Dissecting the species–energy relationship

Environmental energy availability can explain much of the spatial variation in species richness. Such species–energy relationships encompass a diverse range of forms, and there is intense debate concerning which of these predominate, and the factors promoting this diversity. Despite this there has been relatively little investigation of whether the form, and relative strength, of species–energy relationships varies with (i) the currency of energy availability that is used, and (ii) the ecological characteristics of the constituent species. Such investigations can, however, shed light on the causal mechanisms underlying species–energy relationships. We illustrate this using the British breeding avifauna. The strength of the species–energy relationship is dependent on the energy metric used, with species richness being more closely correlated with temperature than the Normalized Difference Vegetation Index, which is a strong correlate of net primary productivity. We find little evidence, however, for the thermoregulatory load hypothesis that high temperatures enable individuals to invest in growth and reproduction, rather than thermoregulation, increasing population sizes that buffer species from extinction. High levels of productive energy may also elevate population size, which is related to extinction risk by a negative decelerating function. Therefore, the rarest species should exhibit the strongest species–energy relationship. We find evidence to the contrary, together with little support for suggestions that high-energy availability elevates species richness by increasing the numbers of specialists or predators

Species traits and the form of individual species–energy relationships

Environmental energy availability explains much of the spatial variation in species richness at regional scales. While numerous mechanisms that may drive such total species–energy relationships have been identified, knowledge of their relative contributions is scant. Here, we adopt a novel approach to identify these drivers that exploits the composite nature of species richness, i.e. its summation from individual species distributions. We construct individual species–energy relationships (ISERs) for each species in the British breeding avifauna using both solar (temperature) and productive energy metrics (normalized difference vegetation index) as measures of environmental energy availability. We use the slopes of these relationships and the resultant change in deviance, relative to a null model, as measures of their strength and use them as response variables in multiple regressions that use ecological traits as predictors. The commonest species exhibit the strongest ISERs, which is counter to the prediction derived from the more individuals hypothesis. There is no evidence that predatory species have stronger ISERs, which is incompatible with the suggestion that high levels of energy availability increase the length of the food chain allowing larger numbers of predators to exist. We find some evidence that species with narrow niche breadths have stronger ISERs, thus providing one of the few pieces of supportive evidence that high-energy availability promotes species richness by increasing the occurrence of specialist species that use a narrow range of resources

Summer Diet of the Bearded Seal (Erignathus barbatus) in the Canadian High Arctic

Stomach contents of 34 bearded seals taken in three High Arctic localities (Grise Fiord, Pond Inlet and Clyde) during the summers from 1978-1980 were examined. At least 12 species of fish were present but sculpins (Cottidae) and arctic cod (Boreogadus saida) comprised the bulk of the diet. Eelpouts (Lycodes spp.) and polar cod (Arctogadus glacialis) were also ingested in considerable amounts. In 15 of 19 stomachs containing > 1 kg food, fish contributed > 90% of the wet weight. The whelk Buccinem and the shrimp Sclerocrangon boreas accounted for most of the invertebrate component of the diet. Clams, cephalopods, anemones, sea cucumbers, polychaete worms and other invertebrates occurred in small amounts. The largest measured weight of stomach contents was 7.6 kg from a seal that had fed heavily on arctic cod. There were no significant differences amongst the three localities in the amount of food ingested; however, the proportions of arctic cod and sculpins varied considerably among localities. Bearded seals fed on the available size range of arctic cod but were limited to the smaller sculpins (<200 g), eelpouts (<200 g) and polar cod (<350 g).Key words: bearded seals, Canadian High Arctic, dietMots clés: phoques barbus, nord de l'Arctique canadien, régime alimentair

Prediction of microgeometrical influences on micropitting fatigue damage on 32CrMoV13 steel

