【作者】 王林；

【导师】 王瑞武；

【作者基本信息】 西北工业大学 ， 生物医学工程， 2020， 博士

【摘要】 在全球变暖的当下,物种灭绝日益加剧,研究和保护物种的多样性已刻不容缓。基于此,生态学家主张深入理解“物种多样性-系统稳定性-结构复杂性”这一核心问题。然而,时至今日,有关“物种多样性与系统稳定性关系”、“物种共存的一般机制”以及“自然群落中的种群混沌与灭绝”等话题一直受到生态学家的广泛讨论,相关的机制研究仍未达成共识。本文结合实验/野外数据的相空间重构技术和动力系统理论以探究群落(聚果榕系统、浮游生物群落和大西洋鳕种群)的复杂动态行为,其主要包括理论分析物种共存、物种多样性与群落稳定性关系,群落混沌动态的实证研究以及生态-进化混沌研究三个方面的内容。具体研究结果如下:1.以榕树-榕小蜂群落为模型系统建立相应的食物网模型,并将群落结构引入到“多样性-稳定性”争论中。模型仿真结果表明,传粉蜂的拟寄生蜂种群密度对榕小蜂多样性有促进作用,拟寄生蜂种群的自上而下控制对群落多样性和稳定性有调节作用。此外,只有中等程度的寄生性才会导致榕树-榕小蜂群落中物种周期/混沌共存,而种群混沌可以维持榕小蜂的多样性。当榕小蜂的多样性较低时,增加榕小蜂多样性可以增加群落的稳定性。2.基于两种自然群落(浮游生物群落、榕树-榕小蜂群落)的网络结构,推导出一般性的杂食性食物网模型。在不同资源水平以及兼性捕食者的捕食偏好改变的情况下,分析食物网结构和稳定性的变化情况。模型分析结果表明,弱捕食强度可以促进物种间的稳定共存;而杂食性、增加的竞争作用、自上而下控制和自下而上控制均能促进物种多样性和食物网稳定性。3.基于野外数据分析与数学模型仿真相结合的方法,探究榕树-榕小蜂共生系统中种群的混沌波动和群落的稳定维持。首先,建立一个离散的、带有季节性环境波动的宿主-传粉者-剥削者模型,并采用Levenberg-Marquardt优化算法拟合野外数据。参数化的模型预测种群混沌可能是宿主调控与环境变化共同作用的结果。模型模拟表明,当外部环境变化(如季节温度)较小时,宿主会降低宿主奖励与惩罚之比(RS)来维持自身较高的种群密度。4.以浮游生物群落为模型系统,将季节性温度纳入带有捕食偏好的食物网模型。并利用马尔可夫链蒙特卡罗(MCMC)算法估计模型参数。模型仿真表明,内部因素(桡足类的种内竞争系数)和外部因素(季节性温度)共同导致浮游生物群落中种群混沌。同时,相空间重构分析表明,实验数据的Lyapunov指数为正。理论预测和实验数据都表明,浮游生物群落呈现出混沌动态。5.以大西洋鳕种群为模型系统,结合实验数据和生态-进化模型来揭示鳕鱼体长的混沌动态。首先,基于相空间重构技术的鱼体长数据的最大Lyapunov指数为正数,它与由生态-进化模型计算的平均Lyapunov指数数值接近,表明鳕鱼种群存在生态-进化混沌的可能性。其次,实验数据和生态-进化模型仿真数据的自相关函数(ACF)分析都显示了大约7年的相似滞后。本论文主要的创新性包括:首先,提出一类不同群落共有的食物网结构,分析了该食物网中多物种共存的一般机制问题;其次,结合理论模型和野外自然数据证实了榕树-榕小蜂系统的种群混沌动态,并给出了混沌产生的机制;最后,揭示了鳕鱼体长的生态-进化混沌现象。本研究将重新审视群落复杂动态(混沌)背后的深层次驱动力以及物种多样性、物种共存的维持条件,为保护生物多样性提供理论支持。更多还原

