Genetic diversity,population structure,and historical demography of a highly vagile and human-impacted seabird in the Pacific Ocean: The red-tailed tropicbird,Phaethon rubricauda

1. Many seabird breeding colonies have recovered from heavy anthropogenic disturbance after conservation actions. The widely distributed red-tailed tropicbird, Phaethon rubricauda, was used as a model species to assess potential anthropogenic impacts on the genetic diversity of breeding colonies in the Pacific Ocean.
2. Cytochrome c oxidase subunit I and control region sequences analyses were conducted across the range of the species in the Pacific Ocean. The study sites were at islands without human-related disturbance (non-impacted islands) and with human-related disturbance (impacted islands). We hypothesized that (i) breeding colonies of the red-tailed tropicbird on impacted islands have lower genetic diversity compared with colonies on non-impacted islands, and (ii) breeding colonies of the red-tailed tropicbird show significant fine and broad-scale genetic structure across the Pacific Ocean. Bayesian skyline analyses were conducted to infer past changes in population sizes.
3. Genetic diversity was similar between impacted and non-impacted islands. There was significant broad-scale genetic structure among colonies separated by over 6,000 km, but a lack of significant fine-scale genetic structure within Australasia and Hawai'i, although a significant level of differentiation was found within Chile with Φ_ST analyses. Skyline analyses showed that effective population sizes remained relatively constant through time, but experienced either a slight decrease or the end of an expansion event through the last 1,000 years. These changes may be related to the arrival of humans on Pacific islands.
4. Impacted islands may have received immigrants from other relatively close islands, buffering the loss of genetic diversity. However, it is also possible that colonies have retained ancestral variation or that a large effective population size coupled with a long generation time (13 years) has prevented the loss of genetic diversity in human-impacted islands. Future research using higher-resolution markers is needed to resolve the population genetic structure of the red-tailed tropicbird in an ecological time-scale.

     

Daily variation in short-term static toxicity of unionized ammonia in Litopenaeus vannamei (Boone) postlarvae

Ammonium toxicity of short‐duration alkaline events and their variability, as related to 1–30 day‐old postlarvae whiteleg shrimp Litopenaeus vannamei (Boone), was assessed by determining medium lethal concentration (LC₅₀) of total ammonium‐nitroen (TAN) and NH₃‐N to 4‐h exposures. Exploratory concentrations of TAN were tested at 30°C and pH 9, until mortality from 5% to 95% occurred between 0.9 and 18 mg N L^?1. To determine the daily variation of ammonium toxicity, 64 lots of 20 postlarvae were exposed to eight different ammonium concentrations (0, 0.9, 3, 6, 9, 12, 15 and 18 mg N L^?1), in two different environmental scenarios: α (pH 8, 26°C) and β (pH 9, 30°C). In environmental scenario α, ammonium concentrations up to 18 mg L^?1 pose no short‐term mortality risks for ages 1–30 days. In scenario β, mortality was recorded at all ages. The values of LC₅₀ (4 h) for different postlarvae ages have daily variability, ranging from a minimum of 2.54 to a maximum of 6.02 mg L^?1 of TAN (0.76 and 1.81 mg N L^?1 of NH₃‐N), for PL₃ and PL₁₉, respectively, with a logarithmic linear tendency to increase with age. Postlarvae mortality at 4 h and 3.0 mg N L^?1 TAN exposure was lower and less variable in ages greater than 19 days old.     

Tillage systems for a cotton–peanut rotation with winter-annual grazing: Impacts on soil carbon, nitrogen and physical properties

Integrating livestock with cotton (Gossypium hirsutum L.) and peanut (Arachis hypogaea L.) production systems by grazing winter-annuals can offer additional income for producers provided it does not result in yield-limiting soil compaction. We conducted a 3-year field study on a Dothan loamy sand (fine-loamy, kaolinitic, thermic plinthic kandiudults) in southern Alabama, USA to determine the influence of tillage system prior to cotton–peanut planting on soil properties following winter-annual grazing. Two winter-annual forages [oat (Avena sativa L.) and annual ryegrass (Lolium mutiflorum L.)] and four tillage practices [chisel + disk, non-inversion deep tillage (paratill) with and without disking and no-till] were evaluated in a strip-plot design of four replications. We evaluated cone index, bulk density, infiltration, soil organic carbon (SOC), and total nitrogen (N). Paratilling prior to cotton or peanut planting, especially without surface soil tillage, reduced compaction initially to 40 cm and residually to 30 cm through the grazing period in winter. There were no significant differences in cone index, bulk density, or infiltration between forage species. No-tillage resulted in the greatest bulk density (1.65 Mg m⁻³) and lowest infiltration (36% of water applied), while paratilling increased infiltration in no-tillage to 83%. After 3 years, paratilling increased SOC 38% and N 56% near the soil surface (0–5 cm), as compared to concentrations at the beginning of the experiment, suggesting an improvement in soil quality. For coastal plain soils, integrating winter-annual grazing in a cotton–peanut rotation using a conservation tillage system of non-inversion deep tillage (paratill) with no surface tillage can improve soil quality by reducing cone index, increasing infiltration, and increasing SOC in the soil surface.     

