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1.
Willem‐Jan Emsens Lennart Suselbeek Ben T. Hirsch Roland Kays Annemarie J. S. Winkelhagen Patrick A. Jansen 《Biotropica》2013,45(1):88-93
Animals that rely on refuges for safety can theoretically increase their foraging area without simultaneously increasing predation risk and travel costs by using more refuges. The key prediction of this theory, a negative correlation between food abundance, home range size and the number of refuges used, has never been empirically tested. We determined how home range size and refuge use by the Central American agouti (Dasyprocta punctata) varied across a gradient of abundance of the agoutis' principal food source: seeds and fruits of the palm Astrocaryum standleyanum. We used both manual and automated radio telemetry to measure space use of 11 agoutis during 2 mo of the Astrocaryum fruiting season, and of another set of 10 agoutis during 6 mo in which the animals largely relied on cached Astrocaryum seeds. We found that agoutis living in areas of lower food density had larger home ranges, and that all individuals used multiple refuges. The number of refuges, however, was not correlated with home range size. Consequently, agoutis that had larger home ranges roamed farther from their refuges. These results suggest that agoutis increase their home range size in response to food scarcity at the cost of their safety. 相似文献
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Carol X. Garzon‐Lopez Liliana Ballesteros‐Mejia Alejandro Ordoñez Stephanie A. Bohlman Han Olff Patrick A. Jansen 《Ecology letters》2015,18(8):752-760
The coexistence of numerous tree species in tropical forests is commonly explained by negative dependence of recruitment on the conspecific seed and tree density due to specialist natural enemies that attack seeds and seedlings (‘Janzen–Connell’ effects). Less known is whether guilds of shared seed predators can induce a negative dependence of recruitment on the density of different species of the same plant functional group. We studied 54 plots in tropical forest on Barro Colorado Island, Panama, with contrasting mature tree densities of three coexisting large seeded tree species with shared seed predators. Levels of seed predation were far better explained by incorporating seed densities of all three focal species than by conspecific seed density alone. Both positive and negative density dependencies were observed for different species combinations. Thus, indirect interactions via shared seed predators can either promote or reduce the coexistence of different plant functional groups in tropical forest. 相似文献
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Suzanne M. Stas Else M. Langbroek Robert Bitariho Douglas Sheil Pieter A. Zuidema 《African Journal of Ecology》2017,55(1):30-36
Balancing forest conservation with resource extraction by local people is challenging. In the mountain forests of Bwindi Impenetrable National Park in Uganda, this was addressed by permitting regulated access to certain forest products in specific areas by authorized local people. However, it remained unclear whether harvest levels were biologically sustainable. Here, we used matrix population models and long‐term data to examine the impacts of bark harvesting on population dynamics of two important medicinal plants, Rytigynia kigeziensis and Ocotea usambarensis, in Bwindi. Only 4% of R. kigeziensis and 3% of O. usambarensis stems (>1.3 m height) showed signs of bark harvest, mostly mild harvesting. We found that the harvested populations of both species appeared stable or will moderately grow in the long run. Modelled population growth rates were mostly determined by survival probabilities. Similarity between the stable stage distributions predicted by the model and observed population structures suggests that our estimated vital rates (growth, recruitment and survival rates) are a reasonable representation of actual values in these populations. Thus, recent harvest levels of R. kigeziensis and O. usambarensis appear sustainable. Nonetheless, monitoring of harvested and unharvested populations by tagging, marking and remeasuring individuals should continue for both species. 相似文献
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While disease‐induced extinction is generally considered rare, a number of recently emerging infectious diseases with load‐dependent pathology have led to extinction in wildlife populations. Transmission is a critical factor affecting disease‐induced extinction, but the relative importance of transmission compared to load‐dependent host resistance and tolerance is currently unknown. Using a combination of models and experiments on an amphibian species suffering extirpations from the fungal pathogen Batrachochytrium dendrobatidis (Bd), we show that while transmission from an environmental Bd reservoir increased the ability of Bd to invade an amphibian population and the extinction risk of that population, Bd‐induced extinction dynamics were far more sensitive to host resistance and tolerance than to Bd transmission. We demonstrate that this is a general result for load‐dependent pathogens, where non‐linear resistance and tolerance functions can interact such that small changes in these functions lead to drastic changes in extinction dynamics. 相似文献
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Jean‐Marie Kahindo Robert Nasi Jean‐Pierre Mate Clément Rigal 《African Journal of Ecology》2015,53(3):331-338
