic and adjacent basins. However, recent studies have indicated morphological differences, primarily in the number of branchial filaments, between the East and West Atlantic populations; these differences were invoked to re‐instate Hermodice nigrolineata, formerly considered a junior synonym of H. carunculata. We utilized sequence data from two mitochondrial (cytochrome c oxidase subunit I, 16S rDNA) markers and one nuclear (internal transcribed spacer) marker to examine the genetic diversity of Hermodice throughout its distribution range in the Atlantic Ocean, including the Mediterranean Sea, the Caribbean Sea, the Gulf of Mexico and the Gulf of Guinea. Our analyses revealed generally low genetic divergences among collecting localities and between the East and West Atlantic, although phylogenetic trees based on mitochondrial data indicate the presence of a private lineage in the Mediterranean Sea. A re‐evaluation of the number of branchial filaments confirmed differences between East and West Atlantic populations; however, the differences were not diagnostic and did not reflect the observed genetic population structure. Rather, we suspect that the number of branchial filaments is a function of oxygen saturation in the environment. Our results do not support the distinction between H. carunculata in the West Atlantic and H. nigrolineata in the East Atlantic. Instead, they re‐affirm the older notion that H. carunculata is a cohesive species with a broad distribution across the Atlantic Ocean. 相似文献
17.
Mistletoes represent the best example of specialization in seed dispersal, with a reduced assemblage of dispersal agents. Specific dispersal requirements mediated by the specificity of seed deposition site have apparently led to the evolution of such close relationships between mistletoes and certain frugivores. Here, we provide evidences for another case of specialization involving epiphytic cacti in the genus Rhipsalis, and small Neotropical passerines Euphonia spp., which also act as the main seed dispersers of mistletoes in the family Viscaceae. With field observations, literature search, and observations on captive birds, we demonstrated that Rhipsalis have specific establishment requirements, and euphonias are the most effective dispersers of Rhipsalis seeds in both quantitative and qualitative aspects, potentially depositing seeds onto branches of host plants. We interpret the similar dispersal systems of Rhipsalis and Viscaceae mistletoes, which involve the same dispersal agents, similar fruit morphologies, and fruit chemistry as convergent adaptive strategies that enable seeds of both groups to reach adequate microsites for establishment in host branches. 相似文献
18.
Kyaw W. Naing Muhammad Anees Xuan H. Nguyen Yong S. Lee Seung W. Jeon Sang J. Kim Myung H. Kim Kil Y. Kim 《Journal of Phytopathology》2014,162(6):367-376
For field application of a bacterial strain used to control Phythophthora capsici, we will need a biologically and economically efficient carrier medium. The known antagonist Paenibacillus ehimensisKWN38 was grown in a grass medium where it showed high antifungal and lytic enzyme activities. To demonstrate the potential of P. ehimensisKWN38 for biocontrol of late blight disease in pepper, pot trials were conducted by treating the 1‐month‐old plants with water (W), a selected grass medium (G3), G plus P. ehimensisKWN38 inoculation (G3P) or synthetic fungicide (F). The shoot dry weight in G3P was higher than that in W and F treatments at 15 days after zoospore infection (DZI). The root dry weight in G3P was also higher than that in W. The root mortality of G3 and W increased over 58 and 80% at 15 DZI, and some plants in those treatments wilted due to the failure of root physiology. The plants in G3P and F survived well because of their better root health conditions. Soil cellulase activity of G3P was consistently higher than that of W and F at earlier observation times (0, 2 and 6 DZI). The root β‐1,3‐glucanase activity of G3P promptly increased to maximum shortly after zoospore infection and reached the maximum value of 51.12 unit g?1 of fresh weight at 2 DZI. All these results indicate that inoculation of P. ehimensisKWN38 to the root zone of potted pepper plants increases plant growth, root and soil enzyme activities and alleviates the root death caused by infection with P. capsici zoospores. 相似文献
19.
Sharmilee Gnanapavan Peggy Ho Wendy Heywood Sam Jackson Donna Grant Khadija Rantell Geoff Keir Kevin Mills Lawrence Steinman Gavin Giovannoni 《Journal of neurochemistry》2013,125(5):766-773
Multiple sclerosis (MS) is a CNS disorder characterized by demyelination and neurodegeneration. Although hallmarks of recovery (remyelination and repair) have been documented in early MS, the regenerative capacity of the adult CNS per se remains uncertain with the wide held belief that it is either limited or non‐existent. The neural cell adhesion molecule (NCAM) is a cell adhesion molecule that has been widely implicated in axonal outgrowth, guidance and fasciculation. Here, we used in vitro and in vivo of MS to investigate the role of NCAM in disease progression. We show that in health NCAM levels decrease over time, but this occurs acutely after demyelination and remains reduced in chronic disease. Our findings suggest that depletion of NCAM is one of the factors associated with or possibly responsible for disease progression in MS. 相似文献
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