食饵和捕食者均染病的捕食-被捕食模型的分析

讨论一个食饵种群和捕食者种群同时感染疾病的捕食-被捕食模型,且考虑了由捕食者妊娠期引起的时滞.通过分析特征方程,得到了平衡位置的局部稳定和出现Hopf分支的条件,并且由此给出了食饵或者捕食者种群灭绝的阈值条件以及种群内部疾病的基本再生数;利用比较定理,研究了边界平衡位置的全局稳定性.     

具有多时滞影响的阶段结构捕食-被捕食模型研究

研究一个捕食者与被捕食者均有时滞影响的且捕食者只捕食幼年食饵的捕食-被捕食模型,通过构造适当的Lyapunov泛函,讨论了该模型的正平衡点与非负边界平衡点的渐进稳定性,从而得到了该生态模型的永久持续生存与灭绝的充分性条件。     

具有多时滞影响的阶段结构捕食—被捕食模型研究

研究一个捕食者与被捕食者均有时滞影响的且捕食者只捕食幼年食饵的捕食—被捕食模型,通过构造适当的Lyapunov泛函,讨论了该模型的正平衡点与非负边界平衡点的渐进稳定性,从而得到了该生态模型的永久持续生存与灭绝的充分性条件。     

一类具有三个成长阶段的捕食-被捕食模型的持久性和灭绝性

 讨论了一类食饵种群具有三个成长阶段的捕食-被捕食模型。通过构造Lyapunov泛函,讨论了模型的非负平衡点的吸引性,给出了两物种保持持久生存,捕食者种群灭绝,及两种群均灭绝的条件。     

具有时滞的生态-流行病SIS模型的分析

考虑了一类捕食者种群染病的捕食一被捕食模型,讨论了正平衡位置的局部稳定性,证明了时滞对正平衡位置稳定性的影响,以及当条件改变时系统在该点处会发生Hopf分支现象。     

一类具有传染病捕食与被捕食模型的稳定性

考虑了带有时滞和比率依赖且在捕食者中有传染病的捕食与被捕食模型,通过分析模型在灭绝平衡点,无病平衡点,共存平衡点相应的特征方程,利用微分方程理论,讨论了模型在平衡点的局部稳定性,并用数值模拟验证结果.     

捕食率对一类食饵-捕食者动力学模型稳定性的影响

在传统的食饵-捕食者模型中引入一个新的中间物种,该中间物种捕食原模型中的食饵,又被原捕食者所捕食,采用Logistic人口模型和Holling-I型功能响应函数给出这三个物种的动力学方程模型,解析得到该模型的平衡点以及它们的存在条件.利用雅可比矩阵和Routh-Hurwitz判据分析了平衡点的稳定性.数值模拟结果发现捕食率对捕食者自身的生存与灭绝具有十分重要的意义.     

具有Beddington-DeAngelis型功能反应的捕食系统的稳定性分析

研究了两类具有竞争关系的食饵种群被一类具有阶段结构和时滞的捕食者捕食,且具有Beddington-DeAngelis型功能反应的捕食系统.通过比较原理获得该系统持续生存和捕食者灭绝的充分条件,并且当系统为周期系统时,获得其正周期解存在性和全局稳定性的充分条件.     

食饵种群具有存放率的第Ⅲ类功能性反应模型的定性分析

本文研究了非密度制约的捕食与被捕食系统中被捕食者种群具有常数存在率的第Ⅲ类功能性反应模型,给出了该系统极限环的不存在性,存在性及唯一性的条件。     

一类具有阶段结构的捕食模型的稳定性

对一类具有时滞和阶段结构的Lotka-V o lterra型捕食模型进行了分析.利用上、下解方法及相应的单调迭代序列研究具有时滞的耦合半线性抛物方程组的动力学行为,给出了解的渐近性质.结果表明:扩散并不影响种群的生存和灭绝,而捕食者的阶段结构对其生存具有负面影响.     

一类三种群混合扩散模型的持续生存

本文对一类三种群混合扩散模型进行研究，得到了扩散对系统持续生存影响的充分条件，表明即使食饵种群在某些孤立斑块中可能绝灭，也可以通过适当选取扩散率来保证系统持续生存。     

Food-web interactions govern the resistance of communities after non-random extinctions

Growing concern about how loss of biodiversity will affect ecosystems has stimulated numerous studies. Although most studies have assumed that species go extinct randomly, species often go extinct in order of their sensitivity to a stress that intensifies through time (such as climate change). Here we show that the consequences of random and ordered extinctions differ. Both depend on food-web interactions that create compensation; that is, the increase of some species when their competitors and/or predators decrease in density due to environmental stress. Compensation makes communities as a whole more resistant to stress by reducing changes in combined species densities. As extinctions progress, the potential for compensation is depleted, and communities become progressively less resistant. For ordered extinctions, however, this depletion is offset and communities retain their resistance, because the surviving species have greater average resistance to the stress. Despite extinctions being ordered, changes in the food web with successive extinctions make it difficult to predict which species will show compensation in the future. This unpredictability argues for 'whole-ecosystem' approaches to biodiversity conservation, as seemingly insignificant species may become important after other species go extinct.     

