Leslie系统在污染环境下有关生存问题的分析

研究了在污染环境中毒素对Leslie资源-消费者系统中消费者种群的长期影响,给出了种群弱持续生存和灭绝的条件．     

自然条件下同级消费者中种群平均规模的博弈论研究

给出了一种新的博弈——非合作n人条件博弈,并给出了它的求解方法．以这种博弈为工具,在适当的假定下研究了无人类的理想地域上同级消费者中各个种群的平均规模．结论是:当个体的平均食量充分小时,该种群的平均规模等于前一级消费者或生产者的最大承受量;否则该种群的平均规模与前一级消费者或生产者的最大承受量成正比,与个体的平均食量和该级消费者中种群的数目都成反比．     

高寒草甸消费者种群稳定碳、氮同位素组成的海拔分异

通过测定青藏高原东部高寒区不同海拔主要植物和消费者种群（雀形目鸟类和小型哺乳类）的稳定碳、氮同位素比值,研究了高寒草甸消费者种群同位素组成特征及其影响因素。结果表明：植物平均稳定碳同位素随海拔升高表现出明显的增加趋势;消费者种群稳定碳、氮同位素随海拔的升高有明显的富集效应。雀形目鸟类种群稳定碳、氮同位素随海拔的升高均呈明显增加趋势;小型哺乳类稳定碳同位素随海拔上升不明显,而稳定氮同位素具有明显的增大趋势。消费者种群稳定碳、氮同位素沿海拔梯度的富集效应,一方面与植物稳定同位素在海拔梯度上的富集密切相关;另一方面与海拔和纬度变化所引起一系列环境因子的变化在一定程度上影响到动物的稳定同位素分布模式。另外,在高寒草甸地区,与雀形目鸟类相比,小型哺乳类在动物稳定同位素组成的代谢过程中更容易受到环境改变的影响。     

高寒草旬消费者种群稳定碳、氮同位素组成的海拔分异

通过测定青藏高原东部高寒区不同海拔主要植物和消费者种群（雀形目鸟类和小型哺乳类）的稳定碳、氮同位素比值,研究了高寒草甸消费者种群同位素组成特征及其影响因素。结果表明：植物平均稳定碳同位素随海拔升高表现出明显的增加趋势;消费者种群稳定碳、氮同位素随海拔的升高有明显的富集效应。雀形目鸟类种群稳定碳、氮同位素随海拔的升高均呈明显增加趋势;小型哺乳类稳定碳同位素随海拔上升不明显,而稳定氮同位素具有明显的增大趋势。消费者种群稳定碳、氮同位素沿海拔梯度的富集效应,一方面与植物稳定同位素在海拔梯度上的富集密切相关;另一方面与海拔和纬度变化所引起一系列环境因子的变化在一定程度上影响到动物的稳定同位素分布模式。另外,在高寒草甸地区,与雀形目鸟类相比,小型哺乳类在动物稳定同位素组成的代谢过程中更容易受到环境改变的影响。     

不同初始密度棉蚜种群动态过程

为探索棉蚜初始密度对其种群过程的影响,在棉田控制1和20头·叶-1 2个初始密度,通过尼龙网纱袋构建在封闭(套袋)与开放(不套袋)条件下,监测棉蚜在不同初始密度和不同环境条件下种群动态.结果表明:初始密度越大,棉蚜种群峰值越高,封闭条件和开放条件棉蚜种群峰值没有显著性差异;初始密度越大种群高峰期越早,开放条件比封闭条件种群高峰期提前;封闭条件下,初始密度越大,种群崩溃越快.种群发展初期,初始密度越小,种群增长率越大,开放条件比封闭条件棉蚜种群增长快;种群高峰期和崩溃期,不同初始密度棉蚜种群增长率没有显著差异.初始密度影响有翅蚜形成,初始密度越大,有翅蚜比例越高;但封闭条件和开放条件有翅蚜比例没有显著性差异.     

腾格里沙漠东南缘白刺种群性状对沙埋的响应

运用实验生态学和数量生态学方法,研究了腾格里沙漠东南不同沙埋程度的白刺(Nitraria tangutorum)种群特征,并就各特征与沙埋深度的关系进行了分析.结果表明:强沙埋条件(湖盆低地)白刺种群特征均值都大于弱沙埋条件(山前冲积扇),但白刺种群各特征变异却是强沙埋条件小于弱沙埋条件;除弱沙埋条件白剌种群密度外,其他各性状都与沙埋有着显著相关关系;强沙埋条件的种群各性状发育最适沙埋深度均大于弱沙埋条件下;不论沙埋深度强弱和最适沙埋深度的高低,白刺种群各性状发育均受最适沙埋深度制约;低于最适沙埋深度,沙埋深度增加促进种群性状发育,高于最适沙埋深度,沙埋深度增加抑制种群性状发育.白刺种群各性状对沙埋深度的响应主要体现在高生长和生物量上:盖度和密度的发育不仅受沙埋的影响,更主要是受沙埋深度影响下的其他资源特别是水分的限制.     

