Hierarchical Bayesian modeling in dichotomous processes in the presence of nonresponse

Sampling units that do not answer a survey may dramatically affect the estimation results of interest. The response may even be conditional on the outcome of interest in the survey. If estimates are found using only those who responded, the estimate may be biased, known as nonresponse bias. We are interested in finding estimates of success rates from a survey. We begin by looking at two current Bayesian approaches to treating nonresponse in a hierarchical model. However, these approaches do not consider possible spatial correlations between domains for either success rate or response rate. We build a Bayesian hierarchical spatial model to explicitly estimate the success rate, response rate given success, and response rate given failure. The success rates in the domains of the survey are allowed to be spatially correlated. We also allow spatial dependence between domains in both response rate given success and response rate given failure. Spatial dependence is induced by a common latent spatial structure between the two conditional response rates. We use the 1998 Missouri Turkey Hunting Survey to illustrate this methodology. We find significant spatial correlation in the success rates and incorporating nonrespondents has an impact on the success rate estimates.     

Changes in postsynaptic excitation processes in the presence of phenazepam]

The new psychotropic drug phenazepam inhibits the impulse activity of the neurons which compose visceral ganglia of the garden snail (Helix aspersa) and suppresses stimulating postsynaptic potentials arising in application of acetylcholine to the membrane of isolated neurons. The electrostimulating membrane parameters are not generally changed. Postsynaptic depression of the stimulation of the cholinoreceptive membrane is suggested to be one of the possible mechanisms of the pharmacological action of the drug.     

Reduced dietary conservatism in a wild bird in the presence of intraspecific competition

The presence of intraspecific competitors can increase foraging costs through exploitation of resources. Optimal foraging theory suggests that when the cost of pursuing one food type increases, alternative resources should be accepted. Accepting novel foods readily might put a competitor at an advantage over its more conservative rivals in the race for sufficient sustenance, but also opens it to the danger of poisoning by chemically protected food. Dietary conservatism is a foraging behaviour characterised by a prolonged avoidance of novel foods, long after neophobia (initial fear of novel objects) has been overcome, and so might be seen as a disadvantage to foragers in a competitive situation. There are two stable foraging strategies found within forager populations: 1) adventurous consumers (AC) which rapidly accept novel foods and 2) foragers showing dietary conservatism (DC). The expression of these two strategies may also vary with environmental conditions. The aim of this study was to investigate the effect of intraspecific competition on the levels of dietary conservatism displayed among wild caught blue tits Cyanistes caeruleus. Blue tits were offered items of both novel and familiar foods under two conditions: with a competitor and without. Our results showed that individuals who experienced competition incorporated the novel items into their diet faster than those who did not experience competition. This study demonstrates, for the first time, the degree of plasticity in the expression of the DC trait using wild birds in laboratory conditions. This plasticity represents a significant adaptation to reduce the costs of foraging conservatively when novel alternative resources should be accepted.     

Assessing the outcomes of stocking hatchery-reared juveniles in the presence of wild Atlantic salmon

Stocking of hatchery-reared juvenile Atlantic Salmon Salmo salar is a common enhancement and recovery strategy across jurisdictions, yet its impact remains uncertain. We investigate the potential effectiveness of stocking in the Miramichi River system where approximately 150,000 first-feeding fry are stocked annually in reaches where wild juveniles are present. Local site and landscape level characteristics were used to fit predictive models for wild parr densities measured as Percent Habitat Saturation (PHS) using Partial Least Squares Regression (PLSR). The observed PHS of stocked sites was found to be significantly lower than predicted, suggesting stocking has not been effective in increasing the PHS in the studied stocked sites. The results suggest that habitat and other density dependent effects limit productive capacity in this system, and consequently, may limit the effectiveness of stocking in other systems with natural production.     

Urinary testosterone levels of wild male bonobos (Pan paniscus) in the Lomako Forest, Democratic Republic of Congo

We collected urine samples from seven male bonobos (Pan paniscus) in the Eyengo community, Lomako Forest, Democratic Republic of Congo, and assayed them for testosterone (T). T levels averaged 525 pmol/mg Cr in adult males, and 309 pmol/mg Cr in subadult males. We collected hormonal and behavioral data during a period of relative social instability following the recent arrival of two immigrant males. In concordance with predictions derived from the challenge hypothesis [Wingfield et al., American Naturalist 136:829-846, 1990], which relates T to levels of reproductive aggression, the alpha male had the highest circulating levels of T. When we removed the two recent immigrant males from the analysis, there was a significant positive correlation between T levels and dominance rank for the long-term resident males (n=5, P=0.001, r2=0.98). These are the first data on T levels in wild bonobos, and the results suggest that further study of the relationship between T levels and social context in this species could inform current models relating hormones and aggression in wild apes.     

