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1.
Background
Natural communities are structured by intra-guild competition, predation or parasitism and the abiotic environment. We studied the relative importance of these factors in two host-social parasite ecosystems in three ant communities in Europe (Bavaria) and North America (New York, West Virginia). We tested how these factors affect colony demography, life-history and the spatial pattern of colonies, using a large sample size of more than 1000 colonies. The strength of competition was measured by the distance to the nearest competitor. Distance to the closest social parasite colony was used as a measure of parasitism risk. Nest sites (i.e., sticks or acorns) are limited in these forest ecosystems and we therefore included nest site quality as an abiotic factor in the analysis. In contrast to previous studies based on local densities, we focus here on the positioning and spatial patterns and we use models to compare our predictions to random expectations. 相似文献2.
Background
To understand variation in resistance to parasites within host populations, researchers have examined conditions under which immunity is induced and/or is costly. Both host sex and age have been found to influence immune expression and subsequently are likely factors influencing the costs of resistance. The purpose of this study was to examine immune expression and associated survival costs for two age groups (newly emerged and sexually mature individuals) of the damselfly, Enallagma boreale Selys. Survival was assessed for experimentally challenged and control damselflies, housed initially at 22°C and then subjected to low temperatures (15°C) associated with reduced foraging activity and food deprivation. Experimental conditions emulated natural local variation in bouts of good weather followed by inclement weather (successions of days with hourly mean temperatures around 15°C and/or rainy weather). 相似文献3.
椰心叶甲啮小蜂(Tetrastichus brontispae Ferrière)是一种重要的椰心叶甲蛹寄生蜂。为了探讨繁育椰心叶甲啮小蜂的最佳寄主密度,研究1对椰心叶甲啮小蜂与椰心叶甲1日蛹的不同配比对椰心叶甲啮小蜂寄生与繁殖的影响。结果表明,雌蜂与椰心叶甲1日龄蛹的不同配比对椰心叶甲啮小蜂寄生率、每寄主出蜂量和后代性比有显著影响,当雌蜂与椰心叶甲1日龄蛹配比为1∶1时,椰心叶甲啮小蜂的寄生率和出蜂量最高,其寄生率为100%,每蛹平均出蜂量为27.67头,显著高于其它配比,但雌蜂与椰心叶甲1日龄蛹配比为1∶6时,椰心叶甲啮小蜂后代性比(雌蜂的百分比)最高为88.04%,显著高于其它配比。平均每雌怀卵量、出蜂率、羽化率在椰心叶甲啮小蜂与椰心叶甲蛹的不同配比之间无显著差异。 相似文献
4.
Farahnaz-Sadat Shayganmehr Masoud Alebouyeh Masoumeh Azimirad Mohammad Mehdi Aslani Mohammad Reza Zali 《Iranian Biomedical Journal》2015,19(3):143-148
Background:
Reduced susceptibility of Clostridium difficile to antibiotics is problematic in clinical settings. There is new evidence indicating the cotransfer of toxin-encoding genes and conjugative transposons encoding resistance to antibiotics among different C. difficile strains. To analyze this association, in the current study, we evaluated the frequency of toxigenic C. difficile among the strains with different multidrug-resistant (MDR) profiles in Iran.Methods:
Antimicrobial susceptibility patterns and minimal inhibitory concentrations (MIC) of the isolates were determined against metronidazole, imipenem, ceftazidime, amikacin, and ciprofloxacin by agar dilution method. The association of the resistance profiles and toxigenicity of the strains were studied by PCR targeting tcdA and tcdB genes.Results:
Among 86 characterized strains, the highest and lowest resistance rates were related to ciprofloxacin (97%) and metronidazole (5%), respectively. The frequency of resistance to other antibiotics was as follow: imipenem (48%), ceftazidime (76%), and amikacin (76.5%). Among the resistant strains, double drug resistance and MDR phenotypes were detected in the frequencies of 10.4% and 66.2%, respectively. All of the metronidazole-resistant strains belonged to tcdA +/tcdB + genotype with triple or quintuple drug resistance phenotypes. MIC50 and MIC90 for this antibiotic was equally ≤ 8 μg/ml.Conclusion:
These results proposed the association of tcdA +/tcdB + genotype of C. difficile and the emergence of resistance strains to broad-spectrum antibiotics and metronidazole. Key Words: Multidrug resistance, Clostridium difficile, Metronidazole 相似文献5.
