温度对麦长管蚜种群存活率的特征参数的影响

在测定麦长管蚜种群存活率基础上,本提出反S型曲线模型来描述种群存活率,探讨了麦长管蚜种群存活率过程变化的特征参数,并得到不同的特征值．     

一类单种群动态模型的稳定性

一、引言及引理考虑一类单种群动态模型对方程（1）总假设满足其中N（t）为种群在时刻t的数量或密度．由于方程（1）是描述种群增长的生态模型,因此我们考虑（1）的正解且满足初始条件：易证（1）和（2）有唯一正常数平衡点本文研究（1）关于N*的稳定性．（1）的特别情形是其中（1a）描述在食物资源严重不足种群数量充分大导致种群内部互相竞争残杀时的增长模型［1];（1b）描述种内既有竞争又有协作的所谓ALLEE效应的增长模型［2]．事实上,若β＞0,由（1b）式知,当N（t-r）充分小时,当N（t—r）充分大时,这正是ALLEE效应．文献…     

两个种群随机共进化动态

本文研究同时考虑内外部博弈的两个种群的随机进化动态,博弈的双方个体既可以来自不同种群,也可以来自同一种群,不同种群个体之间的博弈为非对称的,同一种群个体之间的博弈为对称的.我们首先介绍由四个收益矩阵描述的两个种群博弈模型,然后通过突变-选择Moran过程分析了这种随机共进化过程,最后推导出中性选择及弱选择时策略均衡频率的公式.     

羊草种群无性系生长格局的研究

 本文根据野外实测数据和采用数学分析方法,在研究羊草种群无性系营养扩散和生长过程的基础上,建立了符合描述羊草种群无性系生长格局的相关随机走动模型和简单扩散模型。对模型进行检验,结果表明,所建模型可以定量地描述羊草种群无性系的生长格局。     

昆虫种群的生长──扩散模型研究

根据昆虫种群生长规律和空间扩散规律,本文提出了建立昆虫种群生长-扩散统一模型的条件,并提出了12种可能的生长-扩散统一模型．其中的模型包括了指数增长（减少）,逻辑斯蒂增长和威布尔生长规律,同时包括幂率衰减,指数衰减和随机扩散等扩散规律;同时这些模型可以单独描述单一的生长过程或扩散过程。文中以水稻害虫青翘蚁形隐翘虫的扩散和种群数量消长为例,研究了文中模型的应用问题,结果表明本文的模型用于描述昆虫种群的方向性扩散一指数衰减生长的过程是合适的。     

异质种群动态模型:破碎化景观动态模拟的新途径

景观破碎化导致物种以异质种群方式存活,使得基于异质种群动态模拟破碎化景观动态成为可能。异质种群动态模型的发展为景观动态模拟奠定了良好基础。根据空间处理方式的不同,异质种群模型可分为三大类,可不同程度地用于描述破碎化景观动态。(1)空间不确定异质种群模型,假定所有局域种群间均等互联,模型中不包含空间信息,仅能用于景观斑块动态描述;(2)空间确定异质种群模型,假设局域种群在二维空间上以规则格子形式排列,是一种准现实的空间处理方式,可用于景观动态的简单描述;(3)空间现实异质种群模型,包含了破碎化景观中局域种群的几何特征,可直接用于真实景观动态的模拟研究。空间现实的和基于个体的异质种群模型不但是未来异质种群模型发展的主流,也将成为未来破碎化景观动态研究的重要工具。为了更加准确完整地描述破碎化景观动态,不但应该综合运用已有的各种异质种群模型方法,更要引进新模型来刎画多物种、多变量、高维度、复杂连接的破碎化景观格局与过程。     

集合种群空间混沌的模拟研究以及Allee效应、拥挤效应与捕食效应对空间模式的影响

集合种群的空间模式研究是当今生态学的核心问题之一。本研究利用常微分动力系统以及基于网格模型的元胞自动机模型对Allee效应、拥挤效应以及捕食作用集合种群的空间分布模式做了全面的模拟研究。Allee效应描述当种群水平低于某一阈值时会发生由生殖成功几率下降造成的种群负增长率,而拥挤效应是指当种群密度过高时引起的个体性为异常从而达到调节种群增长率的作用。文章组建了3个空间确定性模型：局部作用模型(CIM)、距离敏感模型(DSM)和集合种群捕食模型(MMP)。局部作用模型显示在一维生境中空斑块形成金字塔状,二维模型显示出明显的动态拟周期性以及由空间混沌所形成的异质性。距离敏感模型可导致由迁移个体中密度制约强度决定的集合种群大小复杂动态与种群密度的双峰分布。这些结果说明动态行为的复杂性,不仅可用于表征研究物种的特性,而且可以表明该物种的续存能力与灭绝风险。集合种群捕食模型是概率转换空间模型,利用该模型得出了依赖于模型参数和生境尺度的白组织种群概率空间分布模式。模拟的结果表明,系统的内在机制和这种白组织模式导致捕食者形成集团型不明显的“捕食小组”或“杀手小组”,并具有较高扩散力．但却包括侵占率低、灭绝率高的特点。而使猎物种群形成高集团性、高侵占率、低灭绝率、低扩散力的种群集团。这种特点又使捕食者种群在生境中处于中心地带,而使猎物种群形成在捕食者和生境边缘间的环状分布。这些结果还说明了尺度对于生态学的研究是至关重要的,不同的尺度将产生不同的系统模式。     

