Soil acidity, ecological stoichiometry and allometric scaling in grassland food webs

The factors regulating the structure of food webs are a central focus of community and ecosystem ecology, as trophic interactions among species have important impacts on nutrient storage and cycling in many ecosystems. For soil invertebrates in grassland ecosystems in the Netherlands, the site-specific slopes of the faunal biomass to organism body mass relationships reflected basic biochemical and biogeochemical processes associated with soil acidity and soil C : N : P stoichiometry. That is, the higher the phosphorus availability in the soil, the higher, on average, the slope of the faunal biomass size spectrum (i.e., the higher the biomass of large-bodied invertebrates relative to the biomass of small invertebrates). While other factors may also be involved, these results are consistent with the growth rate hypothesis from biological stoichiometry that relates phosphorus demands to ribosomal RNA and protein production. Thus our data represent the first time that ecosystem phosphorus availability has been associated with allometry in soil food webs (supporting information available online). Our results have broad implications, as soil invertebrates of different size have different effects on soil processes.     

Effect of temperature and sex on growth patterns in nymphs of the mayfly Hexagenia hilineata in the laboratory

SUMMARY. Eggs collected from Hexagenia bilineata females were successfully reared in the laboratory at temperatures of 15, 20, 25 and 30°C. Eggs did not hatch at 10°C and although hatching was successful at 35°C, all nymphs at this temperature died while in early instars.
Survival of nymphs between the approximate size interval of 4–14 mm showed a significant decrease with increased temperatures. Nymphs at 15°C, however, generally did not survive transformation to the subaduit stage.
The growth pattern of individual nymphs was well described by a logistic curve at most temperatures. Furthermore, growth pattern was significantly affected by both temperature and sex.
Rate of development from oviposition to first emergence increased with increasing temperatures in a linear fashion between 15 and 30°C. The relationship was equally well described by a hyperbolic equation and a power-law equation. By extrapolation from the hyperbolic equation, the lower threshold temperature for development was estimated to be 10.1°C3.1°C. The degree (°C)-days required for development from oviposition to first emergence was calculated to be 2337 days with 95% confidence limits of 2045–2727 days under laboratory conditions.     

The influence of climate and topography in patterns of territory establishment in a range‐expanding bird

The Dartford Warbler Sylvia undata has recently expanded its range northwards and upwards in the UK, consistent with the hypothesis that this cold‐sensitive species has responded to a warming climate. We interrogated distribution data, collected during four national surveys of this species between 1974 and 2006, to assess whether this large‐scale range expansion has been accompanied by finer‐scale changes in topographic characteristics of breeding locations. Within sites occupied in successive surveys, there was some evidence of limited altitudinal expansion between surveys. Within wider landscapes occupied in successive surveys, the preceding winter climate tended to be harsher at newly colonized sites than at sites that had already been occupied in the previous survey, while territories in newly colonized sites also tended to be on steeper slopes, especially if at higher altitude, and (in 1994 only) to be more south‐facing. Territories in sites that had already been occupied in the previous survey tended to be lower altitude, less steep and more north‐facing than territories in newly colonized landscapes. In 2006 only, the winter climate was significantly milder in newly colonized landscapes than in already occupied sites. The combined effects of a changing climate and topography may have influenced the pattern of in‐filling in the existing range, while colonization of distant areas, especially more latterly, may have been facilitated by a combination of increased dispersal pressure from the existing range and warming of climate which made higher altitude habitat in the new areas more suitable for occupancy. Careful consideration needs to be given to the importance of fine‐scale topographical variation in determining species’ responses to climate change in order to underpin robust adaptation strategies.     

Studies on plant growth-regulating substances XXVIII. Halogen-substituted benzoic acids

The plant growth-regulating activities of chloro-, bromo- and iodo-isomers in 2,5-, 2,3,5- and 2,3,6-substituted benzoic acids were assessed in the wheat cylinder, pea segment and pea curvature tests. Their effects in the tomato-leaf epinasty test were also investigated. Replacing an ortho-chloro atom by bromine had little or no effect on activity. An ortho-iodo substituent, however, reduced activity in the 2,3,6-substituted series and almost completely inhibited it in the 2,5- substituted series. This decreased activity of ortho-iodo-substituted isomers is visualized as being due to a steric inhibition of the attachment of the carboxyl group to its receptor unit prior to the initiation of the growth response.     