Kristen E Whalen Victoria R Starczak David R Nelson Jared V Goldstone Mark E Hahn 《BMC ecology》2010,10(1):24
Background
Intense consumer pressure strongly affects the structural organization and function of marine ecosystems, while also having a profound effect on the phenotype of both predator and prey. Allelochemicals produced by prey often render their tissues unpalatable or toxic to a majority of potential consumers, yet some marine consumers have evolved resistance to host chemical defenses. A key challenge facing marine ecologists seeking to explain the vast differences in consumer tolerance of dietary allelochemicals is understanding the biochemical and molecular mechanisms underlying diet choice. The ability of marine consumers to tolerate toxin-laden prey may involve the cooperative action of biotransformation enzymes, including the inducible cytochrome P450s (CYPs), which have received little attention in marine invertebrates despite the importance of allelochemicals in their evolution. 相似文献6.
The Race Structure of the Rice Blast Pathogen Across Southern and Northeastern China 总被引：1，自引：0，他引：1
Yaling Zhang Qiongle Zhu Yongxiang Yao Zhenghong Zhao James C. Correll Ling Wang Qinghua Pan 《Rice》2017,10(1):46
Background
Rice blast, caused by the ascomycete Magnaporthe oryzae (Mo), imposes a major constraint on rice productivity. Managing the disease through the deployment of host resistance requires a close understanding of race structure of the pathogen population.Results
The host/pathogen interaction between isolates sampled from four Mo populations collected across the rice-producing regions of China was tested using two established panels of differential cultivars. The clearest picture was obtained from the Chinese cultivar panel, for which the frequency of the various races, the race diversity index, the specific race isolate frequency, and the frequency of the three predominant races gave a consistent result, from which it was concluded that the pathogen population present in the southern production region was more diverse than that in the northeastern region. The four blast resistance genes Pi1, Pik, Pik-m, and Piz all still remain effective in the southern China rice production area, as does Pi1 in the northeastern region. The effectiveness of Pita, Pik-p, Piz, and Pib is restricted to single provinces. The distinctive resistance profile shown by the Chinese differential cultivar set implied the presence of at least five as yet unidentified blast resistance genes.Conclusions
The Chinese differential cultivar set proved to be more informative than the Japanese one for characterizing the race structure of the rice blast pathogen in China. A number of well characterized host resistance genes, in addition to some as yet uncharacterized ones, remain effective across the major rice production regions in China.7.
Background
The persistence of high genetic variability in natural populations garners considerable interest among ecologists and evolutionary biologists. One proposed hypothesis for the maintenance of high levels of genetic diversity relies on frequency-dependent selection imposed by parasites on host populations (Red Queen hypothesis). A complementary hypothesis suggests that a trade-off between fitness costs associated with tolerance to stress factors and fitness costs associated with resistance to parasites is responsible for the maintenance of host genetic diversity.Results
The present study investigated whether host resistance to parasites is traded off with tolerance to environmental stress factors (high/low temperatures, high salinity), by comparing populations of the freshwater snail Melanoides tuberculata with low vs. high clonal diversity. Since polyclonal populations were found to be more parasitized than populations with low clonal diversity, we expected them to be tolerant to environmental stress factors. We found that clonal diversity explained most of the variation in snail survival under high temperature, thereby suggesting that tolerance to high temperatures of clonally diverse populations is higher than that of populations with low clonal diversity.Conclusions
Our results suggest that resistance to parasites may come at a cost of reduced tolerance to certain environmental stress factors.8.
