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71.
72.
Home range and habitat selection by the Nutcracker Nucifraga caryocatactes during autumn in the Alps
ANTONIO ROLANDO 《Ibis》1996,138(3):384-390
In the Mont Avic Natural Park (NW Italian Alps), the Nutcracker Nucifraga caryocatactes occurred in coniferous forests where Arolla Pines Pinus cembra, its preferred habitat, were absent. A radiotelemetric study carried out during autumn 1992 and 1993 showed that, from September, Nutcrackers concentrated in the few Hazel Corylus avellana hedges of the rural zones of the park to collect nuts, which were eaten or stored. Individual home ranges overlapped to a high degree until October, when birds started to abandon the Hazel areas. From October onward, individual home ranges significantly expanded and their degree of overlap diminished compared to September. The home range analysis and the observations in the field suggested that the population of Nutcrackers in the park during autumn was made up of at least three different categories of birds, which displayed different ranging behaviour patterns. A few untagged birds probably stored nuts in their breeding territories, whereas all the radio-tagged birds ( n = 15) gave no indication of territorial use, since from October they either stored nuts in the coniferous woods near the Hazel hedges or abandoned the park to fly to other Hazel areas. Hence, during autumn the ranging behaviour of the Nutcrackers seems to be largely independent of their reproductive territorial system. Habitat selection analysis and transect counts revealed that birds positively selected Hazels, especially in the coniferous woods around Hazel hedges, and avoided the other coniferous forests. Nevertheless, from October some individuals reversed their habitat choices and positively selected coniferous forests (especially Mountain Pine Pinus uncinata woods) while avoiding Hazel. 相似文献
73.
ANTONIO BLANCO AGUSTIN AOKI ENRIQUE E. MONTAMAT LEONOR E. ROVAI 《The Journal of eukaryotic microbiology》1983,30(4):648-651
Gossypol, a polyphenolic compound from the cotton plant, immobilizes and structurally alters cultured Trypanosoma cruzi epimastigotes. Ultrastructural changes observed in gossypol-treated parasites were first detected in the kinetoplast and mitochondrion. At 50 μM concentration, much disorganization was evident after 5 min of incubation. With 25 μM gossypol, the same effect occurred after 30 min. Most epimastigotes were rounded, containing various membranous structures that could not be related to known cell components. 相似文献
74.
Thirty years of in situ tree growth under elevated CO2: a model for future forest responses? 总被引:4,自引:0,他引:4
STEPHAN HÄTTENSCHWILER FRANCO MIGLIETTA ANTONIO RASCHI & CHRISTIAN KÖRNER 《Global Change Biology》1997,3(5):463-471
Rising concentrations of atmospheric carbon dioxide have been predicted to stimulate the growth of forest trees. However, long-term effects on trees growing to maturity and to canopy closure while exposed to elevated CO2 have never been examined. We compared tree ring chronologies of Mediterranean Quercus ilex which have been continuously exposed to elevated CO2 (around 650 μmol mol–1) since they were seedlings, near two separate natural CO2 springs with those from trees at nearby ambient-CO2‘control’ sites. Trees grown under high CO2 for 30 years (1964–93) showed a 12% greater final radial stem width than those growing at the ambient-CO2 control sites. However, this stimulation was largely due to responses when trees were young. By the time trees were 25–30 y old the annual difference in tree ring width between low and high CO2 grown trees had disappeared. At any given tree age, elevated CO2 had a relatively greater positive effect on tree ring width in years with a dry spring compared to years with more rainfall between April and May. This indicates a beneficial effect of elevated CO2 on tree water relations under drought stress. Our data suggest that the early regeneration phase of forest stands can be accelerated in CO2-enriched atmospheres and that maximum biomass per land area may be reached sooner than under lower CO2 concentrations. In our study, high CO2 grown Q. ilex trees reached the same stem basal area at the age of 26 y as control trees at 29 y, i.e. three years earlier (faster turnover of carbon?). Reliable predictions of the future development of forests need to account for the variable responses of trees over their entire lifetime. Such responses to elevated CO2 can presently only be assessed at such unique field sites. 相似文献
75.
We compare the breeding biology of a small population of Red-billed Chough Pyrrhocorax pynhocorax with that of the Alpine Chough P. graculus coexisting in the western Italian Alps. The analysis focused on nest site choice, timing of breeding, reproductive success and parental effort (assessed by means of behavioural indices such as food provisioning rates and time budgets inside and close to the nest). The Alpine Chough nested in a greater variety of sites: natural cliffs, windows of a dam, pot-holes and abandoned buildings; the Red-billed Chough used only natural cliffs. Laying dates also differed significantly, with the Red-billed Chough breeding one month earlier than its congener. Differences in the feeding ecology of those species might be responsible for the observed temporal partitioning, thus facilitating coexistence. Breeding success and reproductive behaviour were similar, and the species differed in only one out of eight breeding parameters. It is suggested that similar strong constraints on breeding behaviour have resulted in the similarities in behaviour seen in these species. 相似文献
76.
