Estimating diet in individual pumpkinseed sunfish Lepomis gibbosus using stomach contents,stable isotopes and parasites

The diets of 99 pumpkinseed sunfish Lepomis gibbosus from a pair of small, adjacent lakes in Ontario, Canada, were estimated from their stomach contents, trophically transmitted parasites and stable isotopes of carbon and nitrogen in fish tissue. The three methods provided virtually unrelated information. There was no significant correlation in the importance of any prey item across all three methods. Fish with similar diets according to one method of estimating diet showed no tendency to be similar according to other methods. Although there was limited variation in fish size and the spatial scale of the study was small, both fish size and spatial origin showed comparatively strong associations with diet data obtained with all three methods. These results suggest that a multidisciplinary approach that accounts for fish size and spatial origins is necessary to accurately characterize diets of individual fish.     

Nitrogen Utilization and Toxin Production by Two Diatoms of the Pseudo‐nitzschia pseudodelicatissima Complex: P. cuspidata and P. fryxelliana

The toxigenic diatom Pseudo‐nitzschia cuspidata, isolated from the U.S. Pacific Northwest, was examined in unialgal batch cultures to evaluate domoic acid (DA) toxicity and growth as a function of light, N substrate, and growth phase. Experiments conducted at saturating (120 μmol photons · m^?2 · s^?1) and subsaturating (40 μmol photons · m^?2 · s^?1) photosynthetic photon flux density (PPFD), demonstrate that P. cuspidata grows significantly faster at the higher PPFD on all three N substrates tested [nitrate (NO₃^?), ammonium (NH₄⁺), and urea], but neither cellular toxicity nor exponential growth rates were strongly associated with one N source over the other at high PPFD. However, at the lower PPFD, the exponential growth rates were approximately halved, and the cells were significantly more toxic regardless of N substrate. Urea supported significantly faster growth rates, and cellular toxicity varied as a function of N substrate with NO₃^?‐supported cells being significantly more toxic than both NH₄⁺‐ and urea‐supported cells at the low PPFD. Kinetic uptake parameters were determined for another member of the P. pseudodelicatissima complex, P. fryxelliana. After growth of these cells on NO₃^? they exhibited maximum specific uptake rates (V_max) of 22.7, 29.9, 8.98 × 10^?3 · h^?1, half‐saturation constants (K_s) of 1.34, 2.14, 0.28 μg‐at N · L^?1, and affinity values (α) of 17.0, 14.7, 32.5 × 10^?3 · h^?1/(μg‐at N · L^?1) for NO₃^?, NH₄⁺ and urea, respectively. These labo‐ratory results demonstrate the capability of P. cuspidata to grow and produce DA on both oxidized and reduced N substrates during both exponential and stationary growth phases, and the uptake kinetic results for the pseudo‐cryptic species, P. fryxelliana suggest that reduced N sources from coastal runoff could be important for maintenance of these small pennate diatoms in U.S. west coast blooms, especially during times of low ambient N concentrations.     

Effect of nitrogen fertilizer level on infestations of lepidopterous stemborers and yields of maize in Zanzibar

The effect of nitrogen levels of 0, 60, 120, and 250 kg/ha and insecticide treatment (Furadan) on population densities and parasitism of lepidopteran stemborers, and maize yields were studied in Zanzibar during 2004/05. Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) dominated by 3-fold over Sesamia calamistis Hampson (Lepidoptera: Noctuidae) and 42 fold over Chilo orichalcociliellus Strand (Lepidoptera: Crambidae). Stemborer density per plant and parasitism by Cotesia flavipes (Cameron) (Hymenoptera: Braconidae) increased with nitrogen application level. Percentage of bored internodes per plant caused by stemborer decreased with N levels during the short rainy season. Pesticide application reduced densities of all stemborer species during the short rainy season, when infestations were high. Maize yield increased 2 to 8 times with N level, compared to the zero treatment, but the effect was less pronounced in the protected plots.     