Rattans, one of the major non‐timber forest products used by the population in and around Kisangani (Democratic Republic of Congo), are a significant source of income and the basis of a very active informal sector focused towards supplying the city with raw canes. We present the effects of harvest and light availability on the demography of two common rattan species in the Yoko forest reserve, near Kisangani: Eremospatha haullevilleana De Wild. and Laccosperma secundiflorum (P. Beauv.) Küntze. We studied clump demography for a year, under variable light condition and harvesting regimes (control, partial harvest and complete harvest of adult stems). We show a positive effect of full and partial light availability on the dynamic of individuals for both species but with variable treatment responses. We also demonstrate that a partial harvest of two‐thirds of adults cane is beneficial or nondetrimental to the production of new shoots under partial or full‐light conditions. These results suggest opportunities for multiple‐use management that integrate timber and rattan harvesting in forest around Kisangani. 相似文献
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Joachim P. Töpper Eric Meineri Siri L. Olsen Knut Rydgren Olav Skarpaas Vigdis Vandvik 《Global Change Biology》2018,24(10):4657-4666
In climate change ecology, simplistic research approaches may yield unrealistically simplistic answers to often more complicated problems. In particular, the complexity of vegetation responses to global climate change begs a better understanding of the impacts of concomitant changes in several climatic drivers, how these impacts vary across different climatic contexts, and of the demographic processes underlying population changes. Using a replicated, factorial, whole‐community transplant experiment, we investigated regional variation in demographic responses of plant populations to increased temperature and/or precipitation. Across four perennial forb species and 12 sites, we found strong responses to both temperature and precipitation change. Changes in population growth rates were mainly due to changes in survival and clonality. In three of the four study species, the combined increase in temperature and precipitation reflected nonadditive, antagonistic interactions of the single climatic changes for population growth rate and survival, while the interactions were additive and synergistic for clonality. This disparity affects the persistence of genotypes, but also suggests that the mechanisms behind the responses of the vital rates differ. In addition, survival effects varied systematically with climatic context, with wetter and warmer + wetter transplants showing less positive or more negative responses at warmer sites. The detailed demographic approach yields important mechanistic insights into how concomitant changes in temperature and precipitation affect plants, which makes our results generalizable beyond the four study species. Our comprehensive study design illustrates the power of replicated field experiments in disentangling the complex relationships and patterns that govern climate change impacts across real‐world species and landscapes. 相似文献
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Polysaccharides (PF) from marine macroalgae, Caulerpa scalpelliformis were extracted and tested for its potential immunostimulatory and disease resistance properties in fish. Five groups of Nile tilapia (n = 6), Oreochromis niloticus (Linnaeus, 1758) were intraperitoneally administered with the different doses of PF (2, 20 or 200 mg/kg body weight) or with yeast‐derived commercial immunostimulant, Macrogard? (20 mg/kg body weight), to compare the effectiveness. An untreated control group was also maintained. A total of fifteen fibre reinforced plastic tanks (150 L, ambient temperature and light conditions) were used, with triplicate tanks for each group. Only four fish per tank (totally 12 fish from a group) were taken at random and assayed. PF enhanced all the tested non‐specific serum immune responses namely lysozyme, myeloperoxidase, antiprotease, and bactericidal activities. There was an upregulation of the genes encoding IL‐1β, lysozyme and TNF‐α in the spleen of PF injected fish as compared to the control group. In order to study the overall functional immunity, disease resistance test was conducted. Another five groups of fish (n = 10) were treated by intraperitoneal injection with different doses of PF or Macrogard? or untreated as mentioned earlier in triplicates (30 fish per group in three tanks, totally 150 fish in 15 tanks). Seven days post treatment, fish were challenged by intraperitoneal administration of live virulent Aeromonas hydrophila. PF treated fish were protected with significant reduction in the mortality and the consequent increased relative percent survival (RPS) of 92 in the least (2 mg/kg) and middle dose (20 mg/kg) groups. The disease resistance experiment was repeated again but this time, fish were challenged 21 days post treatment that resulted in RPS of 50 for the middle dose. The results clearly show that the intraperitoneal administration of the polysaccharide fraction had a stimulating effect on the non‐specific immune responses, immune gene expression and disease resistance. 相似文献
