Understanding how population sizes vary over time is a key aspect of ecological research. Unfortunately, our under- standing of population dynamics has historically been based on an assumption that individuals are ide...Understanding how population sizes vary over time is a key aspect of ecological research. Unfortunately, our under- standing of population dynamics has historically been based on an assumption that individuals are identical with homogenous life-history properties. This assumption is certainly false for most natural systems, raising the question of what role individual variation plays in the dynamics of populations. While there has been an increase of interest regarding the effects of within popula- tion variation on the dynamics of single populations, there has been little study of the effects of differences in within population variation on patterns observed across populations. We found that life-history differences （clutch size） among individuals ex- plained the majority of the variation observed in the degree to which population sizes of eastern fence lizards Sceloporus undula- tus fluctuated. This finding suggests that differences across populations cannot be understood without an examination of differences at the level of a system rather than at the level of the individual展开更多
The aim of this research was to evaluate the salinity tolerance in prairie grass populations at the seedling stage quantifying the variability and the influence of physiological traits related to it. Salinity toleranc...The aim of this research was to evaluate the salinity tolerance in prairie grass populations at the seedling stage quantifying the variability and the influence of physiological traits related to it. Salinity tolerance, in </span><i><span style="font-family:Verdana;">Bromus</span></i> <i><span style="font-family:Verdana;">catharticus</span></i><span style="font-family:Verdana;"> Vahl (prairie grass) populations collected in different environments of the Pampean Phytogeography region (Argentine) was evaluated at the seedling stage, using controlled condition of temperature and light. It was adopted a completely randomized design using 3 plots with three plants each one per population and two levels of treatment: 0 mM and 100 mM NaCl. Morphological, biomass and membrane stability root and shoot traits were studied. A factorial ANOVA with interaction was estimated. Then one way ANOVA for all seedling traits in both treatments allowed estimating variance components, coefficient of genotypic determination (CGD) and variation index (VI). Comparisons between populations were made using Tukey test (at 5% of probability). Phenotypic correlations among traits were calculated and then a path coefficient analysis separated direct and indirect effects at 100 and 0 mM NaCl. No significant interactions “Population × Treatment” were found for any character. The saline stress caused a pairing in the population means for the most traits. Coefficients of variation were mainly higher when the seedlings grew without stress (0 mM) because it allowed a greater potential genotypic expression. The absence of significant interactions denotes a good homeostatic capacity of the prairie grass facing that abiotic stress. Leaf length, shoot length and root dry matter were the variables with the largest direct and indirect effects. Our results showed an increase for them at salt and demonstrated intraspecific variation, possibly in relation with the origin sites. Plants under stress showed a marked resilience, in order to quickly restore the same biomass allocation patterns that occur in non-stress environment.展开更多
A new idea on how to conceptually interpret the so-called Taylor’s power law for ecological communities is presented. The core of our approach is based on nonextensive/nonlinear statistical concepts, which are shown ...A new idea on how to conceptually interpret the so-called Taylor’s power law for ecological communities is presented. The core of our approach is based on nonextensive/nonlinear statistical concepts, which are shown to be at the genesis of all power laws, particularly when a system is constituted by long-range interacting elements. In this context, the ubiquity of the Taylor’s power law is discussed and addressed by showing that long-range interactions are at the heart of the internal dynamics of populations.展开更多
Hypericum perforatum is a perennial medicinal plant known as ＂St. John＇s wort＂ in Western Europe and has been used in the treatment of several diseases for centuries. In the present study, morphologic, phenologic a...Hypericum perforatum is a perennial medicinal plant known as ＂St. John＇s wort＂ in Western Europe and has been used in the treatment of several diseases for centuries. In the present study, morphologic, phenologic and population variability in pseudohypericin and hyperforin concentrations among H. perforatum populations from Northern Turkey was investigated for the first time. The aerial parts of H. perforatum plants representing a total of 30 individuals were collected at full flowering from 10 sites of Northern Turkey to search the regional variation in the secondary metabolite concentrations. For morphologic and phenologic sampling, plants from one site were gathered in five phenological stages： vegetative, floral budding, full flowering, fresh fruiting and mature fruiting. The plant materials were air-dried at room temperature and subsequently assayed for chemical concentrations by high performance liquid chromatography. Secondary metabolite concentrations ranged from traces to 2.94mg/g dry weight （DW） for pseudohypericin and traces -6.29mg/g DW for hyperforin. The differences in the secondary metabolite concentrations among populations of H. perforatum were found to be significant. The populations varied greatly in hyperforin concentrations, whereas they produced a similar amount of pseudohypericin. Concentrations of both secondary metabolites in all tissues increased with advancing of plant development and higher accumulation levels were reached at flowering. Among different tissues, full opened flowers were found to be superior to stems, leaves and the other reproductive parts with regard to pseudohypericin and hyperforin accumulations. The present findings might be useful to optimize the processing methodology of wild-harvested plant material and obtain increased concentrations of these secondary metabolites.展开更多
In this paper,we study the nonstationary population control systems:We regard the female-sum fertility rate β(t) as control auction ac judge its optimality by"norm minimum",and discuss the minimum norm cont...In this paper,we study the nonstationary population control systems:We regard the female-sum fertility rate β(t) as control auction ac judge its optimality by"norm minimum",and discuss the minimum norm control problems for the above population control systems.Utilizing space L2(0,T)’s reflexivity,smoothness and strict convexity,we prove the existence,the uniqueness and the approximation property of the minimum norm control for the nonstationary population control systems and give the corresponding optimality conditions by means of the methods of the dial mapping of Banach space.展开更多
