幂指模型在害虫密度与作物产量损失研究中的应用

本文首次引入幂指模型 ( y=y L Mexp( - bda) )来模拟害虫密度与作物产量间的关系 ,通过对 15组不同来源的害虫与作物竞争资料的模拟 ,证明幂指模型具有实际的生物学意义 ,能准确地描述多种害虫和多种作物间的危害关系 ,预测害虫危害作物可能造成的产量损失。为害虫的经济防治提供了一种新的研究方法     

三江平原不同强度干扰下湿地植物群落的物种组成和多样性变化

以三江平原湿地-农田景观中沟渠的密度作为反映干扰强度的指标,研究了不同沟渠密度下湿地斑块植物群落的物种组成和多样性变化.结果表明:(1)在不同的干扰强度下,湿地植物群落的物种组成差异很大, 随干扰强度增大,原有湿生物种减少,而中湿生、中生物种显著增加;(2)湿地植物群落的多样性随干扰强度的增大,整体上呈降低趋势,群落多样性在中等沟渠密度下(0.6～1.2km/km2)达到最大,但不同沟渠密度下群落间多样性差异基本不显著;(3)位点间的干扰强度差异越大,Whittaker指数值越高;(4)不同的干扰强度下,各湿地斑块内部的物种周转速率同样在沟渠密度中等(0.6～1.2km/km2)时最高.     

害虫密度与作物产量损失预测的一种新方法

本文首次引入幂指模型（y=yLMexp(-bd^α）来模拟害虫密度与作物产量间的关系。通过对15组不同来源的害虫与作物竞争资料的模拟,证明幂指模型具有实际性的生物学意义,能准确地描述多种害虫和多种作物间的危害关系,预测害虫危害作物可能造成的产量损失,为害虫的经济防治提供了一种新的研究方法。     

一类具有非线性密度制约的食饵-捕食者扩散模型的稳定性

讨论了一类具有非线性密度制约的食饵-捕食者扩散规模型,运用线性化方法和Lyapunov函数法分别讨论该反应扩散模型唯一正平衡点的局部渐近稳定性和全局渐近稳定性.     

种内及种间干扰对围栏内花鼠分散贮藏行为的影响

2009 年9 月在黑龙江省带岭区东方红林场10 m ×10 m 半天然围栏内模拟花鼠种内(不同性别) 和种间
(大林姬鼠) 干扰竞争对花鼠分散埋藏红松种子行为的影响。实验分四个处理两个批次进行,依次为单只花鼠对
照实验(雄性7 只,雌性9 只)、种内同性干扰竞争、种内异性干扰竞争和种间干扰竞争。结果表明:(1)花鼠
雌性个体的分散埋藏强度明显高于雄性个体;(2)种间干扰竞争引起花鼠对红松分散埋藏比例明显增加,而种
内干扰对花鼠分散埋藏行为的影响不显著;(3) 种内干扰竞争条件下,同性干扰竞争和异性干扰竞争对花鼠分
散埋藏行为均无显著影响;(4)雄性个体在同性干扰下,埋藏强度不变;而在雌性个体干扰竞争下,埋藏强度
增加;(5)雌性个体在雌性和雄性干扰条件下,花鼠分散埋藏行为均无明显变化。     

一类扩散的种内相食系统正平衡态的全局渐近稳定性

讨论一类扩散的种内相食的捕食者-食饵模型,该模型带有齐次Neumann边界条件.通过迭代的方法证明:在适当的条件下,该模型唯一正常数平衡解全局渐近稳定.     

多物种共存系统中3种蜘蛛对褐飞虱的控制作用

选择稻田生态系统中天敌蜘蛛优势种食虫沟瘤蛛（Oedothorox insecticeps)、拟水狼蛛（Pirata subpiraticus)、粽管巢蛛（Clubiona japonicola)和水稻主要害虫飞虱（Nilaparvata lugenis)组成多物种共存系统,运用二次通用旋转组合设计统计方法探讨多种蜘蛛对1种稻虫的控制作用,分析天敌之间以及天敌与害虫之间的相互作用关系,得出了天敌对害虫的捕食量模型2个。对模型进行主次分析表明,害虫自身密度的大小对天敌的捕食量影响较大。天敌中对捕食量作用最大的是粽管巢蛛,其次是拟水狼蛛,食虫沟瘤蛛的作用稍小。分析天敌间的交互作用表明,天敌个体大、活动能力强、生态位窄及其重叠值高、捕食量大,它们的种内种间干扰程度也大,特别是粽管巢蛛的种内干扰、拟水狼蛛和粽管巢蛛的种间干扰作用十分明显。最后讨论了天敌蜘蛛能有效控制害虫的最大密度,以及在该害虫密度下各种天敌密度的最佳组合。     