运动昆虫密度和疾病传染数量估计的两类模型

根据推导,得到用于运动昆虫密度和疾病接触传染数量估计的二维和三维空间模型．两类模型分别适用于爬行昆虫和飞行昆虫的种群密度估计．二维空间模型可用于描述昆虫疾病的接触传染数量,针对不同的用途,将两类基本模型进行了数种拓广.两类模型的建立,为运动昆虫的密度估计及疾病流行研究提供了重要的定量工具．     

动物种群动态模型研究的进展与展望

动物种群动态模型经历了百余年的发展, 文章回顾和总结了其取得的丰富成果, 并展望其未来发展方向。种群动态包括种群数量动态和时空分布动态, 根据其形式和研究内容,可以将种群动态模型分为数量模型和空间模型。数学模型通过数学方程模拟种群数量的变化趋势, 它包括“J”型增长模型、“S”型增长模型和Lotka-Voltera模型等; 空间模型侧重于种群和生境的空间化表达, 包括异质种群模型、空间精确性种群模型和基于个体的种群模型等。种群动态模型在物种保护、气候变化和土地管理等方面都有成功应用。目前, 种群动态模型的空间描述能力不足, 未来与地理信息技术结合将有助于种群动态模型的进一步发展。     

广义Logistic模型的拟合

给出了广义Logistic模型有显示解的存在定理及其参数的一种拟合方法,并以稻田捕食天敌种群数量变化进行实际拟合,从而验证该模型对于描述各种不同生物种群的动态有更广泛的适用性。     

Sex,competition and mimicry: an eco-evolutionary model reveals unexpected impacts of ecological interactions on the evolution of phenotypes in sympatry

Phenotypic evolution in sympatric species can be strongly impacted by species interactions, either mutualistic or antagonistic. Heterospecific reproductive behaviours between sympatric species have been shown to favour phenotypic divergence of traits used as sexual cues. Those traits may also be involved in local adaptation or in other types of species interactions and, as a result, undergo complex evolutions across sympatric species. Here we focus on mimicry and study how reproductive interference may impair phenotypic convergence between species with various levels of defence. We use a deterministic model assuming two sympatric species where individuals can display two different warning colour patterns. This eco-evolutionary model explores how ecological interactions shape phenotypic evolution within sympatric species. We investigate the effect of 1) the opposing density-dependent selections exerted on colour patterns by predation and reproductive behaviour and 2) the impact of relative species and phenotype abundances on the fitness costs faced by each individual depending on their species and phenotype. Our model shows that reproductive interference may limit the convergent effect of mimetic interactions and may promote phenotypic divergence between Müllerian mimics. The divergent and convergent evolution of traits also strongly depends on the relative species and phenotype abundances and levels of trophic competition, highlighting how the eco-evolutionary feedbacks between phenotypic evolution and species abundances may result in strikingly different evolutionary routes.     

Differences in sensory projections between macro- and microchaetes in Drosophilid flies

From examination of the central axonal projections of sensory bristles on the notum of several species of Drosophilidae, we demonstrate different features that may indicate different functions for macro- and microchaetes. The large macrochaetes have conserved arborizations that correlate with their conserved position. Nevertheless, we find evidence for only two discrete projection patterns for bristles in the dorsocentral (DC) row, even when there may be four or five bristles present. We show that the small microchaetes of Drosophila melanogaster display regional specificity and subsets of contiguous bristles project to a common region in the thoracic ganglion. Interestingly, the axons of each of these subsets also form a specific fasciculation group on the scutum before joining the axon of a particular macrochaete. The positions of microchaetes on the scutum and the shape of the fasciculation groups vary between closely related species. There is no correlation between body size, bristle patterns, and fasciculation patterns. Furthermore, none of these traits correlate with the phylogenetic relationships between the species studied. We discuss the possibility that macro- and microchaetes may have different functions and that these have implications for evolutionary constraints on bristle patterns.     