In this paper, covariance structures with polytomous variables in several populations are analyzed. A computationally efficient multistage procedure is proposed to estimate the thresholds and the covariance structure ...In this paper, covariance structures with polytomous variables in several populations are analyzed. A computationally efficient multistage procedure is proposed to estimate the thresholds and the covariance structure parameters.Statistical properties of the estimators are derived, and a computer program is implemented to obtain the solution. An artificial example is presented to illustrate the method.展开更多
文摘Understanding how population sizes vary over time is a key aspect of ecological research. Unfortunately, our under- standing of population dynamics has historically been based on an assumption that individuals are identical with homogenous life-history properties. This assumption is certainly false for most natural systems, raising the question of what role individual variation plays in the dynamics of populations. While there has been an increase of interest regarding the effects of within popula- tion variation on the dynamics of single populations, there has been little study of the effects of differences in within population variation on patterns observed across populations. We found that life-history differences （clutch size） among individuals ex- plained the majority of the variation observed in the degree to which population sizes of eastern fence lizards Sceloporus undula- tus fluctuated. This finding suggests that differences across populations cannot be understood without an examination of differences at the level of a system rather than at the level of the individual
文摘The aim of this research was to evaluate the salinity tolerance in prairie grass populations at the seedling stage quantifying the variability and the influence of physiological traits related to it. Salinity tolerance, in </span><i><span style="font-family:Verdana;">Bromus</span></i> <i><span style="font-family:Verdana;">catharticus</span></i><span style="font-family:Verdana;"> Vahl (prairie grass) populations collected in different environments of the Pampean Phytogeography region (Argentine) was evaluated at the seedling stage, using controlled condition of temperature and light. It was adopted a completely randomized design using 3 plots with three plants each one per population and two levels of treatment: 0 mM and 100 mM NaCl. Morphological, biomass and membrane stability root and shoot traits were studied. A factorial ANOVA with interaction was estimated. Then one way ANOVA for all seedling traits in both treatments allowed estimating variance components, coefficient of genotypic determination (CGD) and variation index (VI). Comparisons between populations were made using Tukey test (at 5% of probability). Phenotypic correlations among traits were calculated and then a path coefficient analysis separated direct and indirect effects at 100 and 0 mM NaCl. No significant interactions “Population × Treatment” were found for any character. The saline stress caused a pairing in the population means for the most traits. Coefficients of variation were mainly higher when the seedlings grew without stress (0 mM) because it allowed a greater potential genotypic expression. The absence of significant interactions denotes a good homeostatic capacity of the prairie grass facing that abiotic stress. Leaf length, shoot length and root dry matter were the variables with the largest direct and indirect effects. Our results showed an increase for them at salt and demonstrated intraspecific variation, possibly in relation with the origin sites. Plants under stress showed a marked resilience, in order to quickly restore the same biomass allocation patterns that occur in non-stress environment.
基金supported by grants from FAPESP,CAPES and CNPq,Brazilian funding agencies for the promotion of science.
文摘A new idea on how to conceptually interpret the so-called Taylor’s power law for ecological communities is presented. The core of our approach is based on nonextensive/nonlinear statistical concepts, which are shown to be at the genesis of all power laws, particularly when a system is constituted by long-range interacting elements. In this context, the ubiquity of the Taylor’s power law is discussed and addressed by showing that long-range interactions are at the heart of the internal dynamics of populations.
文摘Hypericum perforatum is a perennial medicinal plant known as ＂St. John＇s wort＂ in Western Europe and has been used in the treatment of several diseases for centuries. In the present study, morphologic, phenologic and population variability in pseudohypericin and hyperforin concentrations among H. perforatum populations from Northern Turkey was investigated for the first time. The aerial parts of H. perforatum plants representing a total of 30 individuals were collected at full flowering from 10 sites of Northern Turkey to search the regional variation in the secondary metabolite concentrations. For morphologic and phenologic sampling, plants from one site were gathered in five phenological stages： vegetative, floral budding, full flowering, fresh fruiting and mature fruiting. The plant materials were air-dried at room temperature and subsequently assayed for chemical concentrations by high performance liquid chromatography. Secondary metabolite concentrations ranged from traces to 2.94mg/g dry weight （DW） for pseudohypericin and traces -6.29mg/g DW for hyperforin. The differences in the secondary metabolite concentrations among populations of H. perforatum were found to be significant. The populations varied greatly in hyperforin concentrations, whereas they produced a similar amount of pseudohypericin. Concentrations of both secondary metabolites in all tissues increased with advancing of plant development and higher accumulation levels were reached at flowering. Among different tissues, full opened flowers were found to be superior to stems, leaves and the other reproductive parts with regard to pseudohypericin and hyperforin accumulations. The present findings might be useful to optimize the processing methodology of wild-harvested plant material and obtain increased concentrations of these secondary metabolites.
文摘In this paper,we study the nonstationary population control systems:We regard the female-sum fertility rate β(t) as control auction ac judge its optimality by"norm minimum",and discuss the minimum norm control problems for the above population control systems.Utilizing space L2(0,T)’s reflexivity,smoothness and strict convexity,we prove the existence,the uniqueness and the approximation property of the minimum norm control for the nonstationary population control systems and give the corresponding optimality conditions by means of the methods of the dial mapping of Banach space.
基金This research is supported in part by a research grant DA01070 from the U.S. Public Health Service
文摘In this paper, covariance structures with polytomous variables in several populations are analyzed. A computationally efficient multistage procedure is proposed to estimate the thresholds and the covariance structure parameters.Statistical properties of the estimators are derived, and a computer program is implemented to obtain the solution. An artificial example is presented to illustrate the method.
