Nitrogen deposition interacts with climate in affecting production and decomposition rates in Sphagnum mosses

Increasing rates of atmospheric nitrogen (N) deposition may reduce growth and accelerate decomposition of Sphagnum mosses in bogs. Sphagnum growth and rates of Sphagnum litter decomposition may also vary because of climate change as both processes are controlled by climatic factors. The initial purpose of this study was to assess if growth and litter decomposition of hummock and lawn Sphagnum species varied with increasing N input in a factorial mid‐term (2002–2005) experiment of N and phosphorus (P) addition, in a bog on the southern Alps of Italy. However, as the experimental period was characterized by an exceptional heat wave in summer 2003, we also explored the interacting effects of fertilization and strongly varying climate on growth and decomposition rates of Sphagnum. The heat wave implied strong dehydration of the upper Sphagnum layer even if precipitation in summer 2003 did not differ appreciably from the overall mean. Sphagnum production was somewhat depressed by high levels (3 g m⁻² yr⁻¹) of N addition without concomitant addition of P presumably because of nutrient imbalance in the tissues, but production rates were much lower than the overall means in 2003, when no effect of nutrient addition could be observed. Adding N at high level also increased the potential decay of Sphagnum litter. Higher CO₂ emission from N‐fertilized litter was due to amelioration of litter chemistry showing lower C/N quotients in the N‐fertilized treatments. Rates of CO₂ emission from incubated litter also were more strongly affected by water content than by nutrient status, with practically no CO₂ emission detected when litter was dry. We conclude that higher rates of atmospheric N availability input may depress Sphagnum growth because of P, and presumably potassium, (co‐)limitation. Higher N availability is also expected to promote potential decay of Sphagnum litter by ameliorating litter chemistry. However, both effects are less pronounced if the growing Sphagnum apex and the underlying senescing tissues dry out.     

Taxonomy, evolutionary biology and biogeography of South West European Polyommatus coridon (Lepidoptera: Lycaenidae)

Genetic relationships among 15 South West European populations of Polyommatus coridon were evaluated by the electrophoretic study of 16 gene-enzyme systems. Nei's indexes I and D and other statistics demonstrated that two different species are involved, identifiable as Polyommatus coridon (six populations from Southern France and Italy) and Polyommatus caelestissimus (nine populations from Spain), respectively. The Spanish complex is characterized by a different genetic balance, involving much higher degree of interdemic differentiation. It also differs from populations from France and Italy on one alternative locus showing complete fixation. Species-level distinction is independent of haploid chromosome numbers that vary from 87 to 88 in both groups. An evaluation of selective pressures as operated by climatic factors was attempted. The Pleistocene radiation of this group and consequent patterns of the gene flow were reconstructed using spatial autocorrelation analysis.     

Cytochemical Study on the Dormancy-imposing Endosperm of Cercis siliquastrum

Cytochemical observations indicate the occurrence of leucoanthocyanidinsin the protein bodies of Cercis siliquastrum endosperm; theendosperm cell walls give a positive Mayer's test, indicatingmucopolysac-charides. These results are discussed in relationto the endosperm-imposed dormancy of the seed. Cercis siliquastrum, endosperm-imposed dormancy, leucoanthocyanidins, mucopolysac-charides     

Action Mechanisms of the Secondary Metabolite Euplotin C: Signaling and Functional Role in Euplotes

ABSTRACT. Among secondary metabolites, the acetylated hemiacetal sesquiterpene euplotin C has been isolated from the marine, ciliated protist Euplotes crassus, and provides an effective mechanism for reducing populations of potential competitors through its cytotoxic properties. However, intracellular signaling mechanisms and their functional correlates mediating the ecological role of euplotin C are largely unknown. We report here that, in E. vannus (an Euplotes morphospecies that does not produce euplotin C and shares with E. crasssus the same interstitial habitat), euplotin C rapidly increases the intracellular concentration of both Ca²⁺ and Na⁺, suggesting a generalized effect of this metabolite on cation transport systems. In addition, euplotin C does not induce oxidative stress, but modulates the electrical properties of E. vannus through an increase of the amplitude of graded action potentials. These events parallel the disassembling of the ciliary structures, the inhibition of cell motility, the occurrence of aberrant cytoplasmic vacuoles, and the rapid inhibition of phagocytic activity. Euplotin C also increases lysosomal pH and decreases lysosomal membrane stability of E. vannus. These results suggest that euplotin C exerts a marked disruption of those homeostatic mechanisms whose efficiency represents the essential prerequisite to face the challenges of the interstitial environment.     

Behaviour and stress response during capture and handling of the red-billed chough Pyrrhocorax pyrrhocorax (Aves: Corvidae)

We studied the effect of capture and handling on free-living red-billed choughs Pyrrhocorax pyrrhocorax . We analysed the association between bird behavioural response and individual health, breeding status, sex, and age. Active responses (aggression towards the ringer, screaming) were more common in the breeding period, and in individuals with a high heterophils to lymphocytes ratio, indicating poor physiological condition and/or high chronic stress. Adults were more aggressive than juveniles and yearlings, and females were more aggressive than males. Sex, age, and condition differences were also recorded in the spectrotemporal output of distress calls. Birds with a screaming/active response appeared to be more stress-susceptible than passive and silent individuals, and this response was stronger during the energy demanding period of reproduction. The results obtained suggest that the response of the red-billed chough during capture might primarily reflect stress-susceptibility, although a number of potential alternative explanations are discussed.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 846–855.