Dr Fabre's sabbatical period at the Cardiff School of Engineering allowed the research to be conducted. Thanks are due to the M2P department of Arts et Métiers ParisTech, to Arts et Métiers ParisTech—Aix en Provence, and to the MécaSurf laboratory for supporting the visit financially, and to Cardiff University for provision of research facilities. Dr Sharif's contribution to the research was supported financially by UK Engineering & Physical Sciences Research Council (EPSRC) with Grant no. EP/G06024X/1.Micropitting is a form of surface fatigue damage that occurs in the gear teeth. It is due to the effect of variation in the mechanical loading in the contact zone between the two teeth, induced especially by flank roughness. In this study, generic roughness profiles were built with geometrical parameters to simulate the contact between two rough surfaces. Using elastohydrodynamic lubrication code and Crossland’s fatigue criteria, the influence on fatigue lifetime was analysed for changes in each parameter. The relevant parameters were determined that influence(i) the conventional pitting,(ii) the extent to which the von Mises equivalent stress exceeds the material yield stress in the zone where micropitting occurs, and(iii) the fatigue lifetime for steel teeth. With nitriding benefits, the same trends were shown with weaker effects

Applications of proxy system modeling in high resolution paleoclimatology

AbstractA proxy system model may be defined as the complete set of forward and mechanistic processes by which the response of a sensor to environmental forcing is recorded and subsequently observed in a material archive. Proxy system modeling complements and sharpens signal interpretations based solely on statistical analyses and transformations; provides the basis for observing network optimization, hypothesis testing, and data-model comparisons for uncertainty estimation; and may be incorporated as weak but mechanistically-plausible constraints into paleoclimatic reconstruction algorithms. Following a review illustrating these applications, we recommend future research pathways, including development of intermediate proxy system models for important sensors, archives, and observations; linking proxy system models to climate system models; hypothesis development and evaluation; more realistic multi-archive, multi-observation network design; examination of proxy system behavior under extreme conditions; and generalized modeling of the total uncertainty in paleoclimate reconstructions derived from paleo-observations

Effects of profile errors on lubrication performance of helical gears

Analysis of the elastohydrodynamic lubrication (EHL) of gears generally assumes that the tooth flanks are smooth surfaces. There is considerable interest in establishing the extent to which smooth surface analyses are distorted by the presence of surface roughness. The current paper concerns a different scale of deviation from the specified surface profile, namely involute profile error. The paper quantifies the deviation from the smooth surface behaviour using standard profile error measurements, and also considers how the means by which profile error is measured influences the outcome/conclusions. Transient EHL analyses of the meshing cycle of helical gears taking profile error data from a gear measuring machine are compared with analyses using equivalent measurements determined by the waviness from surface profilometer measurements

Effect of Temperature and Electrolyte Composition on the Susceptibility of Alloy 22 to Localized Corrosion

The study of the electrochemical behavior of Alloy 22 has been carried out in various concentrated environments using different sample configurations. Comparisons were made between the electrochemical behaviors of Alloy 22 in concentrated chloride solutions, and in concentrated chloride solutions with nitrate ions (NO{sub 3}{sup -}). In other experiments, the effect of fluoride ions (F{sup -}) was investigated. These comparative studies were performed at various temperatures. The rate of corrosion was found to increase with increase in temperature. The presence of nitrate ions reduced corrosion attack on Alloy 22. F{sup -} was found to be more benign to Alloy 22 compared with chloride ions (Cl{sup -}). However a combination of F{sup -} and Cl{sup -} was found to initiate deeper crevices compared with the only Cl{sup -} in the electrolyte

Pathogenic Potential to Humans of Bovine Escherichia coli O26, Scotland

Escherichia coli O26 and O157 have similar overall prevalences in cattle in Scotland, but in humans, Shiga toxin–producing E. coli O26 infections are fewer and clinically less severe than E. coli O157 infections. To investigate this discrepancy, we genotyped E. coli O26 isolates from cattle and humans in Scotland and continental Europe. The genetic background of some strains from Scotland was closely related to that of strains causing severe infections in Europe. Nonmetric multidimensional scaling found an association between hemolytic uremic syndrome (HUS) and multilocus sequence type 21 strains and confirmed the role of stx<sub>2</sub> in severe human disease. Although the prevalences of E. coli O26 and O157 on cattle farms in Scotland are equivalent, prevalence of more virulent strains is low, reducing human infection risk. However, new data on E. coli O26–associated HUS in humans highlight the need for surveillance of non-O157 enterohemorrhagic E. coli and for understanding stx<sub>2</sub> phage acquisition

Searching scale space for activation in PET images

Porter's lodg