Identifying landscape scale patterns from individual scale processes

Extrapolating across scales is a critical problem in ecology. Explicit mechanistic models of ecological systems provide a bridge from measurements of processes at small and short scales to larger scales; spatial patterns at large scales can be used to test the outcomes of these models. However, it is necessary to identify patterns that are not dependent on initial conditions, because small scale initial conditions will not normally be measured at large scales. We examined one possible pattern that could meet these conditions, the relationship between mean and variance in abundance of a parasitic tick in an individual based model of a lizard tick interaction. We scaled discrepancies between the observed and simulated patterns with a transformation of the variance–covariance matrix of the observed pattern to objectively identify patterns that are “close”.     

Effects of lead and selected pyrethroids/piperonyl butoxide alone and in combination on Na,K‐ATPase

In vitro effects of Pb²⁺, the pyrethroid insecticides cypermethrin, fenvalerate and the syner‐gist piperonyl butoxide on sodium‐potassium‐activated adenosine triphosphatase (Na,K‐ATPase) from dog kidney were determined. Pb²⁺ with an estimated IC50 value of 5.2 μM was found to be a potent inhibitor of Na,K‐ATPase activity, whereas Na,K‐ATPase was less sensitive to the pyrethroids tested and piperonyl butoxide. Investigation with circular dichroism (CD) spec‐troscopy showed that inhibition occurs through conformational changes of the α‐subunit of the enzyme. The kinetic characteristics of inhibition of Na,K‐ATPase with varying substrate (ATP) concentrations as well as with varying Na⁺ concentrations exhibited a competitive type of inhibition with Pb²⁺ in the μM range. With Pb²⁺ alone in the enzyme assay no conformational changes of the protein could be observed which confirmed the assumption that Pb²⁺ can bind to the Na⁺ binding site of the α‐subunit. Uncompetitive type of inhibition occurred with varied K⁺ concentrations demonstrating that this cation binding site is not affected directly by Pb²⁺.

Complete reversal of Pb²⁺ by DTT confirms that a possible target for interaction of this heavy metal ion with Na, K‐ATPase are specific SH groups.

Synergistic effects could only be determined with higher Pb²⁺ concentrations of 3, 5 and 7 μM plus piperonyl butoxide while all other combinations with this heavy metal plus organic substances where of the additive type. With CD spectroscopy also only additive effects were observed. These results demonstrate that higher concentrations of piperonyl butoxide favor the binding of Pb²⁺ to the Na⁺ binding site by conformational changes of the protein.     

Fragrant legs in Paysandisia archon males (Lepidoptera, Castniidae)

Paysandisia archon was accidentally introduced into Europe where it damages endemic and ornamental palms, also threatening the date palm from North Africa. Little was known about sex pheromones in the Castniidae day-flying moth before a recent paper that concluded on the absence of female sex pheromone in P. archon. A putative identification of a short-range male pheromone, present on fore- and hindwings, was reported. In this paper, we describe the original structure of the male androconia located on the tarsi of the mid-legs. The extracts of mid-legs were analysed by GC/MS and the chemical structure of the male androconia component was identified as E2,Z13-18:OH. After extraction in solvent, biological activity of the extracts was assessed by EAG. The chemistry and the morphology of the androconia reinforce the current classification of the Castniidae in the Cossoid/Sesioid assemblage and provide new information on the chemical ecology in day-flying Lepidoptera and suit the recent paper describing the courtship behaviour     

Predictive modelling of seabed habitats: case study of subtidal kelp forests on the coast of Brittany, France

Predictive modelling to map subtidal communities is an alternative to “traditional” methods, such as direct sampling, remote sensing and acoustic survey, which are neither time- nor cost-effective for vast expanses. The principle of this modelling is the use of a combination of environmental key parameters to produce rules to understand species distribution and hence generate predictive maps. This study focuses on subtidal kelp forests (KF) on the coast of Brittany, France. The most significant key parameters to predict KF frequency are (1) the nature of the substrate, (2) depth, (3) water transparency, (4) water surface temperature and (5) hydrodynamics associated with the flexibility of algae in a flow. All these parameters are integrated in a spatial model, built using a Geographical Information System. This model results in a KF frequency map, where sites with optimum key parameters show a deeper limit of disappearance. After validation, the model is used in the context of Climate Change to estimate the effect of environmental variation on this depth limit of KF. Thus, the effects of both an increase in water temperature and a decrease in its transparency could lead to the complete disappearance of KF.     

Temperature, salinity and growth rate dependences of Mg/Ca and Sr/Ca ratios of the skeleton of the sea urchin Paracentrotus lividus (Lamarck): an experimental approach

The skeletal Mg/Ca ratio of echinoderms is known to increase with temperature but the relation has never been established in controlled experimental conditions. The present study investigated the effect of temperature, salinity and growth rate on Mg/Ca and Sr/Ca ratios in calcite skeletons of juvenile sea urchins grown in experimental conditions. Mg/Ca ratio was positively related to temperature, increasing until a plateau at high but field occurring temperatures. It was not linked to salinity nor growth rate. We suggest that this plateau is due to properties of the organic matrix of mineralization and recommend to take it into account for the use of Mg/Ca as proxy of seawater Mg/Ca. Skeletal Sr/Ca ratio was mainly dependent on temperature and growth rate, as usually observed in calcite skeletons.     

Potential influence of confounding factors (size,salinity) on biomarkers in the sentinel species <Emphasis Type="Italic">Scrobicularia plana</Emphasis> used in programmes monitoring estuarine quality

Introduction  

To use biomarkers in monitoring programmes, potential confounding factors must be considered. In the clam Scrobicularia plana, the influence of size and salinity on biomarkers at different levels of biological organisation has been examined.