Yang Wang Weihua Jiang Hongmei Liu Ya Zeng Bo Du Lili Zhu Guangcun He Rongzhi Chen 《Rice》2017,10(1):51
Background
The brown planthopper (BPH) has become the most destructive and a serious threat to the rice production in Asia. Breeding the resistant varieties with improved host resistance is the most effective and ecosystem-friendly strategy of BPH biological management. As host resistance was always broken down by the presence of the upgrading BPH biotype, the more resistant varieties with novel resistance genes or pyramiding known identified BPH resistance genes would be needed urgently for higher resistant level and more durability of resistance.Results
Here, we developed near isogenic lines of Bph9 (NIL-Bph9) by backcrossing elite cultivar 93–11 with Pokkali (harboring Bph9) using marker-assisted selection (MAS). Subsequently, we pyramided Bph6 and Bph9 in 93–11 genetic background through MAS. The resulting Bph6 and Bph9 pyramided line LuoYang69 had stronger antixenotic and antibiosis effects on BPH and exhibited significantly enhanced resistance to BPH than near isogenic lines NIL-Bph6 and NIL-Bph9. LuoYang69 derived hybrids, harboring heterozygous Bph6 and Bph9 genes, also conferred high level of resistance to BPH. Furthermore, LuoYang69 did not affect the elite agronomic traits and rice grain quality of 93–11. The current study also developed functional markers for Bph9. Using functional dominant marker, we screened and evaluated worldwide accessions of rice germplasm. Of the 673 varieties tested, 8 cultivars were identified to harbor functional Bph9 gene.Conclusion
The development of Bph6 and Bph9 pyramided line LuoYang69 provides valuable resource to develop hybrid rice with highly and durable BPH resistance. The development of functional markers will promote MAS of Bph9. The identified Bph9 containing cultivars can be used as new sources for BPH resistance breeding programs.9.
Background
Climate change is particularly pronounced in the High Arctic and a better understanding of the repercussions on ecological processes like herbivory, predation and pollination is needed. Arthropods play an important role in the high-arctic ecosystem and this role is determined by their density and activity. However, density and activity may be sensitive to separate components of climate. Earlier emergence due to advanced timing of snowmelt following climate change may expose adult arthropods to unchanged temperatures but higher levels of radiation. The capture rate of arthropods in passive open traps like pitfall trap integrates density and activity and, therefore, serves as a proxy of the magnitude of such arthropod-related ecological processes. We used arthropod pitfall trapping data and weather data from 10 seasons in high-arctic Greenland to identify climatic effects on the activity pattern of nine arthropod taxa. 相似文献10.
Yvonne L Chan Xavier Pochon Marla A Fisher Daniel Wagner Gregory T Concepcion Samuel E Kahng Robert J Toonen Ruth D Gates 《BMC ecology》2009,9(1):21
Background
Mesophotic corals (light-dependent corals in the deepest half of the photic zone at depths of 30 - 150 m) provide a unique opportunity to study the limits of the interactions between corals and endosymbiotic dinoflagellates in the genus Symbiodinium. We sampled Leptoseris spp. in Hawaii via manned submersibles across a depth range of 67 - 100 m. Both the host and Symbiodinium communities were genotyped, using a non-coding region of the mitochondrial ND5 intron (NAD5) and the nuclear ribosomal internal transcribed spacer region 2 (ITS2), respectively. 相似文献11.
杀虫剂对二化螟卵寄生性天敌稻螟赤眼蜂室内安全性评价 总被引：7，自引：0，他引：7
在实验室条件下测定了6类13种杀虫剂对二化螟卵寄生性天敌稻螟赤眼蜂的直接和间接影响。喷雾法处理稻株不同时间后,噻嗪酮、虫酰肼、呋喃虫酰肼、氟铃脲对稻螟赤眼蜂成蜂存活和雌蜂产卵寄生基本没有不利影响,氟虫腈、噻虫嗪、毒死蜱、三唑磷对稻螟赤眼蜂成蜂存活有极明显不利影响,成蜂接触用药处理2 d和7 d稻叶的死亡率分别为100％和800%~98.9%。用氟虫腈、三唑磷处理7 d的稻叶对稻螟赤眼蜂成蜂寄生能力无不利影响,而噻虫嗪处理有显著影响。采用卵卡浸渍法测定药剂对稻螟赤眼蜂成蜂影响的结果表明,吡虫啉、三唑磷、氟虫腈、毒死蜱能显著影响F0代成蜂存活、寄生及F1代成蜂羽化。采用浸渍法处理内含卵期、幼虫期、预蛹期、蛹期稻螟赤眼蜂的寄生卵时,噻嗪酮、虫酰肼、呋喃虫酰肼对成蜂羽化没有不利影响,羽化率达81.4%~91.8%;氟铃脲对蛹、甲维盐对卵和蛹、噻虫嗪对卵也基本没有不利影响,这些药剂对其他虫态有不同程度的影响;甲胺磷、吡虫啉、三唑磷、氟虫腈、毒死蜱、异丙威、敌敌畏等对稻螟赤眼蜂成蜂羽化有极明显不利影响。说明昆虫生长调节剂噻嗪酮、虫酰肼、呋喃虫酰肼对稻螟赤眼蜂没有直接和间接的不利影响,因而使用这些药剂防治水稻害虫时,它们对起自然控制作用的稻螟赤眼蜂是友好的。 相似文献
12.