The concrete evidence of flexistyly in Plagiostachys: pollination biology of a wild ginger on Hainan Island,China

Flexistyly in Plagiostachys was first reported by Takano et al., while they provided no detailed study on pollination biology and breeding system. In this study, we tested this suspicion in one species of Plagiostachys (Plagiostachys austrosinensis). Field observations suggested that flexistyly was present in this species, and stigmatic behavior was similar to that reported for Alpinia and Amomum species. Two phenotypes (anaflexistylous and cataflexistylous) occurred in a ratio of 1:1 in natural populations. Anthesis began around 1530–1600 h and lasted for about 24 h. Pollen viability and stigma receptivity remained high throughout the flowering process. Mean nectar volume (4.15–11.30 μL) and mean sugar concentration (>32%) also remained at a high level during the flowering process. No fruit set occurred in unpollinated bagged plants. Two pollinators (Bombus pyrosoma and Vespidae spp.) and one pollen robber (Mutillidae spp.) were found as flower visitors. Fruit set following self‐pollination and cross‐pollination did not differ significantly in the cataflexistylous morph. Partial self‐incompatibility was apparent in the anaflexistylous morph. These results provide the concrete evidence of flexistyly in Plagiostachys and a more thorough understanding of its evolutionary origin in gingers.     

Results of two-year-old inspection of the presence of infuenza virus in wild birds in Western Mongolia

The results of virology inspection of the wild birds living in territory of the Western Mongolia, carried out in 2003-2004 are presented. For the specified period influenza viruses H3 and H4 subtype hemagglutinins are isolated from birds. It is revealed taxonomic and ecological heterogeneity of the birds involved in maintenance of circulation of influenza viruses in the given territory. Influenza viruses are isolated from birds of 5 special groups; among them there are preferring water and nearwater biotops, a species preferring dry plain region, and also a species which habitat does not depend from water's territories.     

A framework for comparing processes of speciation in the presence of gene flow

How common is speciation‐with‐gene‐flow? How much does gene flow impact on speciation? To answer questions like these requires understanding of the common obstacles to evolving reproductive isolation in the face of gene flow and the factors that favour this crucial step. We provide a common framework for the ways in which gene flow opposes speciation and the potential conditions that may ease divergence. This framework is centred on the challenge shared by most scenarios of speciation‐with‐gene‐flow, i.e. the need for coupling among different components of reproductive isolation. Using this structure, we review and compare the factors favouring speciation with the intention of providing a more integrated picture of speciation‐with‐gene‐flow.     

Nitrogen nutrition of ginger (Zingiber officinale)

Summary Two fertilizer experiments were conducted in the field at Beerwah, South-East Queensland. In the first experiment leaf nitrogen concentrations, and the yield of ginger shoots and rhizomes at early and late harvests increased both with the total amount of nitrogen applied up to the highest level studied (336 kg N/ha as ammonium nitrate) and with the number of applications making up the total. At all levels of nitrogen application the apparent recovery of fertilizer nitrogen increased in the order 1 application <2 applications <4 applications. At 33.6 kg N/ha there appeared to be no advantage in dividing the total N applied into more than 4 applications but the data suggested higher recoveries of nitrogen with 8 applications at 112 kg N/ha and 336 kg N/ha. In the second experiment, ammonium nitrate, urea, and ammonium sulphate were found to be equally effective as nitrogen fertilizers for ginger when applied at equal rates of nitrogen per hectare. However, in terms of cost effectiveness they rated in the order urea > ammonium nitrate > ammonium sulphate.All three nitrogen sources acidified the soil, the decrease in soil pH during the growing season increasing with increasing rate of application. In Experiment 1 split applications, which increased the recovery of applied nitrogen in the crop, also increased the extent of acidification. In Experiment 2 ammonium sulphate tended to be more strongly acidifying than the other fertilizers but the difference was statistically significant only at the highest rate of nitrogen application. Because of the strong effects of nitrogen supply on both yield and soil pH, the highest yields were associated with end-of-season pH values below 5.0.     

Feeding and foraging of wild and sterile Mediterranean fruit flies (Diptera: Tephritidae) in the presence of spinosad bait

The sterile insect technique (SIT) is used to control wild Mediterranean fruit fly introductions in California and Florida in the U.S. In the past, bait sprays containing malathion proved invaluable in treating new outbreaks or large populations before the use of SIT. Recently, a spinosad protein bait spray, GF-120, has been developed as a possible alternative to malathion, the standard insecticide in protein bait sprays. In this study, protein-deficient and protein-fed Vienna-7 (sterile, mass-reared, "male-only" strain) flies and wild males and females were evaluated to determine the effectiveness of the GF-120 protein bait containing spinosad with respect to bait attraction, feeding, and toxicology. There were no effects of diet or fly type on feeding duration in small laboratory cages. Wild flies, however, registered more feeding events than Vienna-7 males. Flies that fed longer on fresh bait died faster. Protein-deficient flies were more active and found the bait more often than protein-fed flies. Data suggest that adding protein to the diet of SIT flies may decrease their response to baits, therefore, reduce mortality, and thus, allow the concurrent use of SIT and bait sprays in a management or eradication program.     

