Direct Interference on Competition in a Chemostat

Thispaperstudiestheglobaldynamicsofcompetitioninchemostatinwhichtwopopulationsofmicrooganismscompeteexploitativelyforasingle,essential,nonreproducing,growth-limitingsubstrateandthereisadirectinterferencebetweencompetitors.Inordertounderstandthedifferencesintheeffectsofintraspecificandinterspecificinterference,thebothcasesareconsideredrespectively.Keywords:##4Populationdynamicsecology;;chemostat;;competition;;interference;;interspecific;;intraspecific;;principalofcompetitiveexclusion     

Reproductive interference hampers species coexistence despite conspecific sperm precedence

Negative interspecific mating interactions, known as reproductive interference, can hamper species coexistence in a local patch and promote niche partitioning or geographical segregation of closely related species. Conspecific sperm precedence (CSP), which occurs when females that have mated with both conspecific and heterospecific males preferentially use conspecific sperm for fertilization, might contribute to species coexistence by mitigating the costs of interspecific mating and hybridization. We discussed whether two species exhibiting CSP can coexist in a local environment in the presence of reproductive interference. First, using a behaviorally explicit mathematical model, we demonstrated that two species characterized by negative mating interactions are unlikely to coexist because the costs of reproductive interference, such as loss of mating opportunity with conspecific partners, are inevitably incurred when individuals of both species are present. Second, we experimentally examined differences in mating activity and preference in two Harmonia ladybird species known to exhibit CSP. These behavioral differences may lead to local extinction of H. yedoensis because of reproductive interference by H. axyridis. This prediction is consistent with field observations that H. axyridis uses various food sources and habitats whereas H. yedoensis is confined to a less preferred prey item and a pine tree habitat. Finally, by a comparative approach, we observed that niche partitioning or parapatric distribution, but not sympatric coexistence in the same habitat, is maintained between species with CSP belonging to a wide range of taxa, including vertebrates and invertebrates living in aquatic or terrestrial environments. Taken together, it is possible that reproductive interference may destabilize local coexistence even in closely related species that exhibit CSP.     

耐盐性不同的小麦根和根茎结合部的拒Na~ 作用

NaCl处理引起小麦幼苗干重下降 ,盐敏感品种比耐盐品种下降幅度要大。盐敏感品种的拒Na 能力为 35 %左右 ,耐盐品种的拒Na 能力为 5 0 %～ 6 0 %左右 ,这表明耐盐品种的拒Na 能力远远大于盐敏感品种。不同耐盐性小麦的拒Na 部位不同 ,盐敏感品种的拒Na 部位主要在根茎结合部 ,而耐盐品种的拒Na 部位主要在根部     

The inheritance of salt exclusion in woody perennial fruit species

Citrus and grapevines are salt-sensitive perennial crops. Damage caused by salinity is due mostly to accumulation of excessive concentrations of salt (Na- and Cl ions) in shoot tissues. In both crops, however, some rootstock varieties can restrict the accumulation of salt in scion leaves and stems. Salt-excluding rootstocks, however, are often deficient with regard to other desirable characteristics and as such their use is limited. As a consequence, we have conducted a range of crosses within both crops to select new salt-excluding hybrids which may have potential as new rootstocks and also to investigate the inheritance of salt exclusion in these woody perennials.In citrus, both Cl-ion and Na-ion exclusion has been observed as a continuous character and progenies segregate widely for their ability to restrict the accumulation of these ions in shoot tissues. The ability to exclude Cl ions appears to be independent of the ability to exclude Na ions. Thus a good Cl-ion excluder is not necessarily a good Na-ion excluder and vice versa. It has been possible, however, to select new salt-excluding citrus hybrids which perform as well as and sometimes better than parent varieties when grafted with a common scion and grown in artificially salinised field plots.In grapevines, the research has concentrated on the ability for Cl-ion exclusion and depending on the Cl-ion-excluding parent chosen this is inherited as either a polygenic or monogenic trait. In crosses between Vitis champini (Cl-ion excluder) and Vitis vinifera (Cl-ion accumulator), the ability to restrict Cl-ion accumulation in shoot tissues segregates widely with some offspring transgressing the performance of either parent. In crosses and backcrosses involving V. berlandieri and V. vinifera, however, hybrids segregate as either Cl-ion excluders or accumulators suggesting the effect of a major dominant gene for Cl-ion exclusion from V. berlandieri. This was evident from both field and glasshouse experiments although possible modifying genes from V. vinifera may affect the expression of this gene under glasshouse conditions in some crosses.     