Nitrogen Assimilation in Barley (Hordeum vulgare L. cv. Mazurka) in Response to Nitrate and Ammonium Nutrition

Barley plants (Hordeum vulgare L. cv. Mazurka) were grown inaerated solution cultures with 2 mM or 8 mM inorganic nitrogensupplied as nitrate alone, ammonium alone or 1:1 nitrate+ammonium.Activities of the principal inorganic nitrogen assimilatoryenzymes and nitrogen transport were measured. Activities ofnitrate and nitrite reductases, glutamine synthetase and glutamatesynthase were greater in leaves than in roots but glutamatedehydrogenase was most active in roots. Only nitrate and nitritereductases changed notably (4–10 times) in response tothe different nitrogen treatments. Nitrate reductase appearedto be rate-limiting for nitrate assimilation to glutamate inroots and also in leaves, where its total in vitro activitywas closely related to nitrate flux in the xylem sap and wasslightly in excess of that needed to reduce the transportednitrate. Xylem nitrate concentration was 13 times greater thanthat in the nutrient solution. Ammonium nitrogen was assimilatedalmost completely in the roots and the small amount releasedinto the xylem sap was similar for the nitrate and the ammoniumtreatments. The presence of ammonium in the nutrient decreasedboth export of nitrate to the xylem and its accumulation inleaves and roots. Nitrate was stored in stem bases and was releasedto the xylem and thence to the leaves during nitrogen starvation.In these experiments, ammonium was assimilated principally inthe roots and nitrate in the leaves. Any advantage of this divisionof function may depend partly on total conversion of inorganicnitrogen to amino acids when nitrate and ammonium are givenin optimal concentrations. Hordeum vulgare L., barley, nitrate, ammonium, nitrate reductase, nitrite reductase, glutamine synthetase, glutamate synthase, glutamate dehydrogenase, nitrogen transport     

In situ ecological development of a bacteriogenic iron oxide-producing microbial community from a subsurface granitic rock environment

The initial development and diversity of an in situ subsurface microbial community producing bacteriogenic iron oxides (BIOS) were investigated at the initiation of biofilm growth (2‐month period) and after a 1‐year period of undisturbed growth. Water chemistry data, samples of iron encrusted biofilm material and groundwater were collected from BRIC (BIOS reactor, in situ, continuous flow) apparatuses installed 297 m below sea level at the Äspö Hard Rock Laboratory (HRL) in south eastern Sweden. Comparisons between the BIOS BRIC system and an anaerobic control (AC) BRIC revealed that water mixing at the inflow leads to profuse development of BIOS related to a slightly elevated level of O₂ (up to 0.3 mg L^?1 at the transition zone between BIOS development and non‐development) and elevated Eh (>120 mV) in the first 70 mm of water depth. Decreases in dissolved and particulate iron were connected to the visible appearance of BIOS biofilms. The basic phylogenetic diversity of this site was evaluated using amplified ribosomal DNA restriction enzyme analysis (ARDRA), denaturing gradient gel electrophoresis (DGGE) and partial sequencing of 16S rDNA. From 67 clones that were positive for 16S rDNA inserts, a total of 42 different ARDRA profiles were recognized, representing four bacterial phyla and 14 different metabolic lifestyles. DGGE profiles indicated that there are differences in the representative bacteria when considering either BIOS biofilms or groundwater. DGGE also indicated that the DNA extraction protocols and any polymerase chain reaction biases were consistent. Bacterial metabolic groups associated with indirect metal adsorption and reduction along with bacteria utilizing many alternative electron acceptors were strongly represented within the clones. This study indicates that the microbial diversity of BIOS is greater than previously thought.     