Thermal degradation processes of end-capped poly(L-lactide)s in the presence and absence of residual zinc catalyst

Thermal degradation processes of end-capped poly(L-lactide)s (PLLAs) were investigated by means of several thermoanalytical techniques under both isothermal and nonisothermal conditions. Based on the thermogravimetric analysis, it was found that two distinct processes at temperatures below and above 330 degrees C were existed in the nonisothermal degradation for PLLA samples depending on the amounts of residual zinc compounds from synthesis process. Isothermal degradation experiments at different temperature regions showed that the sample weight of PLLA decreased linearly with time in both cases, whereas the changes in molecular weight revealed different tendency for the temperature. On the basis of characterization of the residual PLLA molecules after isothermal degradation at 330 degrees C, it was confirmed that the omega chain end of the residual molecules was an acrylic ester unit. Majority of volatile products during thermal degradation of PLLA was the lactide regardless of the degradation temperature. From these results, it is concluded that, during the thermal degradation of PLLA samples in the presence of large amounts of residual zinc compounds, the zinc compounds catalyze both the intermolecular transesterification generating PLLA with low molecular weights and the selective unzipping depolymerization of PLLA with low molecular weights at temperatures below 330 degrees C. In contrast, the primary reaction of thermal degradation for PLLA in the absence of residual zinc compounds above 330 degrees C is a competition between the random chain scission via a cis-elimination reaction and the cyclic rupture via intramolecular transesterification of PLLA molecules. In addition, it was evidenced that the racemization of lactic acid units in the main chain of PLLA molecules occurred at temperatures above 330 degrees C.     

Genetic variability in wild cherry populations in France. Effects of colonizing processes

 Isoenzymes were used to evaluate gene diversity and genetic differentiation among six populations of wild cherry (Prunus avium L.) in France. We contrast the genetic characteristics of a population resulting from a recent colonization with those of a much older population of the same species. No significant genetic structure was observed among populations; in this respect wild cherry does not differ from other forest trees. No founder effects could be detected in the newly colonized population. To explain the results, we discuss classic explanations for the lack of genetic differentiation among populations, including balancing selection and neutral drift/migration. In order to account for the absence of founder effects, we propose a hypothesis based on the life cycle of forest trees, namely that the length of the juvenile phase reduces the impact of small numbers of initial founders. Received : 26 November 1996 / Accepted : 20 December 1996     

Electrical relaxation processes in black lipid membranes in the presence of a cation-selective ionophore

Summary The time course of relaxation of the electric current following steps in the applied potential across lipid bilayer membranes has been measured. The membranes were made cation-selective by the addition of nonactin. To permit the measurement of very short time constants a voltage clamp device was developed in order to reduce the charging period to less than 1 sec, regardless of the magnitude of the series resistances in the external solutions. It was possible by this method to establish the presence of two electric processes, which were found to behave differently with respect to temperature, applied potential and external solution conditions. The rapid process (10 sec) was interpreted in terms of the electric parameters of the polar part of the membrane according to the theory developed by Hägglund and Sandblom (T.I.T.J. Life Sci. 2: 107, 1972). The second process (100 sec) showed a behavior consistent with the model of Stark, Ketterer, Benz and Läuger (Biophys. J. 11:981, 1971), which considers the different rate constants involved in the net transfer of carriermediated ion transport across bilayer membranes.     

Sodalis glossinidius presence in wild tsetse is only associated with presence of trypanosomes in complex interactions with other tsetse-specific factors

Background

Susceptibility of tsetse flies (Glossina spp.) to trypanosomes of both humans and animals has been associated with the presence of the endosymbiont Sodalis glossinidius. However, intrinsic biological characteristics of the flies and environmental factors can influence the presence of both S. glossinidius and the parasites. It thus remains unclear whether it is the S. glossinidius or other attributes of the flies that explains the apparent association. The objective of this study was to test whether the presence of Trypanosoma vivax, T. congolense and T. brucei are related to the presence of S. glossinidius in tsetse flies when other factors are accounted for: geographic location, species of Glossina, sex or age of the host flies.