Bioactive metabolites from the fungus Nectria galligena, the main apple canker agent in Chile

The phytopathogenic fungus Nectria galligena Bres. is the most common canker disease agent of hardwood trees. The terpenoids colletochlorin B, colletorin B, ilicicolin C, E, and F, as well as the phytotoxin alpha,beta-dehydrocurvularin have been isolated from liquid cultures of N. galligena obtained from the xylem of infected apple trees in central Chile. Ilicicolin C and F and alpha,beta-dehydrocurvularin were active against Pseudomonas syringae with IC50 values of 28.5, 28.5, and 14.2 microg/mL, respectively, in the same range as streptomycin and penicillin G (11 and 15 microg/mL, respectively). All of the compounds showed moderate inhibitory activity toward the enzymes acetylcholinesterase (AChE) and beta-glucuronidase. The most active enzyme inhibitors were colletochlorin B and ilicicolin C and E, with IC50 values of 30-36 microg/mL in the AChE assay and 32-43 microg/mL in the beta-glucuronidase test. All of the chlorinated compounds showed some toxicity toward human lung fibroblasts, with IC50 values in the range of 64-120 microg/mL. alpha,beta-Dehydrocurvularin proved to be the most toxic compound, showing IC50 values less than 12 microg/mL. The effect of the isolated compounds on seed germination and radicle and epicotyl growth was assessed in lettuce and millet seeds. At 100 and 200 microg/disk, alpha,beta-dehydrocurvularin significantly reduced radicle length and epicotyl growth in Lactuca sativa. This is the first report on the occurrence of colletochlorin B, colletorin B, ilicicolin C, E, and F, as well as alpha,beta-dehydrocurvularin associated to N. galligena.     

Free radical scavengers and antioxidants from Lemongrass (Cymbopogon citratus (DC.) Stapf.)

Methanol, MeOH/water extracts, infusion, and decoction of Cymbopogon citratus were assessed for free radical scavenging effects measured by the bleaching of the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical, scavenging of the superoxide anion, and inhibition of the enzyme xanthine oxidase (XO) and lipid peroxidation in human erythrocytes. The extracts presented effect in the DPPH and superoxide anion assay, with values ranging between 40 and 68% and 15-32% at 33 and 50 microg/mL, respectively, inhibited lipid peroxidation in erythrocytes by 19-71% at 500 microg/mL and were inactive toward the XO at 50 microg/mL. Isoorientin, isoscoparin, swertiajaponin, isoorientin 2' '-O-rhamnoside, orientin, chlorogenic acid, and caffeic acid were isolated and identified by spectroscopic methods. Isoorientin and orientin presented similar activities toward the DPPH (IC(50): 9-10 microM) and inhibited lipid peroxidation by 70% at 100 microg/mL. Caffeic and chlorogenic acid were active superoxide anion scavengers with IC(50) values of 68.8 and 54.2 microM, respectively, and a strong effect toward DPPH. Caffeic acid inhibited lipid peroxidation by 85% at 100 microg/mL.     

The Faustmann model as a model for a forestry of prices

The relation between the Faustmann model and “a forestry of prices” as a concept of thought was examined. At first, the meaning of the Faustmann model in economic sciences is the explanation of allocation and distribution by prices. The rotation age determination plays a secondary role only. Secondly, “a forestry of prices” as an application of the “free to choose” way of thinking is explained. The concept allows us to understand how individuals of anonymous groups achieve forest sustainability and provide forest environmental goods. Thirdly, the relation between the Faustmann model and “a forestry of prices” is discussed. For this purpose, the Faustmann model is described as a scientific laboratory. It helps us to observe how equilibrium arises as a non-intended result of individual welfare maximization in anonymous interactions. And conversely with the help of “a forestry of prices”, we understand also that the individual maximization approach of the Faustmann model re-enacts the unintended interaction situations in anonymous group. With help of the Faustmann model, we can understand deep aspects of “a forestry of prices”. Vice versa, “a forestry of prices” shows the meaning of the formal solutions of the Faustmann model.     

Dynamics of transpiration, sap flow and use of stored water in tropical forest canopy trees

In large trees, the daily onset of transpiration causes water to be withdrawn from internal storage compartments, resulting in lags between changes in transpiration and sap flow at the base of the tree. We measured time courses of sap flow, hydraulic resistance, plant water potential and stomatal resistance in co-occurring tropical forest canopy trees with trunk diameters ranging from 0.34-0.98 m, to determine how total daily water use and daily reliance on stored water scaled with size. We also examined the effects of scale and tree hydraulic properties on apparent time constants for changes in transpiration and water flow in response to fluctuating environmental variables. Time constants for water movement were estimated from whole-tree hydraulic resistance (R) and capacitance (C) using an electric circuit analogy, and from rates of change in water movement through intact trees. Total daily water use and reliance on stored water were strongly correlated with trunk diameter, independent of species. Although total daily withdrawal of water from internal storage increased with tree size, its relative contribution to the daily water budget (approximately 10%) remained constant. Net withdrawal of water from storage ceased when upper branch water potential corresponded to the sapwood water potential (Psi(sw)) at which further withdrawal of water from sapwood would have caused Psi(sw) to decline precipitously. Stomatal coordination of vapor and liquid phase resistances played a key role in limiting stored water use to a nearly constant fraction of total daily water use. Time constants for changes in transpiration, estimated as the product of whole- tree R and C, were similar among individuals (~0.53 h), indicating that R and C co-varied with tree size in an inverse manner. Similarly, time constants estimated from rates of change in crown and basal sap flux were nearly identical among individuals and therefore independent of tree size and species.     

Kepler-16: a transiting circumbinary planet

We report the detection of a planet whose orbit surrounds a pair of low-mass stars. Data from the Kepler spacecraft reveal transits of the planet across both stars, in addition to the mutual eclipses of the stars, giving precise constraints on the absolute dimensions of all three bodies. The planet is comparable to Saturn in mass and size and is on a nearly circular 229-day orbit around its two parent stars. The eclipsing stars are 20 and 69% as massive as the Sun and have an eccentric 41-day orbit. The motions of all three bodies are confined to within 0.5° of a single plane, suggesting that the planet formed within a circumbinary disk.