Josué H. Rakotoniaina Peter M. Kappeler Eva Kaesler Anni M. Hämäläinen Clemens Kirschbaum Cornelia Kraus 《BMC ecology》2017,17(1):30
Background
Glucocorticoid hormones are known to play a key role in mediating a cascade of physiological responses to social and ecological stressors and can therefore influence animals’ behaviour and ultimately fitness. Yet, how glucocorticoid levels are associated with reproductive success or survival in a natural setting has received little empirical attention so far. Here, we examined links between survival and levels of glucocorticoid in a small, short-lived primate, the grey mouse lemur (Microcebus murinus), using for the first time an indicator of long-term stress load (hair cortisol concentration). Using a capture-mark-recapture modelling approach, we assessed the effect of stress on survival in a broad context (semi-annual rates), but also under a specific period of high energetic demands during the reproductive season. We further assessed the power of other commonly used health indicators (body condition and parasitism) in predicting survival outcomes relative to the effect of long-term stress.Results
We found that high levels of hair cortisol were associated with reduced survival probabilities both at the semi-annual scale and over the reproductive season. Additionally, very good body condition (measured as scaled mass index) was related to increased survival at the semi-annual scale, but not during the breeding season. In contrast, variation in parasitism failed to predict survival.Conclusion
Altogether, our results indicate that long-term increased glucocorticoid levels can be related to survival and hence population dynamics, and suggest differential strength of selection acting on glucocorticoids, body condition, and parasite infection.13.
14.
Conservation biological control, which fosters the optimal use of indigenous natural enemies, is a promising way for reducing pesticide reliance in horticultural systems. A two-year field survey was conducted in the main cabbage-producing area in Senegal (Niayes) to assess the potential of indigenous parasitoids to control populations of Plutella xylostella (Lepidoptera, Plutellidae). Results showed an overall low level of parasitism (11.7%) which was independent of host abundance, but was highly variable among fields (0–50%). Parasitism was predominant in the late part of dry season. Insecticide use, mostly relying on broad-spectrum insecticides, had a negative effect on the overall parasitism rate. Observations conducted throughout the cabbage crop cycle showed that parasitism unexpectedly decreased with crop aging (from 41 to 60 days post transplanting), likely due to repeated insecticide applications. Four main parasitoid species including Oomyzus sokolowskii (Kurdjumov) (Eulophidae) (48.8%), Apanteles litae Nixon (Braconidae) (32.5%), Brachymeria sp. (Chalcididae) (11.3%), and Cotesia vestalis Haliday (Braconidae) (7.3%) were identified. Parasitism due to O. sokolowskii was greater during the first part of the dry season whereas parasitism due to A. litae was greater during the second part of the dry season. Parasitism due to Brachymeria sp. was not affected by time of season but was greater in the Centre and North than in the South of Niayes. Parasitism due to C. vestalis was equal in the three zones but was higher in the late part of the dry season. The diversity of parasitoids was constant across zones but was greater during the second part of dry season. A positive relationship between diversity (Shannon diversity index H′) and parasitism rate was observed, suggesting a positive effect of parasitoid diversity on natural pest control. Parasitoids have a promising role to play as biocontrol agents of P. xylostella populations in Senegal, provided significant changes to current insecticide use are made. Better knowledge of their resource requirements including crop and non-crop habitats, and provision of these in and around crops is also needed. 相似文献
15.
