Effects of phylogenetic associations on environmental and temporal niche partitioning among sympatric mammals

Mammals have evolved to occupy spatial and temporal niches in order to optimize resource utilization and minimize predation risk or competition. Subsequently, niche partitioning may be influenced by phylogenetic associations, which could have substantial consequences for ecosystem structure and function. We use the output from occupancy models based on camera trapping data to construct a tri-partite network describing the environmental and temporal partitioning of activity among twelve sympatric mammals in the Apennine Mountains of central Italy. We further evaluate if there were any effects of phylogenetic associations on the contributions of species to the properties of this spatio-temporal network. The Apennines form a pristine region in central Italy with a relatively intact Mediterranean mammal fauna. The mammal community in our study consisted of species ranging in size from 300 gs to over 200 kg, and included herbivores, omnivores and predators. There was limited structuring of the network describing environmental and temporal niche use. Furthermore, we did not find any phylogenetic signal in species contributions to network structures, and phylogenetic relatedness among species was not associated with their similarities in environmental or spatial niche use. However, animals appeared to have partitioned environmental niches more than temporal ones, suggesting that spatial variation in resource availability may have been more important than temporal avoidance of predation risk or competition in shaping activity within this mammal community. Our study highlights the need to evaluate under which conditions evolutionary history is influencing contemporary ecological processes

WOx/ZrO2 catalysts Part 4. Redox properties as investigated by redox cycles, XPS and EPR

The redox properties of wox/zro2 catalysts with W-content from 1.0 to 14.3 atoms nm-2, prepared by equilibrium adsorption from hydrous zirconium oxide and ammonium metatungstate solutions, were investigated by redox cycles with H2 and O2, volumetric oxygen adsorption at room temperature (RT), XPS and EPR. After catalysts were heated at 1073K in air, the various tungsten species (small WxOy clusters anchored to zirconia surface, polyoxotungstates species and crystalline WO3) reacted differently with H2 in the range 473-773K. The reduction degree of small W xOy clusters up to 723K slightly increased and then sharply increased, yielding at 773K an average oxidation state (nav) equal to 5.2. Conversely, the reduction degree of polyoxotungstates and WO 3 steeply increased from 523 to 773K, reaching nav equal to 4.8. XPS analysis disclosed that, after treatment in H2 at 773K, whereas W5+ formed on all the samples, W4+ species formed only in samples containing WO3 and polyoxotungstates. Depending on W-content, EPR detected various W5+ species in reduced ZW samples: isolated ions incorporated into the monoclinic zirconia; two kind of surface species, one in small clusters and the other in polyoxotungstates, resembling a bronze-like structure. The formation of O2 - by oxygen adsorption at RT gave an indirect evidence of isolated W5+ surface species, irrespective of W-content. Volumetric O2 adsorption indicated that W5+ surface species were largely re-oxidized at RT, whereas W4+ species, formed in polyoxotungstates and WO3, were less reactive, possibly because these species were less accessible to the gas phase. © 2004 Elsevier B.V. All rights reserved

Long-term practice effects on a new skilled motor learning: An electrophysiological study

Cortical functions concerned with the execution of skilled movements can be studied through complex interactive tasks. Skilled performance task (SPT) offers the greatest deal of information about the electrophysiological components reflecting pre-programming, execution of the movement and control of the results. Overall, these components are indicated as 'movement-related brain macropotentials' (MRBMs). Among them, Bereitschaftspotential (BP) reflects cerebral processes related to the preparation of movement and skilled performance positivity (SPP) reflects control processes on the result of performance. There is some evidence supporting a training effect on MRBMs, but less clear is whether long-term practice of a skilled activity could modify learning strategies of a new skilled task. We recorded MRBMs in subjects trained for a long time to perform a highly skilful athletic activity, i.e. gun shooting, and in a group of control-subjects without any former experience in skilled motor activities. Our findings demonstrated the existence of a relationship between pre-programming and performance control, as suggested by decrease of BP amplitude and increase of SPP amplitude in presence of high levels of performance. Long-term, practice seems to develop better control models on performance, that reduce the need of a high mental effort in pre-programming a skilled action. Copyright (C) 1996 Elsevier Science Ireland Ltd