ANTONIO J. MANZANEDA PEDRO J. REY RAPHAËL BOULAY 《Biological journal of the Linnean Society. Linnean Society of London》2007,92(1):135-150
Spatio-temporal variations in the composition of the animal interactive assemblages may result in variations in selective pressures on the plants. In ant–seed dispersal mutualisms, the study of the magnitude of spatial and temporal variation of ant assemblages is rarely studied, limiting inferences and generalizations on the evolution of this mutualism. Here, we describe the ant–disperser assemblage of the myrmecochorous herb Helleborus foetidus in 14 populations across the Iberian Peninsula, and dissect the variation in the assemblage into spatial and temporal components as a first step to evaluate the evolutionary potential of this interaction. The ant–visitor assemblage of H. foetidus was mainly represented by species of Formicinae and it was highly diverse and variable in composition and function. Ants behaving as legitimate dispersers and those with mixed behaviour numerically dominated the assemblage compared with elaiosome consumers. The magnitude of the spatial variation was higher than the temporal variation, suggesting that the relative frequency of each functional group will be more foreseeable among years in each population than among populations. At the expense of further analysis of the effects of such variation on dispersal success, we can envisage a selection mosaic scenario, where local adaptive responses of plants might arise as a result of local variations in the specific composition and function of the assemblage. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 135–150. 相似文献
77.
The sensitivity of the microtubular systems to cold and nocodazole treatments as well as the cellular distribution of microtubules containing acetylated a-tubulin have been studied in Paramecium. Our results indicate that the microtubular systems of Paramecium show marked differences in stability. Cold and nocodazole treatments produce the depolymerization of the major part of the cytoplasmic microtubular network while the cortical structures remain stable under treatment. This differential stability of the microtubular systems is associated with the acetylation of the a-tubulin. The use of the antibody 6-11B-1, specific for acetylated α-tubulin, shows that the microtubular systems containing acetylated a-tubulin are the same as those that remain stable after depoly-merizing treatments. Finally, the images obtained during the repolymerization by heating suggest that the cortical dikinetids are able to nucleate the microtubules of the cytoplasmic network. 相似文献
78.
ROSA M. RIOS JESUS MARTIN ANTONIO TORRES CONCEPCION FEDRIANI 《The Journal of eukaryotic microbiology》1992,39(5):584-588
ABSTRACT Three polyclonal antibodies raised against Paraurostyla sp. cyst wall polypeptides of molecular weight 110,000 (p110), 66,000 (p66) and 52,000 (p52) have been obtained. The specificity of the antisera was tested by immunoblotting. Anti-p110 antibody detected five bands of 300, 170, 135, 110 and 40 kDa, respectively. Antiserum obtained against p66 recognized only this protein. Anti-p52 antiserum showed reaction for two different bands of 52 and 44 kDa, respectively. The precise localization of these proteins in the cyst wall was assessed by light microscope immunocytochemistry. Anti-p110 antiserum produced a strong positive reaction in both the ectocyst and endocyst. Both anti-p66 and anti-p52 antibodies recognized the ectocyst. 相似文献
79.
NICOLA RICCI FABRIZIO ERRA ANTONIO RUSSO ROSALBA BANCHETTI Water-Air Interface 《The Journal of eukaryotic microbiology》1992,39(4):521-525
ABSTRACT Interference with the water-air interface, both direct (by contact with a flat, rigid surface) and indirect (by inducing a meniscus) caused the ciliated protozoa we investigated to actively collect in the water column or on the substrate directly under the area of altered surface tension. A crowding effect is observed in this "rest area" reaching plateau values within one hour after onset of the experiment. The simple experimental procedures described here induced analogous behaviour in both Paramecium caudatum (a swimmer) and Oxytricha bifaria (a crawler). The ciliates seem in this reaction to be seeking a refuge from vibrations transmitted by the free interface. Our discovery is discussed in its implications for the adaptive biology and ecology of these micro-organisms. 相似文献
80.
DAVID A. ANDOW JULIANO R. FARIAS RENATO J. HORIKOSHI DANIEL BERNARDI ANTONIO R. B. NASCIMENTO CELSO OMOTO 《Ecological Entomology》2015,40(3):229-236
1. Antagonistic interactions in herbivorous insects are often density‐dependent, so rates are predicted to vary dynamically over time as density changes. Fatal intraspecific interactions, especially cannibalism, occur between equal‐aged larvae in young first‐ and second‐instar Spodoptera frugiperda (J.E. Smith). 2. A cannibalism experiment was conducted, starting with seven different densities of neonate S. frugiperda larvae, each replicated 50 times. Larvae were examined daily for the duration of the first and second instars (7 days). Seven‐day mortality was density‐dependent. 3. A stochastic mathematical model was developed in which per‐capita mortality from antagonistic interactions among equal‐aged larvae varies dynamically as density changes. A maximum likelihood method was developed to estimate the conditional per‐capita mortality rate from antagonistic interactions given an intraspecific encounter. An alternative model with mean‐mortality from antagonistic interactions that depends only on the initial larval density was also developed. 4. The models were fitted to the experimental data, and compared using log‐likelihood. The dynamic model fitted the cannibalism data significantly better than the time‐averaged mortality model for all starting densities for the experimental data, implying that density‐dependent mortality varied dynamically over time even within short 7‐day periods. 5. The conditional per‐capita mortality rate from antagonistic interactions was also density‐dependent, possibly because encounters became more aggregated at higher density, or because the probability that a larva died from the interaction was higher at higher density, or both. 相似文献