Microbial Dynamics and Diversity of Bacillus thuringiensis in Textile Effluent Polluted and Non-polluted Rice Field Soils of Orissa, India

Microbial diversity was assessed in the soils of non-polluted rice fields of Central Rice Research Institute and Choudwar, and textile effluent contaminated (about 30 years) rice fields of Choudwar about 4 years after cessation of pollution. The soils contained 0.62–1.01 % organic C and 0.07–0.12 % total N, and measured 6.18–8.24 pH and 0.6–2.68 mS/cm Eh which were more in the polluted Choudwar soil. The microbial populations (×10⁶ cfu/g soil) in the soils were: heterotrophs 1.21–10.9, spore formers 0.9–2.43, Gram (−)ve bacteria 4.11–8.0, nitrifiers 0.72–1.5, denitrifiers 0.72–2.43, phosphate solubilizers 0.14–0.9, asymbiotic nitrogen fixers 0.34–0.59, actinomycetes 0.07–0.11, fungi 0–0.5 and Bacillus thuringiensis (Bt) 0.4–0.61 which predominated in the polluted soil of Choudwar. The fungi were scarce in the polluted rice fields. The Bt isolates belonged to three motile and one non-motile group. Two motile Bt isolates were phenotyped as Bt subsp. sotto and israelensis, whereas, the non-motile isolate was Bt subsp. wahuensis. All Bt isolates produced extracellular protease, lipase and amylase enzymes. The microbial guilds had positive correlation among themselves, as well as, with soil physico-chemical characters but the fungi had negative relation and the nitrogen fixers were unrelated with the biotic and abiotic components.     

Patterns of density dependence in growth,reproduction and survival in the invasive freshwater snail Pomacea canaliculata in Japanese rice fields

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Macroinvertebrate community structure,secondary production and trophic‐level dynamics in urban streams affected by non‐point‐source pollution

1. Despite non‐point‐source (NPS) pollution being perhaps the most ubiquitous stressor affecting urban streams, there is a lack of research assessing how urban NPS pollution affects stream ecosystems. We used a natural experimental design approach to assess how stream macroinvertebrate community structure, secondary production and trophic structure are influenced by urban NPS pollution in six streams. 2. Differences in macroinvertebrate community structure and secondary production among sites were highly correlated with stream‐water specific conductivity and dissolved inorganic phosphorus (DIP) concentrations. Macroinvertebrate richness, the Shannon diversity index and the Shannon evenness index were all negatively correlated with specific conductivity. These patterns were driven by differences in the richness and production of EPT and other intolerant taxa. Production of the five most productive taxa, tolerant taxa, non‐insect taxa and primary consumers were all positively correlated with stream‐water DIP. 3. Despite the positive correlation between primary consumer production and DIP, there was no correlation between macroinvertebrate predator production and either total or primary consumer macroinvertebrate production. This was observed because DIP was positively correlated with the production of non‐insect macroinvertebrate taxa assumed to be relatively unavailable for macroinvertebrate predator consumption. After removing production of these taxa, we observed a strong positive correlation between macroinvertebrate predator production and production of available prey. 4. Our results suggest that urban NPS pollution not only affects macroinvertebrate community structure, but also alters secondary production and trophic‐level dynamics. Differences in taxon production in our study indicate the potential for altered energy flow through stream food webs and potential effects on subsidies of aquatic insect prey to riparian food webs.     

