Population changes in Czech passerines are predicted by their life‐history and ecological traits

A species’ susceptibility to environmental change might be predicted by its ecological and life‐history traits. However, the effects of such traits on long‐term bird population trends have not yet been assessed using a comprehensive set of explanatory variables. Moreover, the extent to which phylogeny affects patterns in the interspecific variability of population changes is unclear. Our study focuses on the interspecific variability in long‐term population trends and annual population fluctuations of 68 passerine species in the Czech Republic, assessing the effects of eight life‐history and five ecological traits. Ordination of life‐history traits of 68 species revealed a life‐history gradient, from ‘r‐selected’ (e.g. small body mass, short lifespan, high fecundity, large clutch size) to ‘K‐selected’ species. r‐selected species had more negative population trends than K‐selected species, and seed‐eaters declined compared with insectivores. We suggest that the r‐selected species probably suffer from widespread environmental changes, and the seed‐eaters from current changes in agriculture and land use. Populations of residents fluctuated more than populations of short‐distance migrants, probably due to the effect of winter climatic variability. Variance partitioning at three taxonomic levels showed that whereas population trends, population fluctuations and habitat specialization expressed the highest variability at the species level, most life‐history traits were more variable at higher taxonomic levels. These results explain the loss of statistical power in the relationship between life histories and population trends after controlling for phylogeny. However, we argue that a lack of significance after controlling for phylogeny should not reduce the value of such results for conservation purposes.     

The Carbon Economy of Rubus chamaemorus L. I. Photosynthesis

Studies on the photosynthetic activity of Rubus chamaemorusL. in controlled environment conditions are reported. Theseshow that material collected from Moor House National NatureReserve, England has a photosynthetic light saturation pointof 100 J m^–2s^–1 (380–720 nm) and a temperatureoptimum for photosynthesis between 10 and 15 °C. A markeddecline in net CO₂ uptake is evident at temperatures in excessof 18 ° C; this persists for some time after return to anoptimum temperature regime. Leaves show rapid responses to changesin both light intensity and temperature, and show no evidenceof an endogenous rhythm in photosynthetic rate.     

Interaction of chemotactic factors with human macrophages: induction of transmembrane potential changes

The electrophysiology of chemotactic factor interaction with cultured human macrophages was investigated with standard intracellular recording techniques. In initial studies, E. coli endotoxin-activated serum, added to cell cultures during intracellular recordings, caused membrane hyperpolarizations which were greater than 30 s in duration, 10-50 mV in amplitude, and associated with decreased membrane resistance. Control serum produced smaller hyperpolarizations lasting 10-20 s and 5-30 m V in amplitude. Endotoxin-activated human serum deficient in the third complement component (C3) did not produce hyperpolarizations unless the serum was reconstituted with C3 before activation. Fractionation of normal activated serum by molecular seive chromatography (G-75 Sephadex) indicated that only fractions that eluted with an estimated molecular weight of 12,500 produced membrane potential changes. The active material that was chemotactic for the macrophages was identified as the small molecular weight cleavage product of C5, C5a, by heat stability (30 min at 56 degrees C) and inactivation by goat antisera to human C5 but not C3. 17 percent of macrophages stimulated with C5a exhibited a biphasic response characterized by a small (2-6 mV), brief (1-10 s) depolarization associated with a decreased membrane resistance preceding the larger and prolonged hyperpolarizations. Magnesium-ethylene glycol bis[β-aminoethyl ether]N,N'-tetraacetic acid (Mg [2.5 mM]-EGTA [5.0 mM]) blocked the C5a-evoked potential changes, whereas colchine (10(- 6)M) and cytochalasin B (3.0 μg/ml did not. Hydrocortisone sodium succinate (0.5 mg/ml) decreased the percentage of cells responding to C5a. In related studies, synthetic N-formyl methionyl peptide (f-met-leu-phe), which had chemotactic activity for cultured macrophages, produced similar membrane potential changes. Repeated exposure of macrophages to C5a or f- met-leu-phe resulted in desensitization to the same stimulus. Simultaneous photomicroscope and intracellular recording studies during macrophage stimulation with chemotactic factor demonstrated that the membrane potential changes preceded membrane spreading, ruffling, and pseudopod formation. These observations demonstrate that ion fluxes associated with membrane potential changes are early events in macrophage activation by chemotactic factors     

Morphological Constraints of Shoot Demography of a Clonal Plant: Extra- and Intravaginal Tillers of Festuca rubra

Abstract Festuca rubra forms tillers in two different ways: extravaginally and intravaginally. Demography of these two tiller types was observed in seventeen selected tussocks of Festuca rubra s.s. over four growing seasons. Extravaginal tillers were bigger at birth and on the average produced twice as many daughter tillers per tiller. In general, the natality and mortality of extravaginal tillers were less regular than that of intravaginal tillers. Overall tillering rate per tiller was correlated with the density of the surrounding vegetation; mortality, natality and tiller life span were not. High density of the surrounding vegetation did not result in increased formation of extravaginal tillers. The proportion of the extravaginal tillers was not correlated with the density of the F. rubra tussocks. There is no evidence for foraging by extravaginal tillers, but they do act as founders of small clusters of tillers.