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1. Competition by dominant species is thought to be key to structuring ant communities. However, recent findings suggest that the effect of dominant species on communities is less pronounced than previously assumed. 2. The aim of the present study was to identify the role of dominant ants in the organisation of Mediterranean communities, particularly the role of competition in invaded and uninvaded communities. The effects on ant assemblages of two dominant ants, the invasive Argentine ant and the native ant, Tapinoma nigerrimum Nylander, were assessed. 3. The abundances of both dominant ants were significantly correlated with a decrease in native ant richness at traps. However, only the invasive ant was associated with a reduction in diversity and abundance of other ant species at site scale. In the presence of T. nigerrimum, species co‐occurrence patterns were segregated or random. Community structure in both the dominant‐free and the Argentine ant sites showed random patterns of species co‐occurrence. 4. The present findings indicate that dominant ants regulate small‐scale diversity by competition. However, at the broader scale of the assemblage, T. nigerrimum may only affect species distribution, having no apparent effect on community composition. Moreover, we find no evidence that inter‐specific competition shapes species distribution in coastal Mediterranean communities free of dominant ants. 5. These results show that dominant species may affect ant assemblages but that the nature and the intensity of such effects are species and scale dependent. This confirms the hypothesis that competitive dominance may be only one of a range of factors that structure ant communities. 相似文献
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FRANCK BAMEUL 《Systematic Entomology》1992,17(1):1-20
Abstract. Eight new species of Psalitrus are described: P.besucheti, P.coccinelloides, P.decoratus and P.silvestris from Southern India and P.loebli, P.mahanuwara, P.serendibensis and P.veddha from Sri Lanka. The two Psalitrus known previously from India, P.championi and P.fallax , are redescribed and lectotypes and paralectotypes are designated. For each species the aedeagus and female ectodermal genitalia are figured. For the first time among Hydrophiloidea species characters have been found in female ectodermal genitalia, thanks to staining with chlorazol black dye. The best biometric characters are selected by multiple-discriminant analysis and an identification key is given. A list of the known Psalitrus species is given. 相似文献
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Vulnerability to drought‐induced cavitation in poplars: synthesis and future opportunities 下载免费PDF全文
RÉGIS FICHOT FRANCK BRIGNOLAS HERVÉ COCHARD REINHART CEULEMANS 《Plant, cell & environment》2015,38(7):1233-1251
Vulnerability to drought‐induced cavitation is a key trait of plant water relations. Here, we summarize the available literature on vulnerability to drought‐induced cavitation in poplars (Populus spp.), a genus of agronomic, ecological and scientific importance. Vulnerability curves and vulnerability parameters (including the water potential inducing 50% loss in hydraulic conductivity, P50) were collected from 37 studies published between 1991 and 2014, covering a range of 10 species and 12 interspecific hybrid crosses. Results of our meta‐analysis confirm that poplars are among the most vulnerable woody species to drought‐induced cavitation (mean P50 = ?1.44 and ?1.55 MPa across pure species and hybrids, respectively). Yet, significant variation occurs among species (P50 range: 1.43 MPa) and among hybrid crosses (P50 range: 1.12 MPa), within species and hybrid crosses (max. P50 range reported: 0.8 MPa) as well as in response to environmental factors including nitrogen fertilization, irradiance, temperature and drought (max. P50 range reported: 0.75 MPa). Potential implications and gaps in knowledge are discussed in the context of poplar cultivation, species adaptation and climate modifications. We suggest that poplars represent a valuable model for studies on drought‐induced cavitation, especially to elucidate the genetic and molecular basis of cavitation resistance in Angiosperms. 相似文献
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Two-d-old leaves which do not contain prolamellar bodies synthesizeactive protochlorophyllide in darkness. When protochlorophyllideis photoreduced by one intense white flash, a main chlorophyllidespecies emitting at 690 nm is formed. After the photoreduction,the emission maximum is shifted to 675 nm within 5s. This resultsuggests that in young leaves, chlorophyllide formed after oneflash is quickly released from the active site of NADPH: protochlorophyllideoxidoreductase. This interpretation is strenghtened by time-resolvedfluorescence measurements at room temperature, showing that675 nm emitting chlorophyllide does not transfer excitationenergy to the 696 nm emitting chlorophyllide which is formedin very low amount. In 10-d-old bean leaves, the 690 nm chlorophyllideemitting species formed after one short flash undergoes thewellknown rapid and Shibata spectral shifts. The 675 nm emittingchlorophyllide appears only as a shoulder. At both ages, thefluorescence intensity of the active protochlorophyllide stronglydecreases during and after photoreduction, suggesting rapidmodifications in the close environment of the pigment. Key words: Bean, chlorophyllide, etioplast, proplastid, protochlorophyllide 相似文献
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YOLANTA SAKS YEHOSHUA WAKS BATIA WEISS ANDRE FRANCK EDO CHALUTZ 《The Annals of applied biology》1988,113(2):375-381
Regreening was observed and measured in harvested pummelo fruit stored in the light. At temperatures of 22 - 28°C, regular daylight was sufficient for regreening to occur. The addition of continuous fluorescent light intensified the process. Pre-stored fruit held in darkness at 11°C and non-stored fruit responded to both light conditions in a similar manner. Electron microscopy has shown that globular chromoplasts revert to chloroplasts during regreening. The similarities between regreening processes in preharvest and postharvest fruits are discussed. 相似文献
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