The true trigger of shame: social devaluation is sufficient,wrongdoing is unnecessary

What is the trigger of shame? The information threat theory holds that shame is an evolved adaptation that is designed to limit the likelihood and costs of others forming negative beliefs about the self. By contrast, attributional theories posit that concerns over others' evaluations are irrelevant to shame. Instead, shame is triggered when a person attributes a negative outcome to their self, rather than to a particular act or circumstance. We conduct a strong test of the information threat hypothesis. In Study 1, participants imagined taking an action that, though morally unimpeachable, could be interpreted unfavorably by others. As predicted by the information threat theory, shame increased with the publicity of this act. In Study 2, participants played a public good game and then learned that the other participants either chose to keep interacting with them (inclusion) or not (exclusion)—ostensibly because of their contributions, but in fact randomly determined by the experimenter. Exclusion increased shame. Under-contribution did not. In fact, even the highest contributors tended to feel shame when excluded. These findings strongly suggest that the true trigger of shame is the prospect or actuality of being devalued by others.     

Isolation and characterization of polymorphic microsatellite loci for parentage analysis in a rhacophorid tree frog (Chirixalus eiffingeri) with unusual parental care

Chirixalus eiffingeri is an arboreal breeding rhacophorid frog with unique parental care behaviours. We developed 11 polymorphic microsatellites as genetic makers for parentage analysis to resolve the ecology of parental care. The numbers of alleles per locus ranged from two to 17. The observed and expected heterozygosities averaged 0.433 and 0.656, respectively. Total exclusionary probability of these loci is 0.984 when no parental genotypes are known, and is 0.999 when one of the parental genotypes is known. The results indicate that the 11 markers should provide sufficient resolution for inferring genetic parentage in C. eiffingeri.     

Inclusion and exclusion criteria for malformations in newborn infants exposed to potential teratogens

BACKGROUND: The surveillance of newborn infants exposed to potential teratogens often relies on the findings in routine physicians' examinations to identify malformations. Exposed newborn infants can have a wide variety of physical features, including malformations, birth marks, positional deformities, and minor anomalies. The routine physician's findings are not standardized. Some physicians record a wide variety of physical features and others do not. The purpose of this study was to develop criteria and definitions for identifying malformations and for identifying the more common and less severe physical features that would be excluded as not being malformations. METHODS: The physical features recorded by the examining pediatricians were obtained from a review of the medical records of a consecutive sample of 1000 liveborn and stillborn infants and elective terminations for fetal anomalies. RESULTS: A malformation, defined as a structural abnormality with surgical, medical or cosmetic importance, was present in 18 (2.8%) of the infants; 222 other recorded features were identified and excluded: malformations attributed to dominant or recessive genes (4) or chromosome abnormalities (6), minor anomalies and normal variations (65), birth marks (110), positional deformities (6), prematurity‐related features (5), physiologic findings (4) and findings identified by prenatal ultrasound (but not by the examining pediatrician) (20), functional abnormalities (1) and findings in newborn screening (1). CONCLUSIONS: Investigators should establish, in advance, the exclusion criteria to be used in programs, such as malformation surveillance programs or pregnancy registries, whose findings are based on a review of the routine examinations in medical records. It is essential that the same criteria be used in evaluating the drug‐exposed and the unexposed comparison group. Birth Defects Research(Part A), 2011. © 2011 Wiley‐Liss, Inc.     