Competition and coexistence in plant communities

Few ecologists today doubt that competition is an important structuring factor in plant communities, but researchers disagree on the circumstances where it is most intense, and on which traits can be considered to contribute to competitive ability in different species. The distinction between a species' effect on resources and its response to reduced resource levels might help to solve these questions. Whereas classical competition theory predicts competitive exclusion of species with similar requirements, recent ideas stress that species diversity may be explained by a multitude of processes acting at different scales, and that similarities in competitive abilities often may facilitate coexistence.     

非环境类因子对物种数目协同变化的影响

不同分类类群的物种数目常在空间上表现出显著相关地协同变化,但哪些相关系数之间存在较大的差异？究竟是什么因素导致了这种差异是值得关注的问题。从不同作者的研究方法和数据来源来看,不同研究中的研究方法、研究区域和环境条件本身就存在着差异。除以上影响因子外,我们分析了非环境类因子对物种数目协同变化的影响。结果发现分类类群间的物种数量协同变化差异明显,只有起源和生境要求相似的类群间呈显著性相关;不同鸟兽间的协同变化不存在面积效应,但是空间尺度间的相关性差异明显：物种分布型中东洋型物种的协同变化明显,而广布型和古北型不明显;在鸟类居留型中繁殖鸟与兽类的协同变化极为显著,而其他类型则不显著。综上所述,物种数量协同变化的非环境类影响因子中,生态类型和起源对分类类群间的物种数目协同关系有重要影响,     

GENETIC DISTANCE BETWEEN SPECIES PREDICTS NOVEL TRAIT EXPRESSION IN THEIR HYBRIDS

Interspecific hybridization can generate transgressive hybrid phenotypes with extreme trait values exceeding the combined range of the parental species. Such variation can enlarge the working surface for natural selection, and may facilitate the evolution of novel adaptations where ecological opportunity exists. The number of quantitative trait loci fixed for different alleles in different species should increase with time since speciation. If transgression is caused by complementary gene action or epistasis, hybrids between more distant species should be more likely to display transgressive phenotypes. To test this prediction we collected data on transgression frequency from the literature, estimated genetic distances between the hybridizing species from gene sequences, and calculated the relationship between the two using phylogenetically controlled methods. We also tested if parental phenotypic divergence affected the occurrence of transgression. We found a highly significant positive correlation between transgression frequency and genetic distance in eudicot plants explaining 43% of the variance in transgression frequency. In total, 36% of the measured traits were transgressive. The predicted effect of time since speciation on transgressive segregation was unconfounded by the potentially conflicting effects of phenotypic differentiation between species. Our analysis demonstrates that the potential impact hybridization may have on phenotypic evolution is predictable from the genetic distance between species.     

Evolutionary mechanisms in behaviour: An intraspecific genetic approach

The study of the evolutionary mechanisms in behaviour and of the biological grounds of individual variability may be based on the comparative phylogenetic approach or on an intraspecific genetic analysis. The discontinuous behavioural progression evident across species is due to the assumption that the phylogenetic “scale” may be adopted in place of the phylogenetic trees and to the fact that today's existing species have evolved in parallel and may not be used to represent an evolutionary sequence. However, despite the existence of different motor and perceptual abilities the comparative approach has shown that many analogies exist between some basic brain mechanisms across species.The existence of outstanding individual differences within the same species must be regarded as a powerful potential tool since quantitative differences between the behaviours of different individuals belonging to the same species might later result in qualitatively different phenotypes. By using different strains and mutations of mice and different genetic approaches it has been possible to assess the mode of inheritance, to calculate estimates of heritability and of the number of segregating units for different behavioural traits ranging from avoidance to maze learning and activity. The existence of clear genetic correlations between some of these behavioural patterns has also allowed the identification of some single-gene mutants affecting these traits and the characterization of a gene responsible for a major effect on activity. This psychogenetic approach shows that there are behaviour differences which are the products of evolutionary adaptive processes and that the knowledge of the genetic systems that underlie these differences is a basic step for understanding the brain mechanisms in Man.     