Background
Glucosinolate breakdown products are volatile, therefore good candidates for insect fumigants. However, although they are insecticidal, the mode of action of such natural products is not clear. We studied the insecticidal effect of these compounds as fumigants, and monitored the production of carbon dioxide by the insects as a probe to the understanding of their mode of action. 相似文献16.
Background
Parasites that manipulate host behavior can provide prominent examples of extended phenotypes: parasite genomes controlling host behavior. Here we focus on one of the most dramatic examples of behavioral manipulation, the death grip of ants infected by Ophiocordyceps fungi. We studied the interaction between O. unilateralis s.l. and its host ant Camponotus leonardi in a Thai rainforest, where infected ants descend from their canopy nests down to understory vegetation to bite into abaxial leaf veins before dying. Host mortality is concentrated in patches (graveyards) where ants die on sapling leaves ca. 25 cm above the soil surface where conditions for parasite development are optimal. Here we address whether the sequence of ant behaviors leading to the final death grip can also be interpreted as parasite adaptations and describe some of the morphological changes inside the heads of infected workers that mediate the expression of the death grip phenotype.Results
We found that infected ants behave as zombies and display predictable stereotypical behaviors of random rather than directional walking, and of repeated convulsions that make them fall down and thus precludes returning to the canopy. Transitions from erratic wandering to death grips on a leaf vein were abrupt and synchronized around solar noon. We show that the mandibles of ants penetrate deeply into vein tissue and that this is accompanied by extensive atrophy of the mandibular muscles. This lock-jaw means the ant will remain attached to the leaf after death. We further present histological data to show that a high density of single celled stages of the parasite within the head capsule of dying ants are likely to be responsible for this muscular atrophy.Conclusions
Extended phenotypes in ants induced by fungal infections are a complex example of behavioral manipulation requiring coordinated changes of host behavior and morphology. Future work should address the genetic basis of such extended phenotypes. 相似文献17.
Background
Differences among species and among years in reproductive seasonality (the tendency for clusters of events to fall at approximately the same point in each year) and synchrony (amount of clustering of events within a year) have been intensively studied in bats, but are difficult to assess. Here, we use randomization methods with circular statistics to test for synchrony and seasonality of reproduction in three species of nectarivorous megachiropteran bats on Negros Island in the central Philippines. 相似文献18.
Ehsan Borzoui Bahram Naseri Mozhgan Mohammadzadeh-Bidarani 《Journal of insect science (Online)》2016,16(1)
Food characteristics strongly regulate digestive enzymatic activity of insects through direct influences on their midgut mechanisms. Insect performance is better on diets that contain nutrients in proportions that fit its digestive enzymes. Little is known about the influences of rearing history on parasitism success of Habrobracon hebetor Say. This research focused on the effect of nutrient regulation on survival, development, and parasitism of H. hebetor. Life history and digestive enzyme activity of fourth-stage larvae of H. hebetor were studied when reared on Ephestia kuehniella Zeller. This parasitoid was then introduced to Helicoverpa armigera (Hübner), and above-mentioned parameters were also studied in the first and fourth generations after transfer. In term of parasitism success, H. hebetor preferred E. kuehniella over He. armigera. When the first and fourth generations of He. armigera-reared H. hebetor were compared, the rearing history affected the life history and enzymatic activity of the parasitoid. A better performance of H. hebetor was achieved after it was reared on He. armigera for the four generations. Because, digestive α-amylase and general protease of the parasitoid were matched with the new host, it used reserve energy for a better performance. Thus, a better performance of H. hebetor could be obtained when the parasitoid was reared on its original host for at least four generations. 相似文献
19.
Giuseppe Piccione Augusto Foà Cristiano Bertolucci Giovanni Caola 《Journal of circadian rhythms》2006,4(1):16-4
Background
In domestic animals many biochemical and physiological processes exhibit daily rhythmicity. The aim of the present study was to investigate the rhythmic pattern of salivary and serum urea concentrations in sheep. 相似文献20.
Gregory D Roach Kathryn J Reid Sally Ferguson Drew Dawson 《Journal of circadian rhythms》2006,4(1):8-5