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Natural enemies attracted to plants may provide those plants with protection against herbivores but may also protect neighbouring plants, that is through associational resistance. Ant attendance may be an important mechanism for the occurrence of such effects because ants can reduce the damage caused by a wide variety of herbivorous insects. Ants have been shown, in a previous field experiment, to decrease the damage caused by the pine weevil, Hylobius abietis (L.) (Coleoptera: Curculionidae), a pest species that causes high seedling mortality in forest regeneration areas. In this study, we specifically tested whether seedlings planted close to ant‐attended seedlings experience associational resistance. We did this under laboratory conditions using the ant species Lasius niger (L.) (Hymenoptera: Formicidae). The feeding damage by pine weevils was significantly reduced on seedlings attended by ants. The neighbouring seedlings, however, did not experience associational resistance. Nevertheless, some associational effects were observed as the number of weevils recorded on both ant‐attended and neighbouring seedlings was significantly lower compared with ant‐excluded seedlings. 相似文献
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Studies on the ecological impacts of non‐timber forest products (NTFP) harvest reveal that plants are often more resilient to fruit and seed harvest than to bark and root harvest. Several studies indicate that sustainable fruit harvesting limits can be set very high (>80% fruit harvesting intensity). For species with clonal and sexual reproduction, understanding how fruit harvest affects clonal reproduction can shed light on the genetic risks and sustainability of NTFP harvest. We studied 18 populations of a gallery forest tree, Pentadesma butyracea (Clusiaceae), to test the impact of fruits harvest, climate and habitat size (gallery forest width) on the frequency of sexual or clonal recruitment in Benin, West Africa. We sampled populations in two ecological regions (Sudanian and Sudano‐Guinean) and in each region, we selected sites with low, moderate and high fruit harvesting intensities. These populations were selected in gallery forests with varying width to sample the natural variation in P. butyracea habitat size. Heavily harvested populations produced significantly less seedlings but had the highest density and proportion of clonal offspring. Our study suggests that for plant species with dual reproductive strategy (via seeds and clonal), fruit harvesting and associated disturbances that come with it can lead to an increase in the proportion of clonal offspring. This raises the issue that excessive fruit harvest by increasing the proportion of clonal offspring to the detriment of seed originated offspring may lead to a reduction in genetic diversity with consequence on harvested species capability to withstand environmental stochasticity. 相似文献
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Ronny Vlz Ju‐Young Park Soonok Kim Sook‐Young Park William Harris Hyunjung Chung Yong‐Hwan Lee 《The Plant journal : for cell and molecular biology》2020,103(1):412-429
The fungal genus Cochliobolus describes necrotrophic pathogens that give rise to significant losses on rice, wheat, and maize. Revealing plant mechanisms of non‐host resistance (NHR) against Cochliobolus will help to uncover strategies that can be exploited in engineered cereals. Therefore, we developed a heterogeneous pathosystem and studied the ability of Cochliobolus to infect dicotyledons. We report here that C. miyabeanus and C. heterostrophus infect Arabidopsis accessions and produce functional conidia, thereby demonstrating the ability to accept Brassica spp. as host plants. Some ecotypes exhibited a high susceptibility, whereas others hindered the necrotrophic disease progression of the Cochliobolus strains. Natural variation in NHR among the tested Arabidopsis accessions can advance the identification of genetic loci that prime the plant’s defence repertoire. We found that applied phytotoxin‐containing conidial fluid extracts of C. miyabeanus caused necrotic lesions on rice leaves but provoked only minor irritations on Arabidopsis. This result implies that C. miyabeanus phytotoxins are insufficiently adapted to promote dicot colonization, which corresponds to a retarded infection progression. Previous studies on rice demonstrated that ethylene (ET) promotes C. miyabeanus infection, whereas salicylic acid (SA) and jasmonic acid (JA) exert a minor function. However, in Arabidopsis, we revealed that the genetic disruption of the ET and JA signalling pathways compromises basal resistance against Cochliobolus, whereas SA biosynthesis mutants showed a reduced susceptibility. Our results refer to the synergistic action of ET/JA and indicate distinct defence systems between Arabidopsis and rice to confine Cochliobolus propagation. Moreover, this heterogeneous pathosystem may help to reveal mechanisms of NHR and associated defensive genes against Cochliobolus infection. 相似文献
