Unnatural selection of salmon life histories in a modified riverscape

Altered river flows and fragmented habitats often simplify riverine communities and favor non‐native fishes, but their influence on life‐history expression and survival is less clear. Here, we quantified the expression and ultimate success of diverse salmon emigration behaviors in an anthropogenically altered California river system. We analyzed two decades of Chinook salmon monitoring data to explore the influence of regulated flows on juvenile emigration phenology, abundance, and recruitment. We then followed seven cohorts into adulthood using otolith (ear stone) chemical archives to identify patterns in time‐ and size‐selective mortality along the migratory corridor. Suppressed winter flow cues were associated with delayed emigration timing, particularly in warm, dry years, which was also when selection against late migrants was the most extreme. Lower, less variable flows were also associated with reduced juvenile and adult production, highlighting the importance of streamflow for cohort success in these southernmost populations. While most juveniles emigrated from the natal stream as fry or smolts, the survivors were dominated by the rare few that left at intermediate sizes and times, coinciding with managed flows released before extreme summer temperatures. The consistent selection against early (small) and late (large) migrants counters prevailing ecological theory that predicts different traits to be favored under varying environmental conditions. Yet, even with this weakened portfolio, maintaining a broad distribution in migration traits still increased adult production and reduced variance. In years exhibiting large fry pulses, even marginal increases in their survival would have significantly boosted recruitment. However, management actions favoring any single phenotype could have negative evolutionary and demographic consequences, potentially reducing adaptability and population stability. To recover fish populations and support viable fisheries in a warming and increasingly unpredictable climate, coordinating flow and habitat management within and among watersheds will be critical to balance trait optimization versus diversification.     

Interior Least Tern (Sternula antillarum) breeding distribution and ecology: implications for population‐level studies and the evaluation of alternative management strategies on large,regulated rivers

Interior Least Terns (Sternula antillarum) (ILT) are colonial, fish‐eating birds that breed within active channels of large sand bed rivers of the Great Plains and in the Lower Mississippi Valley. Multipurpose dams, irrigation structures, and engineered navigation systems have been present on these rivers for many decades. Despite severe alteration of channels and flow regimes, regulation era floods have remained effective at maintaining bare sandbar nesting habitat on many river segments and ILT populations have been stable or expanding since they were listed as endangered in 1985. We used ILT breeding colony locations from 2002 to 2012 and dispersal information to identify 16 populations and 48 subpopulations. More than 90% of ILT and >83% of river km with suitable nesting habitat occur within the two largest populations. However, replicate populations remain throughout the entire historical, geophysical, and ecological range of ILT. Rapid colonization of anthropogenic habitats in areas that were not historically occupied suggests metapopulation dynamics. The highest likelihood of demographic connectivity among ILT populations occurs across the Southern Plains and the Lower Mississippi River, which may be demographically connected with Least Tern populations on the Gulf Coast. Paired ecological and bird population models are needed to test whether previously articulated threats limit ILT population growth and to determine if management intervention is necessary and where. Given current knowledge, the largest sources of model uncertainty will be: (1) uncertainty in relationships between high flow events and subsequent sandbar characteristics and (2) uncertainty regarding the frequency of dispersal among population subunits. We recommend research strategies to reduce these uncertainties.     

Pyrimidine-fused heterocycle derivatives as a novel class of inhibitors for α-glucosidase

The needs for diverse inhibitors of α-glucosidase (α-Gls) encouraged us to synthesize five different poly-hydroxy functionalized pyrimidine-fused heterocyclic (PHPFH) molecules, having either aliphatic or aromatic side chains (C₁–C₅) and their inhibitory activities were examined spectroscopically against yeast and mouse intestinal α-Gls. The results revealed that aromatic substitution of the synthetic compounds has significant impact on their inhibitory properties. Moreover C₃ with the substituted moiety as 4-(4-aminophenylsulfonyl) phenyl (4-APSP) revealed strong inhibitory activity with non-competitive and competitive inhibition modes against yeast and mouse α-Gls, respectively. Furthermore, in the presence of increasing concentration of C₃, both Trp and 1-anilinonaphthalene-8-sulfonic acid (ANS) fluorescence intensities of yeast α-Gls were gradually decreased, suggesting that C₃ binding induced significant structural alteration which was accompanied with the reduction of hydrophobic surfaces. Also, the interaction between yeast α-Gls and C₃ was proved to be spontaneous and driven mainly by hydrophobic forces. Overall, this study suggests that aromatic substitution on pyrimidine-fused heterocyclic (PFH) scaffold may represent a novel class of promising inhibitors of α-Gls.     

Lipid peroxidation contributes to age-related membrane rigidity

The aim of this work was to assess the relative contributions of lipid peroxidation and cholesterol content to the increase in membrane rigidity observed during senescence. Membrane fluidity was manipulated through exposure to peroxidized or cholesterol-loaded liposomes. Small unilamella liposomes were prepared and either peroxidized by Fe⁺⁺-ADP-ascorbic acid or loaded with cholesterol. After incorporation of the liposomes into rat liver microsomal membranes, membrane fluidity was quantitated by measuring changes in polarization. Membranes exhibited a greater sensitivity to peroxidation than cholesterol in that incorporation of peroxidized liposomes induced microsomal membrane rigidity substantially more than did cholesterol-loaded liposomes. Thus it is proposed, based on data from the present and earlier studies, that membrane fluidity can be modulated readily by lipid peroxidation of membrane phospholipids, irrespective of the influences of cholesterol. These results support the proposal that alterations of lipid structure are more potent and effective than compositional changes in cholesterol in inducing age-related increases in membrane rigidity.     