Ion Exclusion Chromatography: Parameters Influencing Retention

Ion Exclusion Chromatography (IEC) finds application in the separation of a wide range of small, neutral or partially ionized molecules. In IEC, the strong as well as weak electrolytes are eluted unseparated, the first at the beginning and the latter at the end of the elution. The retention volumes of the remaining electrolytes are found to be proportional to their dissociation constant values. The dead and inner volumes of the chromatographic column can be determined from the observed dependence of retention volumes on dissociation constant values. The retention mechanism is described by the analytical equations and by the results obtained from the computer simulation of the column performance (using global thermodynamic and chromatographic equations or the Craig method). The mixed retention mechanism involving hydrophobic adsorption and screening effect is observed for weak electrolytes and aromatic compounds. Aromatic compounds are found to be retained almost solely by a reverse-phase mechanism involving interaction of the solute with the unfunctionalized regions of the stationary phase. The purpose of this paper is to survey the field. Using theoretical and experimental approaches, I show how different parameters can influence ion-exclusion solute retention. Although this retention is affected by the physicochemical parameters of the sorbent, stationary and mobile phases especially, this study primarily deals with the structural solute parameters, stationary phase form and column temperature, that have had little or no discussion in literature.     

Competitive exclusion and coexistence for pathogens in an epidemic model with variable population size

We study an SIR epidemic model with a variable host population size. We prove that if the model parameters satisfy certain inequalities then competition between n pathogens for a single host leads to exclusion of all pathogens except the one with the largest basic reproduction number. It is shown that a knowledge of the basic reproduction numbers is necessary but not sufficient for determining competitive exclusion. Numerical results illustrate that these inequalities are sufficient but not necessary for competitive exclusion to occur. In addition, an example is given which shows that if such inequalities are not satisfied then coexistence may occur.     

An evaluation of allowing for mismatches as a way to manage genotyping errors in parentage assignment by exclusion

In parentage assignment by exclusion, using multiple and very polymorphic loci, genotyping errors are a major cause of non‐assignment. Using stochastic simulations, we tested the possibility to allow for mismatches at one or more allele as a way to recover assignment power. This was very efficient provided the set of loci used had a high assignment power (> 99%) and the error rate was not too high (below 3–4%). In these cases, most of the theoretical assignment power could be recovered. We also showed the efficiency of the method in a practical experiment with rainbow trout.     

Development of coencapsulating technology for the production of chitosanoligosaccharides

To easily separate chitosanoligosaccharides by size exclusion, an coencapsulating technology of substrate and enzyme was developed. The membrane was composed of alginate and a divalent cation such as calcium. Chitosan and chitosanase were enveloped in this membrane and the product released to medium by size exclusion. The capsule was stabilized in a 2% acetic acid solution (pH 5.0) containing 0.145 M CaCO₃. The leakage of substrate caused by the agitation speed was controlled by increasing alginate and CaCO₃ concentrations. The lower limit of the alginate concentration and the agitation speed were 0.5% and 40 rpm, respectively. Membrane thickness and capsule diameter were 10 μm and 2.5 mm, respectively. By TLC analysis, the composition of chitosanoligosaccharides were mainly 3–6 mers. The molecular weight distribution of the released oligosaccharides ranged from 262 to 3624 Da by GPC.     

Why only one of two common Central Texas Anostraca atop Enchanted Rock?

Branchinecta packardi Pearse, 1912 grows rapidly and begins reproducing at the age of seven days. The first clutch contains only one or two eggs. Females deposit a clutch each day. Reproductive populations occur during all seasons in Central Texas. Streptocephalus texanus Packard, 1871 has a slower growth rate and does not begin reproduction until 11 days of age. Females deposit a clutch every second day. The species is a warm season form in Central Texas. These life history differences most likely explain why B. packardi inhabits the shallow, exposed weather-pit pools atop Enchanted Rock and S. texanus does not.     