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Mit mutations that disrupt function of the mitochondrial electron transport chain can, inexplicably, prolong Caenorhabditis elegans lifespan. In this study we use a metabolomics approach to identify an ensemble of mitochondrial‐derived α‐ketoacids and α‐hydroxyacids that are produced by long‐lived Mit mutants but not by other long‐lived mutants or by short‐lived mitochondrial mutants. We show that accumulation of these compounds is dependent on concerted inhibition of three α‐ketoacid dehydrogenases that share dihydrolipoamide dehydrogenase (DLD) as a common subunit, a protein previously linked in humans with increased risk of Alzheimer's disease. When the expression of DLD in wild‐type animals was reduced using RNA interference we observed an unprecedented effect on lifespan – as RNAi dosage was increased lifespan was significantly shortened, but, at higher doses, it was significantly lengthened, suggesting that DLD plays a unique role in modulating length of life. Our findings provide novel insight into the origin of the Mit phenotype. 相似文献
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W. L. Yee 《Journal of Applied Entomology》2015,139(4):289-301
Bright yellow sticky rectangles made of paper boards were previously identified as the most effective traps for capturing western cherry fruit fly, Rhagoletis indifferens Curran (Dipt., Tephritidae). However, no data on the effectiveness of commercial sticky yellow plastic traps against R. indifferens have been reported. In tests conducted in sweet cherry trees [Prunus avium (L.) L.] in Washington state (USA) using ammonium carbonate as the chemical lure, commercial plastic ‘Yellow Sticky Strips’ made of translucent high‐impact polystyrene captured ~two or three times more flies than commercial sticky yellow‐folded Pherocon® AM and Alpha Scents boards. Yellow Sticky Strips also minimized captures of non‐target flies and bees per surface area compared with Pherocon®AM and/or Alpha Scents boards. Trap size and adhesive type were not factors for greater catches of R. indifferens. However, more flies were caught on the shade‐facing side of Yellow Sticky Strips, which was brightly illuminated, than on the shade‐facing side of boards, which was darker, suggesting differential light passage was a factor. The Yellow Sticky Strips could be very useful for monitoring R. indifferens in detection programmes and based on the results of this study can replace yellow boards. They are also useful because they are relatively unattractive to non‐target insects. 相似文献
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Shafagh A Waters Sean P McAteer Grzegorz Kudla Ignatius Pang Nandan P Deshpande Timothy G Amos Kai Wen Leong Marc R Wilkins Richard Strugnell David L Gally David Tollervey Jai J Tree 《The EMBO journal》2017,36(3):374-387
RNA sequencing studies have identified hundreds of non‐coding RNAs in bacteria, including regulatory small RNA (sRNA). However, our understanding of sRNA function has lagged behind their identification due to a lack of tools for the high‐throughput analysis of RNA–RNA interactions in bacteria. Here we demonstrate that in vivo sRNA–mRNA duplexes can be recovered using UV‐crosslinking, ligation and sequencing of hybrids (CLASH). Many sRNAs recruit the endoribonuclease, RNase E, to facilitate processing of mRNAs. We were able to recover base‐paired sRNA–mRNA duplexes in association with RNase E, allowing proximity‐dependent ligation and sequencing of cognate sRNA–mRNA pairs as chimeric reads. We verified that this approach captures bona fide sRNA–mRNA interactions. Clustering analyses identified novel sRNA seed regions and sets of potentially co‐regulated target mRNAs. We identified multiple mRNA targets for the pathotype‐specific sRNA Esr41, which was shown to regulate colicin sensitivity and iron transport in E. coli. Numerous sRNA interactions were also identified with non‐coding RNAs, including sRNAs and tRNAs, demonstrating the high complexity of the sRNA interactome. 相似文献
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Xiang Yu Qing Zuo Shiyun Huang Lizhou Sun 《Journal of cellular and molecular medicine》2018,22(2):1214-1223
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E. Petrussa F. Boscutti A. Vianello V. Casolo 《Plant biology (Stuttgart, Germany)》2018,20(2):346-356
- Knowledge on the metabolism of polysaccharide reserves in wild species is still scarce. In natural sites we collected tubers of Arum italicum Mill. and A. maculatum L. – two geophytes with different apparent phenological timing, ecology and chorology – during five stages of the annual cycle in order to understand patterns of reserve accumulation and degradation.
- Both the entire tuber and its proximal and distal to shoot portion were utilised. Pools of non‐structural carbohydrates (glucose, sucrose and starch), glucose‐6‐phosphate and ATP were analysed as important markers of carbohydrate metabolism.
- In both species, starch and glucose content of the whole tuber significantly increased from sprouting to the maturation/senescence stages, whereas sucrose showed an opposite trend; ATP and glucose‐6‐phosphate were almost stable and dropped only at the end of the annual cycle. Considering the two different portions of the tuber, both ATP and glucose‐6‐phosphate concentrations were higher in proximity to the shoot in all seasonal stages, except the flowering stage.
- Our findings suggest that seasonal carbon partitioning in the underground organ is driven by phenology and occurs independently of seasonal climate conditions. Moreover, our results show that starch degradation, sustained by elevated ATP and glucose‐6‐phosphate pools, starts in the peripheral, proximal‐to‐shoot portion of the tuber, consuming starch accumulated in the previous season, as a ‘Last In–First Out’ mechanism of carbohydrate storage.