青藏高原东缘匍匐茎草本野草莓的分株种群特征及其沿海拔梯度的变化

对青藏高原东缘 5个不同海拔高度 ( 2 4 2 6m、2 75 0 m、32 0 0 m、3484m和 3944m)上旷地和林下遮荫条件下匍匐茎草本野草莓的分株种群特征进行了研究。结果显示 :无论在旷地或林下遮荫条件下 ,野草莓分株种群的密度随海拔升高显著减小 ,旷地条件下野草莓分株种群密度显著高于遮荫条件下的分株种群密度。不同海拔高度上 ,野草莓分株种群密度在不同光照条件下的变化存在显著差异。旷地条件下 ,随海拔升高其根冠比呈二次曲线变化。林下遮荫条件下 ,海拔 2 4 2 6m处的根冠比最低。光照条件的变化对野草莓分株种群的根冠比没有显著影响。运用空间自相关分析法 ( Moran` I)研究和 3944m处野草莓分株种群的空间分布格局 ,结果显示野草莓分株种群在多个尺度上呈现非随机分布格局 ,其中研究了海拔 348m处 d=1( 0 .2 m)尺度的集聚分布格局频率最高 ;与海拔 3484m相比 ,3944m处野草莓分株种群的集聚尺度更大。最后 ,结合克隆植物对环境的生态适应意义进行了讨论。     

具有毒素输入和扩散的种群模型的一致持久性

本文研究两个描述种群和毒素相互作用的种群模型的渐近性态。在有种群扩散和毒素扩散的假设下,建立了种群一致持久的条件。     

温度对星豹蛛实验种群增长的影响

根据星豹蛛(Pardosa astribera Koch)在20℃、23℃、29℃、32℃和35℃6种恒温条件下的发育历期、幼蛛存活率、成蛛产卵率、产卵量和孵化率组建了星豹蛛在不同温度条件下的实验种群增长表,结果表明星豹蛛在所试验的6种恒温条件下其种群数量可保持上升趋势,其中以在29℃条件下种数量增长最快、繁殖1代种群数量对增加37.78倍;以在20℃的条件下种群数量增长最慢,繁殖1代其中种群数量可增加15.77倍。     

温度对玉米蚜种群增长的影响

研究了温度对玉米蚜RhopalosiphummaidisFitch种群存活率、生殖率及内禀增长率的影响 ,同时测定了不同温度条件下玉米蚜种群的净增殖率、周限增长率、种群倍增时间及稳定年龄组配等种群参数。在 1 0℃和 3 5℃条件下 ,玉米蚜若蚜的死亡率较高 ,特别是 4龄若蚜 ;2 5℃最适宜玉米蚜的生长、发育和繁殖 ,其种群增长最快     

Persistence and extinction of a stochastic single-specie model under regime switching in a polluted environment

A new single-species model disturbed by both white noise and colored noise in a polluted environment is developed and analyzed. Sufficient criteria for extinction, stochastic nonpersistence in the mean, stochastic weak persistence in the mean, stochastic strong persistence in the mean and stochastic permanence of the species are established. The threshold between stochastic weak persistence in the mean and extinction is obtained. The results show that both white and colored environmental noises have sufficient effect to the survival results.     

Survival Analysis of Stochastic Competitive Models in a Polluted Environment and Stochastic Competitive Exclusion Principle

Stochastic competitive models with pollution and without pollution are proposed and studied. For the first system with pollution, sufficient criteria for extinction, nonpersistence in the mean, weak persistence in the mean, strong persistence in the mean, and stochastic permanence are established. The threshold between weak persistence in the mean and extinction for each population is obtained. It is found that stochastic disturbance is favorable for the survival of one species and is unfavorable for the survival of the other species. For the second system with pollution, sufficient conditions for extinction and weak persistence are obtained. For the model without pollution, a partial stochastic competitive exclusion principle is derived.     

Persistence and extinction of a population in a polluted environment

Models of the persistence and extinction of a population or community in a polluted environment have been investigated in several papers. But all of those papers have a basic assumption that the capacity of the environment is so large that the change of toxicants in the environment that comes from uptake and egestion by the organisms can be neglected. This assumption is not made in this article. Some sufficient conditions on persistence or extinction of a population have been obtained, and the threshold between the two has also been obtained for most situations.     

Persistence and extinction of a stochastic single-specie model under regime switching in a polluted environment II

This is a continuation of our paper [Liu, M., Wang, K., 2010. Persistence and extinction of a stochastic single-specie model under regime switching in a polluted environment, J. Theor. Biol. 264, 934-944]. Taking both white noise and colored noise into account, a stochastic single-species model under regime switching in a polluted environment is studied. Sufficient conditions for extinction, stochastic nonpersistence in the mean, stochastic weak persistence and stochastic permanence are established. The threshold between stochastic weak persistence and extinction is obtained. The results show that a different type of noise has a different effect on the survival results.     