Impacts of ambient solar uv (280-400 nm) radiation on three tropical legumes

Tropical regions receive the highest level of global solar ultraviolet (UV) radiation especially UV-B (280-320 nm). The average daily dose of the UV-B radiation in Madurai, South India (10°N) is 10 kJ m^-2. This is approximately 50% more than the average daily UV-B radiation in many European countries. A field study was conducted using selective filters to remove either the UV-B (< 320 nm) or UV-B/A (<400 nm) of the solar spectrum, and the effects were followed inCyamopsis tetragonoloba, Vigna mungo, andVigna radiata to determine their sensitivity to UV. When compared to ambient radiation, exclusion of solar UV-B increased the seedling height, leaf area, fresh weight and dry weight and the crop yield by 50% in the case ofCyamopsis, and the extent of such increase was slightly less under UV-B/A exclusion. InV. mungo a significant reduction was seen in solar UV excluded plants whileV. radiata was found to be unaffected.     

Charaterization and hydrodynamic behaviour of modified gelatin: II. Characterization by high performance size exclusion chromatography — comparison with dextrans and proteins

Gelatin samples obtained by chemical modification (succinylation) are studied by SEC on silica based chromatographic supports. The influence of the pH of eluent mixtures (potassium phosphate added to NaCl) in the range 7-3.3 shows that the void volume peak (VVP) is lowered or even vanishes at pH 3.3 with the 3000 SW (TSK) gel. A process using an ultrasound treatment before injection is reported in order to determine accurately the molecular parameters of gelatin onto TSK gel with a minimal VV P. This peak is attributed to molecular aggregation of a part of the modified gelatin. After disaggregation by ultrasound or heat treatment the results are in good accordance with those obtained by other methods. It is demonstrated that with proteins and dextrans the TSK 3000 SW gel does not agree with the universal calibration curve (log[ν] · versus K_d as reported previously. A single calibration curve is obtained when the Stokes radius is plotted versus K_d. Gelatin fractions are eluted at pH 7 close to this calibration curve. This plot shows that gelatin fractions at pH 3.3 are not eluted by a pure size exclusion mechanism on 3000 SW gel. It is concluded that hydrophobic interactions between fractions of gelatin and the gel explain the high retention of these samples.     

体积排阻液相色谱法质粒的含量测定

首次以体积排阻液相色谱法进行质粒提取液浓度的测定研究,通过纯质粒溶液在260 nm处的紫外吸峰面积与质粒浓度之间数据的线性最小二乘拟合,得到了反映质粒浓度和紫外吸收峰峰面积之间关系的标准曲线:Y=2×10~(-5) X,通过验证实验,确定了质粒提取液中不同组分,如核糖核酸,蛋白质等在色谱图中的出峰位置.结合标准曲线测定了自制的质粒提取液的质粒浓度为0.32 mg/mL.该方法方便,快捷,准确.     

Insect natural history,multi-species interactions and biodiversity in ecosystems

The composition and dynamics of ecosystems are influenced by insects serving as providers, eliminators and facilitators across multiple trophic levels. The role of insects in ecosystems may be documented by manipulative field studies involving exclusion techniques applied to species that are decomposers, herbivores or predators. The presence or absence of insects is important to the distribution, abundance and diversity of plants and vertebrates, which typically are the premier species in conservation efforts. Thus, policy-making in environmental management programmes should consider the role of insects in ecosystems when establishing objectives and procedures for species conservation and biodiversity.     