Results

Flies (n = 1090) were trapped from four sites in the Shimba Hills and Nguruman regions in Kenya. Sex and species of tsetse (G. austeni, G. brevipalpis, G. longipennis and G. pallidipes) were determined based on external morphological characters and age was estimated by a wing fray score method. The presence of trypanosomes and S. glossinidius was detected using PCR targeting the internal transcribed spacer region 1 and the haemolysin gene, respectively. Sequencing was used to confirm species identification. Generalised Linear Models (GLMs) and Multiple Correspondence Analysis (MCA) were applied to investigate multivariable associations. The overall prevalence of trypanosomes was 42.1%, but GLMs revealed complex patterns of associations: the presence of S. glossinidius was associated with trypanosome presence but only in interactions with other factors and only in some species of trypanosomes. The strongest association was found for T. congolense, and no association was found for T. vivax. The MCA also suggested only a weak association between the presence of trypanosomes and S. glossinidius. Trypanosome-positive status showed strong associations with sex and age while S. glossinidius-positive status showed a strong association with geographic location and species of fly.

Conclusions

We suggest that previous conclusions about the presence of endosymbionts increasing probability of trypanosome presence in tsetse flies may have been confounded by other factors, such as community composition of the tsetse flies and the specific trypanosomes found in different regions.

     

Forest association and phenology of wild coffee in Kibale National Park, Uganda

A study on the forest association and phenology of wild coffee ( Coffea canephora Pierre) was conducted in Kibale forest, Uganda. Nested quadrats were used to enumerate tree species, including coffee and herbaceous plants associated with forest and coffee stands. A total of 150 coffee trees was marked along transects and monthly scans carried out to score for fruits, flowers, leaves and leaf insect damage. Pre- and post-dispersal predation levels and coffee yield estimates were made by examining fruits from trees, forest floor and seasonal fruit falls into demarcated plots. In the forest, wild coffee stands are associated with low-quality forest types in terms of timber species (about 10.5 canopy species/study site) and low stocking densities of trees ≥ 50 cm d.b.h. (average 38 trees ha⁻¹ for each site) and poor forest regeneration. In the forest, wild coffee reproductive phases overlap with ripening, coinciding with flower bud and flower production. The variable peak ripening season falls between November and April. The wild coffee yields are generally low (average of 3.5 intact fruits 16 m⁻² month⁻¹), with low insect fruit/seed damage (4–19%) but high levels of wastage due to monkeys, bats and birds.     

Tool-set for termite-fishing and honey extraction by wild chimpanzees in the Lossi Forest, Congo

The use of perforating sticks and flexible stalks in combination for termite fishing and a complex tool-set of three components used sequentially (stout chiel, bodkin, and dip-stick) to penetrate melipone and ground-dwelling bee hives byPan troglodytes troglodytes are documented or, inferred from circumstantial evidence. Functionally, termite extraction tools were similar to other locations in west and central Africa, but the plants and the number of raw material species used were different. Tools varied in the degree of modification (fraying ends). Chimpanzees in the Lossi forest seem to be able to use the tools not in a stereotyped fashion, but in a flexible, insightful way. The extraction of Melipone honey using large pieces of wood as pounding tools has rarely been recorded elsewhere. The most impressive technological solution to the honey-getting problem by wild chimpanzees was shown by this study. This is the only known, use of a tool-set of three components in sequence to extract honey by wild chimpanzees.     

Thermodynamic and kinetic processes during the unfolding of BSA in the presence of the mycotoxin patulin

The effects of the mycotoxin patulin on the thermodynamics and kinetics of the transition of bovine serum albumin (BSA) in aqueous solution were studied by Differential Scanning Calorimetry and Photoluminescence methods. Results show that in the presence of patulin, the free enthalpy change during the transition of BSA was decreased by an average of ～ 46 kJ/mol, the free energy change was decreased by ～ 4 kJ/mol, and the activation energy fell from ～ 1546 to ～ 840 kJ/mol. These results indicate that the bioactivity of patulin is based on the kinetic rather than on the thermodynamic properties of the transition. This is the first evidence of the direct interaction of patulin with the free thiol-containing BSA, a process which could contribute to the adverse cyto- and genotoxic effects induced by patulin.     

Soil processes and sulfate loss at the Hubbard Brook Experimental Forest

The Hubbard Brook Ecosystem Study was designed to evaluate element flux and cycling in a northern hardwood forest and the effects of disturbance on these processes. In the original experiment, an entire watershed was deforested and regrowth was inhibited for three years using herbicides. Initial effects of the treatment included: elevated stream discharge, large increases in streamwater solute concentrations and elevated losses of those ions from the watershed. In contrast, streamwater concentrations and net ecosystem output of sulfate decreased in response to the treatment. During the post treatment period, the concentrations of most dissolved ions declined relative to a reference watershed while, again in contrast, sulfate concentrations increased relative to the reference. In this paper we develop a hypothesis which links acidification and sulfate adsorption processes in the soil to explain the observed trends in sulfate losses from the Hubbard Brook Experimental Forest.