二维Lotka-Volterra竞争系统的β持续生存与β绝灭

利用极限理论与延拓方法研究了二维Lotka-Volterra竞争务统在有限时间内的持续生存与绝灭问题,即β持续生存与β绝灭问题.给出了种群β持续生存与β绝灭的一些充分条件.所得结论表明:种群的β持续生存和β绝灭与种群的初始数量有关.在一定条件下,只要控制种群的初始数量在一定范围内,即可保证两种群永远β持续生存.     

Importance of metapopulation dynamics to explain fish persistence in a river system

1. Habitat modification and fragmentation are key factors responsible for fish population decline worldwide. Previous assessments documented a total of 72 species extinctions for the sole class of Actinopterygii. However, global extinctions are difficult to monitor or study based on fossil records. By contrast, local extinctions occurring at the population level are easier to study. Given this context, an important question relates to whether extinction dynamics studied at the local scale can provide useful information to understand extinctions occurring at larger scales. This would be the case if local extinctions were not balanced by recolonisation as in a classic metapopulation. Our aim is thus to explain the observed regional (per basin) persistence of 252 fish populations by testing contribution of local extinction rates and more generally metapopulation dynamics components.
2. To address this aim, we used the annual extinction probability of 252 regional populations of up to 14 species inhabiting 18 coastal rivers, which became isolated c. 8,500 years ago. We specifically compared extinction probabilities obtained by seven theoretical models to investigate whether regional extinction rates (i.e. loss from a river system) were correlated to local extinction rates (i.e. loss from an occupied site) and the role of metapopulation dynamics to explain regional persistence.
3. Using empirical data, we showed the importance of variables related to metapopulation dynamics to explain extinction rates across the 18 river systems. As expected, the regional extinction rate decreased with the colonisation rate, area, metapopulation size, and percentage of occupied localities. By contrast, an inconsistent relationship emerged between regional and local extinction rates, as species with high local extinction rates were not particularly prone to regional extinction.
4. Our results provide strong support for the contribution of colonisation rates to explain persistence. Overall, our results show that the equilibrium number of occupied localities could be a good predictor of the long-term persistence of metapopulations in rivers. Finally, our results suggest the importance of connectivity to maintain sustainable populations within the river system.

     

The intrinsic mean time to extinction: a unifying approach to analysing persistence and viability of populations

Analysing the persistence and viability of small populations is a key issue in extinction theory and population viability analysis. However, there is still no consensus on how to quantify persistence and viability. We present an approach to evaluate any simulation model concerned with extinction. The approach is devised from general Markov models of stochastic population dynamics. From these models, we distil insights into the general mathematical structure of the risk of extinction by time t, P₀(t). From this mathematical structure, we devise a simple but effective protocol – the ln(1−P₀)-plot – which is applicable for situations including environmental noise or catastrophes. This plot delivers two quantities which are fundamental to the assessment of persistence and viability: the intrinsic mean time to extinction, T_m, and the probability c₁ of the population reaching the established phase. The established phase is characterized by typical fluctuations of the population's state variable which can be described by quasi-stationary probability distributions. The risk of extinction in the established phase is constant and given by 1/T_m. We show that T_m is the basic currency for the assessment of persistence and viability because T_m is independent of initial conditions and allows the risk of extinction to be calculated for any time horizon. For situations where initial conditions are important, additionally c₁ has to be considered.     

Asynchronization of local population dynamics and persistence of a metapopulation: a lesson from an endangered composite plant, Aster kantoensis

Fragmentation of a large habitat makes local populations less linked to others, and a whole population structure changes to a metapopulation. The smaller a local population is, the more strengthened extinction factors become. Then, frequent extinctions of local populations threaten persistence of the metapopulation unless recolonizations occur rapidly enough after local extinctions. Spatially structured models have been more widely used for predicting future population dynamics and for assessing the extinction risk of a metapopulation. In this article, we first review such spatially structured models that have been applied to conservation biology, focusing on effects of asynchronization among local population dynamics on persistence of the whole metapopulation. Second, we introduce our ongoing project on extinction risk assessment of an endangered composite biennial plant, Aster kantoensis, in the riverside habitat, based on a lattice model for describing its spatiotemporal population dynamics. The model predicted that the extinction risk of A. kantoensis depends on both the frequency of flood occurrence and the time to coverage of a local habitat by other competitively stronger perennials. Finally, we present a measure (Hassell and Pacala's CV ²) for quantifying the effect of asynchronization among local population dynamics on the persistence of a whole metapopulation in conservation ecology. Received: January 12, 2000 / Accepted: February 8, 2000     

一类非自治SIRS传染病模型的持久性与灭绝性研究

本文研究了一类非自治SIRS传染病模型．在比较弱的条件下,我们不仅得到了疾病强一致持续的充分必要条件,还证明了疾病强一致持续与强持续的等价性．本文给出了新的闽值．另外也给出了疾病灭绝的条件．文献[7]中的结论被改进．