Antigenic Relationship Between Plasmodium falciparum and Babesia bovis: Reactivity with Antibodies to Culture-Derived Soluble Exoantigens1

Antigenic similarities between Plasmodium and Babesia parasites of the phylum Apicomplexa have been previously demonstrated primarily by the serological cross reactivity observed in the indirect fluorescent antibody (IFA) test. We have now studied the antigenic relationship between the human malaria parasite, Plasmodium falciparum, and the hemoparasitic agent of cattle, Babesia bovis, using rabbit monospecific antibodies produced against individual culture-derived P. falciparum polypeptides and bovine polyspecific antibodies to B. bovis exoantigens. These respective antibodies were found to be distinctly cross reactive in the IFA test using infected erythrocytes (squirrel monkey—P. falciparum; bovine—B. bovis) as antigen substrates. Immunofluorescence was shown to be highly specific for parasite surfaces. Additionally, the degree of reactivity with soluble exoantigens contained in Plasmodium and Babesia culture supernatants was monitored by a two-site enzyme immunoassay employing the cross-reactive antibodies. Further evidence for antigenic cross reactivity between P. falciparum and B. bovis parasites was shown with the in vitro inhibition assay. Antibodies to P. falciparum and B. bovis were found to be highly inhibitory for the in vitro growth of P. falciparum in human erythrocytes.     

Phylogenetic relationships in the iguanid lizard genus Liolaemus: multiple origins of viviparous reproduction and evidence for recurring Andean vicariance and dispersal

Phylogenetic relationships within the iguanid lizard genus Liolaemus are investigated using 1710 aligned base positions (785 phylogenetically informative) of mitochondrial DNA sequences, representing coding regions for eight tRNAs, ND2, and portions of ND1 and COL Sixty new sequences ranging in length from 1736 to 1754 bases are compared with four previously reported sequences. Liolaemus species form two well-supported monophyletic groups of subgeneric status, Liolaemus and Eulaemus. These subgenera appear to have separated at least 12.6 million years ago based on the amount of molecular evolutionary divergence between them. Hypotheses that species occurring in the Andes, west of the Andes, and east of the Andes, each comprise distinct monophyletic groups are independently rejected statistically. The shortest estimate of phylogeny suggests mat Liolaemus originated either in the Andes or the eastern lowlands. Numerous evolutionary shifts have occurred between the Andes, and the eastern and western lowlands, suggesting recurring vicariance and dispersal. Species occurring at high elevations or high latitudes usually have viviparous reproduction. Depending on whether parity mode is considered reversible in Liolaemus , the most parsimonious reconstruction supports at least six independent origins of viviparity or at least three gains followed by three losses of viviparity among die 60 Liolaemus lineages examined.     

A Companion to the Anthropology of Politics

A Companion to the Anthropology of Politics . David Nugent and Joan Vincent, eds. Malden, MA: Blackwell Publishing, 2004. 500 pp.     

Provisioning habitat with custom‐designed nest‐boxes increases reproductive success in an endangered finch

Manipulating resource availability to assess the strength and effects of resource limitation on an animal population is relatively straightforward, and thus, common in the scientific literature. Resource quality, however, is rarely manipulated, as this requires a priori knowledge of a relationship between some measurable variation in the resource and individual preference and/or fitness. Recent research on nest‐site selection was used to inform the design of custom‐built nest‐boxes for an endangered hollow‐nester, the Gouldian finch (Erythrura gouldiae). By provisioning breeding populations with these ‘high quality’ artificial nest sites over 3 years, we experimentally investigated the strength and effects of nest‐site limitation in this species. Breeding pairs using nest‐boxes initiated nesting earlier, produced larger clutches and fledged more offspring per season than those in natural hollows. Total and mean reproductive output also increased in nest‐box provisioned sites over the duration of the study. All of these effects were predominantly driven by pairs initiating clutches earlier, potentially because of the reduced intra‐ and interspecific competition for nest sites at optimal breeding times. Our findings suggest that reproduction in wild Gouldian finch populations may be limited by the availability of high quality nest sites in the landscape, and that nest‐boxes could be used as a tool for enhancing reproduction in recovering populations. Furthermore, we conclude that resource quality is equally, if not more important than quantity when supplementing resource‐limited habitats.