脉冲作用对环境污染中单种群动力学行为影响

研究了一个在污染环境中的单种群模型,该模型考虑外界污染源在固定时刻排放毒素到本环境中以及在同一时刻考虑通过一些因素作用使该种群生物体排泄毒素.利用脉冲微分方程的比较定理及周期单种群Logistic模型的一些已知结论,证明了当脉冲周期小于某个阈值时,该种群灭绝,反之,则该种群持续生存.并且还证明了上述的持续生存条件也能确保该系统存在惟一的全局渐近稳定的正周期解.     

Tree species impoverishment and the future flora of the Atlantic forest of northeast Brazil

Estimates of species extinction due to human impact on tropical forests have previously been based on the relationship between species number and area. Here we use a different approach to estimate loss of tree species in the Atlantic forest of northeast Brazil. We evaluate the characteristics of plant species, their avian dispersers and the distribution of the forest remnants on the landscape to estimate that about 33.9% of tree species in this region will become extinct on a regional scale. Because northeast Brazil is the most threatened sector of South American Atlantic forest, our results highlight the need to change the current conservation paradigm for this region. Rather than focus on the creation of isolated reserves in any medium-to-large forest remnant, a bioregional planning approach is urgently required to rescue this unique biota from extinction.     

中草药产业持续发展的目标要求与基本对策

中医药是中华民族的瑰宝,但随着人类经济活动对资源的利用、对环境的影响和这一产业的快速发展,许多重要药用野生资源出现了渐危、濒危甚至灭绝的现象,在一定程度上已经影响到中草药产业的持续发展。为此,应明确中草药产业可持续发展的目标要求,从增强保护意识、加快法律体系建设、保护资源的持续利用和中医药的科研、教育等方面入手,实现中草药产业可持续发展。     

具有反馈控制变量的偏害模型稳定性研究

研究具有反馈控制变量的两种群偏害共生模型正平衡点的稳定性.通过构造适当的Lyapunov函数,讨论系统的全局稳定性.研究表明,如果原系统是全局稳定的,反馈控制变量仅改变正平衡点的位置,使得种群平衡密度变小,不会改变正平衡点的稳定性;如果原系统是绝灭的,加入适当的反馈控制变量,可以使绝灭的种群变稳定.     

Ecology: is speciation driven by species diversity?

Emerson and Kolm show that the proportion of species endemic to an island is positively related to its species richness and, assuming that endemism indexes speciation rate, they infer that greater species diversity accelerates diversification. Here we demonstrate that the same correlation between species richness and percentage endemism can arise even if within-island speciation is negligible, particularly when both endemism and species richness depend on attributes of islands (such as area) that influence the average age of resident populations. Island biogeography theory indicates that, where the average time to extinction is relatively long, diversity increases through colonization, irrespective of whether new species are formed; at the same time, islands on which populations persist for longer accumulate more endemic species as local populations differentiate and populations on neighbouring islands become extinct. We therefore suggest that species richness and endemism are correlated fortuitously owing to their mutual dependence on the life spans of populations on islands, which is unrelated to speciation itself.     

陕西红碱淖遗鸥研究现状分析

遗鸥（Larus relictus）是世界珍稀濒危鸟类,国家Ⅰ级保护鸟类,是确立较晚的物种。我国主要繁殖和栖息地分布在内蒙古鄂尔多斯桃力庙-阿拉善湾海子和陕西神木红碱淖湿地,目前红碱淖遗鸥种群的数量已经远胜于桃力庙-阿拉善湾海子,成为全球最大遗鸥繁殖种群,有关学者对其开展了一些研究工作。本文从种群的分布、分类学、生态学...     

一类疾病额外死亡率存在的传染病模型

对一类疾病额外死亡率存在的两种群相互竞争的非自治Ｓ（易感者）－Ⅰ（染病者）－Ｓ（易感者）传染病模型进行了研究。发现了无疾病额外死亡率存在两种群持续生存的条件下，若引入疾病额外死亡率，则两种群可能依然持续生存，也可能一种群持续生存，另一种群绝灭。但是，两种群不可能同时绝灭，并且在两种群共存的情况下，讨论了周期解的存在性与全局渐近稳定性。