The role of citrate on the oxidative metabolism of submerged cultures of Claviceps purpurea 129

In submerged cultures of Claviceps purpurea citrate utilization was stopped when the pool phosphate concentration decreased to 0.44–0.55 mmol per g of mycelial protein. The absence of citrate in the medium resulted in a 50% decrease of biomass, cessation of the alkaloid (agro-, elymo-, chanoclavine) synthesis, formation of a central large vacuole, cell enlargement and medium acidification by lactate. Citrate synthase and malate dehydrogenase gradually disappeared. Glucose-6-phosphate dehydrogenase was not detectable. The activities of glyceraldehyde-3-phosphate dehydrogenase and lactate dehydrogenase increased by one or two orders of magnitude higher than in control culture (with 80 mM citrate). Substrate competition on the pyruvate level is discussed.     

Menadione-resistant Chinese hamster cell variants are cross-resistant to hydrogen peroxide and exhibit stable chromosomal and biochemical alterations

We have investigated the antioxidant properties of V79 Chinese hamster cells rendered resistant to menadione by chronic exposure to increasing concentrations of this quinone. MD1, a clone of resistant cells, was compared to the parental M8 cells; the former showed increased activity of catalase (3 fold), glutathione peroxidase (1.6 fold) and DT-diaphorase (2.6 fold), as well as an increase in glutathione (3.2 fold). Although one of the products of menadione metabolism is superoxide anion, no changes in total superoxide dismutase activity was observed in MD1 cells. MD1 menadione resistant cells were also resistant to killing by hydrogen peroxide and contained tandem duplication of chromosome 6. A similar duplication of chromosome 6 was seen in several independently derived menadione resistant clones and therefore seems closed linked to the establishment of the resistance. Upon removal of menadione from the medium, some of these properties of MD1 cells, viz., resistance to menadione, elevated glutathione levels, and glutathione peroxidase activity, were lost and the cells resembled M8 cells. However, resistance to H₂O₂, elevated catalase activity and the duplicated chromosome remained stable for more than 40 cell passages in the absence of menadione. The increase in catalase activity was correlated with an increase in catalase mRNA content and a 50% amplification of catalase gene, as determined, respectively, by Northern and Southern blot analysis. The role of the chromosome 6 duplication in resistance to oxidative stress remains to be established. It is not responsible directly for elevated catalase levels since the catalase gene is on chromosome 3.Abbreviations SDS Sodium Dodecyl Sulphate - SOD Superoxide Dismutase - PBS Phosphate Buffered Saline (8.1 mM Na₂HPO₄, 1.47 mM KH₂PO₄, 2.68 mM KCl, 137 mM NaCl) - CDTA N,N,N,N-tetracetic-trans-1,2-diaminocyclohexane acid - MOPS Sulphonic-3-(N-morpholine)-propane acid - SSC 150 mM Nacl, 15 mM sodium-citrate, pH 6.8     

番禺市生态公益林林分改造与立法管理研究

针对番禺市森林资源偏少,林分质量欠佳的情况,近１０年来,对和天府以僧林林分改造和城市林业建设和管理进行不断的实践和探索。从番禺市生态公益林的基本情况和分布入手,总结了进行林改造的主要技术措施和行之有效的立法管理办法。     

Flow regulation increases food‐chain length through omnivory mechanisms in a Mediterranean river network

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Consequences of habitat disturbance on seed fate of a Brazilian tropical dry forest tree Cavanillesia arborea (Malvaceae)

We compared seed fate (survival, mortality by rodent predators, desiccation and other causes) of the tree Cavanillesia arborea (Malvaceae) in preserved old‐growth tropical dry forests and in nearby abandoned pasturelands in Brazil. For this purpose, we performed an experiment where 15 seeds were placed in the surroundings of 15 parental individuals in each habitat. These 450 seeds were monitored over four months. At the end of the experiment, seed predation by rodents was higher in forest (56.5%) than in pasture (8.9%) areas, but seed desiccation showed the opposite pattern (8.9% vs. 80.4%). Mortality by desiccation was also faster in pasture than in forest areas, probably reducing their attractiveness to predators in these areas. None of the seeds placed in the pasture survived, whereas 26.2% of seeds became seedlings in forest areas. The absence of seedling recruitment of Cavanillesia arborea in pastures is likely a consequence of their incapacity to tolerate the harsh abiotic conditions in this habitat. Thus, forest conversion imposes a strong limitation to the long‐term population viability of this species. However, restoration and natural regeneration of abandoned pastures can recreate the forest structure and microclimatic conditions favourable to seed germination and seedling establishment. Remnant individuals of Cavanillesia arborea in agricultural landscapes may have a negligible contribution to current recruitment, but they can attract potential dispersers of pioneer species, with positive feedbacks to future recruitment during secondary succession.