Plant species’ coexistence relationships may shift according to life history traits and seasons

Although several studies have demonstrated that disturbance contributes to species’ diversity, little emphasis has been placed on the identification of species’ coexistence mechanisms related to life history traits. In this study, we compared species’ richness and components of plant communities around river confluences to explore how disturbance promotes the coexistence of species with different life history traits. Sites upstream and downstream of confluences are ideal for such comparisons because they draw on the same species’ pools and have similar ambient conditions, but differ markedly in the extents of flooding disturbance. We compared sites upstream and downstream of confluences by calculating species’ richness and community similarity indices for several life history traits in both summer and spring. In summer, the combined richness of all the species, of annual- and summer-flowering species, was higher downstream from confluences than upstream, but this was not the case for perennials. Similarity analyses suggested that plant communities are constructed according to a neutral process, whereby interactions between the coexisting species are neutral. However, in spring, species’ richness was similar upstream and downstream of confluences for all life history traits. Similarity analyses suggested that under these circumstances, the communities were constructed through a species-sorting process; i.e., each life history trait had a distinct habitat preference. Thus, the relative strengths of different community assembly processes may change seasonally. We concluded that species groups differing in their responses to disturbance may coexist in a single community. Thus, community structuring following disturbance may involve two processes: a neutral and a species-sorting process. The relative importance of each may vary between species’ life history traits and between seasons, and the interaction may account for current community structures.     

Bird hosts, blood parasites and their vectors--associations uncovered by molecular analyses of blackfly blood meals

The level of host specificity of blood-sucking invertebrates may have both ecological and evolutionary implications for the parasites they are transmitting. We used blood meals from wild-caught blackflies for molecular identification of parasites and hosts to examine patterns of host specificity and how these may affect the transmission of avian blood parasites of the genus Leucocytozoon . We found that five different species of ornithophilic blackflies preferred different species of birds when taking their blood meals. Of the blackflies that contained avian blood meals, 62% were infected with Leucocytozoon parasites, consisting of 15 different parasite lineages. For the blackfly species, there was a significant association between the host width (measured as the genetic differentiation between the used hosts) and the genetic similarity of the parasites in their blood meals. The absence of similar parasite in blood meals from blackflies with different host preferences is interpreted as a result of the vector–host associations. The observed associations between blackfly species and host species are therefore likely to hinder parasites to be transmitted between different host-groups, resulting in ecologically driven associations between certain parasite lineages and hosts species.     

Persistent inter‐ and intraspecific gene exchange within a parallel radiation of caterpillar hunter beetles (Calosoma sp.) from the Galápagos

When environmental gradients are repeated on different islands within an archipelago, similar selection pressures may act within each island, resulting in the repeated occurrence of ecologically similar species on each island. The evolution of ecotypes within such radiations may either result from dispersal, that is each ecotype evolved once and dispersed to different islands where it colonized its habitat, or through repeated and parallel speciation within each island. However, it remains poorly understood how gene flow during the divergence process may shape such patterns. In the Galápagos islands, three phenotypically similar species of the beetle genus Calosoma occur at higher elevations of different islands, while lowlands are occupied by a fourth species. By genotyping all major populations within this radiation for two nuclear and three mitochondrial gene fragments and seven microsatellite markers, we found strong support that the oldest divergence separates the highland species of the oldest island from the remaining species. Despite their morphological distinctness, highland species of the remaining islands were genetically closely related to the lowland population on each island and within the same magnitude as lowland populations sampled at different islands. Repeated evolution of highland ecotypes out of the lowland species appears the most likely scenario and estimates of geneflow rates revealed extensive admixture among ecotypes within islands, as well as between islands. These findings indicate that gene exchange among the different populations and species may have shaped the phylogenetic relationships and the repeated evolution of these ecotypes.     

Co‐occurrence and phylogenetic distance in communities of mammalian ectoparasites: limiting similarity versus environmental filtering

Similarity between species plays a key role in the processes governing community assembly. The co‐occurrence of highly similar species may be unlikely if their similar needs lead to intense competition (limiting similarity). On the other hand, persistence in a particular habitat may require certain traits, such that communities end up consisting of species sharing the same traits (environmental filtering). Relatively little information exists on the relative importance of these processes in structuring parasite communities. Assuming that phylogenetic relatedness reflects ecological similarity, we tested whether the co‐occurrence of pairs of flea species (Siphonaptera) on the same host individuals was explained by the phylogenetic distance between them, among 40 different samples of mammalian hosts (rodents and shrews) from different species, areas or seasons. Our results indicate that frequency of co‐occurrence between flea species increased with decreasing phylogenetic distance between them in 37 out of 40 community samples, with 14 of these correlations being statistically significant. A meta‐analysis across all samples confirmed the overall trend for closely related species to co‐occur more frequently on the same individual hosts than expected by chance, independently of the identity of the host species or of environmental conditions. These findings suggest that competition between closely related, and therefore presumably ecologically similar, species is not important in shaping flea communities. Instead, if only fleas with certain behavioural, ecological and physiological properties can encounter and exploit a given host, and if phylogenetic relationships determine trait similarity among flea species, then a process akin to environmental filtering, or host filtering, could favour the co‐occurrence of related species on the same host.