Computational design of short-chain dehydrogenase Gox2181 for altered coenzyme specificity

Short-chain dehydrogenase Gox2181 from Gluconobacter oxydans catalyzes the reduction of 2,3-pentanedione by using NADH as the physiological electron donor. To realize its synthetic biological application for coenzyme recycling use, computational design and site-directed mutagenesis have been used to engineer Gox2181 to utilize not only NADH but also NADPH as the electron donor. Single and double mutations at residues Q20 and D43 were made in a recombinant expression system that corresponded to Gox2181-D43Q and Gox2181-Q20R&D43Q, respectively. The design of mutant Q20R not only resolved the hydrogen bond interaction and electrostatic interaction between R and 2′-phosphate of NADPH, but also could enhance the binding with 2′-phophated of NADPH by combining with D43Q. Molecular dynamics simulation has been carried out to testify the hydrogen bond interactions between mutation sites and 2′-phosphate of NADPH. Steady-state turnover measurement results indicated that Gox2181-D43Q could use both NADH and NADPH as its coenzyme, and so could Gox2181-Q20R&D43Q. Meanwhile, compared to the wild-type enzyme, Gox2181-D43Q exhibited dramatically reduced enzymatic activity while Gox2181-Q20R&D43Q successfully retained the majority of enzymatic activity.     

Fifty years of Bird Study

Capsule Field ornithology is alive and well, and in the future can contribute much more in Britain and elsewhere.

Aims To review the progress of field ornithology in Britain in the context of Bird Study and the British Trust for Ornithology.

Methods An overview was taken of the main subject areas published in Bird Study to characterize progress over 50 years. Some quantification of data on the main bird organizations was performed.

ResultsKnowledge of status and trends of British birds has moved from the qualitative to generally well detailed quantitative over the past 50 years. Causes of distribution and changes are increasingly well understood in terms of habitat and of population processes. Behaviour and ecology have grown to be separate disciplines in their own right although birds have been major subjects of study within them. Migration studies have lagged somewhat in Britain but advanced elsewhere in recent decades. Amongst the main bird organizations, the BTO still has a growing membership, that of the RSPB has reached an astonishing level but may be nearing a plateau while the BOU's membership is clearly in decline.

Conclusions Field ornithology has made a large contribution to the environmental debate and the future is set for further integration across disciplines in answering large-scale questions. Great public interest has supported the growth of ornithology with a big switch from amateur to professional workers. There is a major challenge to exploit the value of birds in promoting interest in the environment and delivering sound facts to support the biodiversity debate elsewhere on Earth. Fifty years of history in Britain indicate what is possible.     

TOWARDS A GENERAL THEORY OF GROUP SELECTION

The longstanding debate about the importance of group (multilevel) selection suffers from a lack of formal models that describe explicit selection events at multiple levels. Here, we describe a general class of models for two‐level evolutionary processes which include birth and death events at both levels. The models incorporate the state‐dependent rates at which these events occur. The models come in two closely related forms: (1) a continuous‐time Markov chain, and (2) a partial differential equation (PDE) derived from (1) by taking a limit. We argue that the mathematical structure of this PDE is the same for all models of two‐level population processes, regardless of the kinds of events featured in the model. The mathematical structure of the PDE allows for a simple and unambiguous way to distinguish between individual‐ and group‐level events in any two‐level population model. This distinction, in turn, suggests a new and intuitively appealing way to define group selection in terms of the effects of group‐level events. We illustrate our theory of group selection by applying it to models of the evolution of cooperation and the evolution of simple multicellular organisms, and then demonstrate that this kind of group selection is not mathematically equivalent to individual‐level (kin) selection.     

Structure of an atypical periplasmic adaptor from a multidrug efflux pump of the spirochete Borrelia burgdorferi

Periplasmic adaptor proteins are essential components of bacterial tripartite multidrug efflux pumps. Here we report the 2.35 Å resolution crystal structure of the BesA adaptor from the spirochete Borrelia burgdorferi solved using selenomethionine derivatized protein. BesA shows the archetypal linear, flexible, multi-domain architecture evident among proteobacteria and retains the lipoyl, β-barrel and membrane-proximal domains that interact with the periplasmic domains of the inner membrane transporter. However, it lacks the α-hairpin domain shown to establish extensive coiled-coil interactions with the periplasmic entrance helices of the outer membrane-anchored TolC exit duct. This has implications for the modelling of assembled tripartite efflux pumps.