【Abstract】 With global warming and the increasing extinction of species,it is imperative to study and protect species diversity.On this basis,ecologists advocate a deeper understanding of the core problem of "species diversity-system stability-structural complexity".However,up to now,topics such as "the relationship between species diversity and system stability","the general mechanism of species coexistence" and "population chaos and extinction in natural communities" have been widely discussed by ecologists.Unfortunately,there is still no consensus on the mechanisms involved.In this thesis,the complex dynamic behaviour of communities(i.e.Ficus racemosa,plankton community and Gadus morhua)was explored by combining the phase-space reconstruction technique of experimental/field data and dynamic system theory.The thesis mainly includes:theoretical analyses of species coexistence and diversity-stability debate,empirical study on community chaos,and eco-evolutionary chaos.Specific research results are listed as follows:1.With fig species and their associated fig wasp community as model system,this research brings community structure into the ‘diversity-stability’ debate by establishing the fig-fig wasp food web model.The simulations of the model indicated that wasp diversity was promoted by population density of the parasitoids of the pollinating wasps,and that top-down control from the parasitoids regulated community diversity and stability.Moreover,only moderate parasitoidism on the pollinators resulted in the regular/chaotic coexistence,while population chaos would maintain wasp diversity in the fig-fig wasp system.Increases in the wasp diversity could increase community stability when biodiversity of fig wasps was low.2.This research established an omnivorous food web model based on the network structure of two natural ecosystems(plankton community and fig-fig wasp system).It analyzed the changes of both food web structure and stability under the different resource levels and predation preference of the generalist predator.The results of model analyses showed that weak predation strength can promote stable coexistence,and an integration of omnivory,increased competition,top-down control and bottom-up control can promote species diversity and food web stability.3.This research combined field data with a mathematical model to explore the population fluctuations and the maintenance of stability in the fig-fig wasp system.First,a discrete,seasonally explicit host-mutualist-exploiter model was estabolished and Levenberg-Marquardt optimization algorithm was adopted to fit fig-wasp field data.The model parameterized with field data predicted that population chaos could be a result of interactions between host regulation and environmental variation.Model simulations showed that the host decreased the strength in the ratio of extra reward to host sanction(RS)to maintain its higher population density when the external environment variation(e.g.,seasonal temperature)is small.4.This research simulated plankton system via combining both seasonal temperature and a food web model with prey preference,and further used the Markov chain Monte Carlo(MCMC)algorithms to estimate model parameters.Theoretical predictions showed both internal factor(intraspecific competition coefficient of calanoid copepods)and external factor(seasonal temperature)are the key factors,which can produce population chaos.Meanwhile,phase space reconstruction method showed Lyapunov exponents of empirical data are positive.Both theoretical predictions and empirical data showed the plankton community presents the chaotic dynamics.5.With Gadus morhua as model system,this research combined analyses of empirical data and an eco-evolutionary model to uncover the chaotic dynamics of body length in a fish population(northeast Atlantic cod: Gadus morhua).Consistent with chaotic attractors,both the largest Lyapunov exponent(LE)of empirical data was positive and approximately matched the LE of the theoretical model calculation,thus suggesting the potential for eco-evolutionary chaos in this fish population.The research also found that the autocorrelation function(ACF)of both empirical data and eco-evolutionary model showed a similar lag of approximately 7 years.The main innovations of this thesis include: first of all,the structure of a food web shared by different communities was proposed,and general mechanisms of multi-species coexistence in the food web were analyzed.Moreover,the chaotic dynamics of fig-fig wasp system was confirmed by combining theoretical model and field data,and the mechanism of population chaos was given.Finally,the eco-evolutionary chaos of body length in a fish population(Gadus morhua)was revealed.This thesis will re-examine the underlying driving forces behind the complex dynamics(e.g.chaos)in ecological communities and the maintenance conditions for species diversity and species coexistence,so as to provide theoretical support for biodiversity conservation.更多还原