Home range and habitat selection by the Nutcracker Nucifraga caryocatactes during autumn in the Alps

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.     

Effect of Gossypol upon Motility and Ultrastructure of Trypanosoma cruzi1

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.     

Thirty years of in situ tree growth under elevated CO2: a model for future forest responses?

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.     

A comparative analysis of the breeding biology of the Red-billed Chough Pynhocorax pyrrhocorax and the Alpine Chough P. graculus coexisting in the Alps

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.     

Geographic and temporal variation in the ant–seed dispersal assemblage of the perennial herb Helleborus foetidus L. (Ranunculaceae)

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.     

Effects of Cold and Nocodazole Treatments on the Microtubular Systems of Paramecium in Interphase

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.     

Production and Characterization of Three Polyclonal Antibodies Raised Against Cyst Wall Proteins of a Hypotrichous Ciliate

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.     

The Interface Between Air and Water: A Perturbation Source Eliciting Adaptive Behaviour in Ciliates

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.