RNA干扰技术治疗疾病

RNA干扰(RNA interference,RNAi)现象最早发现于秀丽隐杆线虫(Caenorhabditis elegans),随后发现该现象普遍存在于真菌、植物和哺乳动物等真核生物,并行使基因调控和抵御外源基因片段侵袭的作用。目前,RNAi分子机制和RNAi在基因功能方面的研究已经取得了突破性的进展。鉴于RNAi在基因沉默中的特异性、高效性和易操作,其在药物筛选和疾病治疗等方面有着广泛的应用前景。然而,RNAi技术用于治疗疾病的安全性尚待确定,分子传递途径也有待进一步的研究。     

A cytogenetic study of development in mechanically disrupted pairs of Tetrahymena thermophila

We examined the nuclear behavior of mating Tetrahymena cells that had been mechanically disrupted at various times throughout conjugation. Disruption was achieved by agitating conjugating Tetrahymena in the presence of 0.1-3 mm glass beads. Two minutes of agitation with 1 mm beads yielded optimal pair disruption (70%) with high viability (92%). Disrupting pairs between 0-4.7 h after the initiation of mating produced mostly disrupted conjugants in which development was aborted. However, as many as 20% of these early disrupted conjugants completed development even without their mating partners. After 5 h the percentage of disrupted conjugants completing development increased dramatically, reaching 80% by 6.7 h. These results support a model suggesting that events associated with nuclear exchange and fusion 5 h into conjugation trigger a commitment to completion of the postzygotic developmental program. The early conjugants that completed development following disruption suggest that development can be sustained even in the absence of a mating partner. This represents a novel method of bringing the micronuclear genome into macronuclear expression with minimal cytoplasmic exchange between partners. We discuss these results in light of a model relating cortical and nuclear signaling events that reciprocally drive conjugal development.     

DNA “fingerprints” and paternity ascertainment in chimpanzees (Pan troglodytes)

Highly variable regions of DNA are found in a wide diversity of organisms and are typically composed of alleles consisting of a variable number of tandem repeats (VNTRs) of a short core sequence. DNA fingerprinting probes are VNTR probes that simultaneously detect a large number of similar VNTRs in the target DNA. The highly polymorphic pattern observed in a DNA fingerprint allows resolution of questions concerning individual identification. M13 phage was used to fingerprint captive chimpanzees for paternity ascertainment. Although the probability of band sharing among captive chimps appears to be higher than among some other reported captive and feral animal populations, the probe is highly useful and can be expected to become more widely used in the genetic management of captive populations.     

Experimental field exclosure of birds and bats in agricultural systems — Methodological insights,potential improvements,and cost-benefit trade-offs

Experimental exclosure of birds and bats constitutes a powerful tool to study the impacts of wildlife on pests and crop yields in agricultural systems. Though widely utilized, exclosure experiments are not standardized across studies. Indeed, key differences surrounding the design, materials, and protocols for implementing field-based exclosure experiments of flying vertebrates increase heterogeneity across studies, and limit our understanding of biodiversity-friendly land use management. We reviewed the available literature on studies in which bird and bat exclosures were applied to study pest control in agricultural settings, and isolated 30 studies from both tropical and temperate land use systems, involving 12 crop types across 14 countries. Focusing on exclosure effects on crop yield, we analyzed effect detectability for a subset of suitable data. We then analyzed the potential of exclosure methods and possible extensions to improve our understanding of complex food webs and ecosystem services affecting the productivity of agricultural systems. While preferences exist in materials (e.g., nylon nets and bamboo frames), experimental exclosure studies of birds and bats differed greatly in their respective design, related costs, and effort — limiting the generalization and transferability of results at larger spatial scales. Most studies were based on experiments conducted in the United States and the Neotropics, mainly in coffee and cacao farms. A lack of preliminary or long-term data with repeated measurements makes it impossible to apply power analysis in most studies. Common constraints include, among other things, the choice of material and experimental duration, as well as the consideration of local versus landscape factors. We discuss such limitations, related common pitfalls, and options for optimization to inform improved planning, design, and execution of exclosure studies. By doing so, we aim to promote more comparable and transferable approaches in future field research on biodiversity-mediated ecosystem services.