叉角厉蝽对斜纹夜蛾的捕食功能反应

叉角厉蝽Cahtheconidea furcellata是一种重要的捕食性天敌昆虫,为了探明该虫的捕食潜能,在室内条件下研究了叉角厉蝽成虫对斜纹夜蛾Spodoptera litura Fab.二龄和三龄幼虫的捕食作用和种内干扰作用。结果表明,叉角厉蝽成虫的捕食量随着斜纹夜蛾幼虫的密度增加而增大,其捕食功能反应符合HollingⅡ型方程。叉角厉蝽对斜纹夜蛾2龄幼虫的捕食量符合Na=0.7364N/(1+0.0118N),对斜纹夜蛾3龄幼虫的捕食量符合Na=0.7504N/(1+0.0005N),叉角厉蝽的捕食作用有较强的种内干扰反应,捕食率与个体间相互干扰的关系符合Hassell模型。叉角厉蝽的捕食量与害虫密度正相关,寻找效应与害虫密度负相关。     

皖南凹耳臭蛙地理分布格局与生境选择

凹耳臭蛙(Odorrana tormota)是一种小型山溪蛙类,由于叫声独特,种内具有超声通讯功能而引起国内外相关专家的广泛关注。首次针对皖南凹耳臭蛙地理分布、生境选择以及人为干扰强度对种群密度的影响进行了研究。共调查了9县1区32条不同的山溪,发现其中的16个有凹耳臭蛙分布,除黄山区的香溪和浮溪具文献记录外,其余14个分布点均为首次报道。基于现存凹耳臭蛙分布点的水系关系,推测该物种在皖南的分布呈现出以青弋江、新安江和水阳江三大水系为纽带、间断分布的格局。对其中10个分布点222只凹耳臭蛙生境选择的统计结果表明,在夜晚活动周期内,该物种对乔木、灌木丛、草本植物、岩石、沙滩和倒伏朽木等不同生境的选择具有显著差异(F5,54=25.75,P0.001),栖息在草本植物和灌丛中蛙的数量明显多于栖息在其它几种生境类型中的蛙类。暗示溪流沿岸的草本植物和灌丛对该物种的生存和繁衍具有重要意义,乔木对其非活动周期的隐蔽可能具有不可替代的作用。根据人类活动对其栖息地破坏程度,将人为干扰程度划分为强、中和弱3种不同强度,对不同干扰强度下种群相对密度进行单因素方差分析。结果表明,中等干扰强度下的种群密度显著高于其它两种强度下的种群密度(F2,13=8.155,P=0.005)。推测适度的人为干扰可能增加了栖息地内昆虫的种类和数量,对蛙类的生存和繁衍更为有利。但随着人为干扰强度的增强,对溪流沿岸植被的破坏更为剧烈,种群密度显著下降。     

具有非线性种内制约关系和分布时滞竞争模型的稳定性

构造并研究了一类具有分布时滞和非线性种内制约关系的竞争模型.得到了这类模型的边界平衡点和共存平衡点全局渐近稳定的条件,以及分布时滞、非线性种内制约关系对模型的影响.     

Mechanisms behind positive diversity effects on ecosystem functioning: testing the facilitation and interference hypotheses

Little is known about the mechanisms behind positive effects of species richness on ecosystem functioning. In a previous study that showed a positive effect of aquatic detritivore species richness on leaf litter breakdown (process) rates, we proposed that facilitation and release from intra-specific interference were the two most likely mechanisms. To test the interference hypothesis, we performed an experiment using three densities of each of three detritivore species and found varying effects on leaf breakdown rates across species: one species showed no effect, one a positive, marginally insignificant, effect, and a third species showed a significant, positive effect of decreasing density. The density (interference) effect thus partly explained the results from our previous study. The facilitation hypothesis was tested by sequentially introducing and removing two species. We predicted that, if this hypothesis were true, facilitation would be expressed in higher process rates than when replacing with individuals of the same species. We found that process rate per unit biomass did increase when one species was introduced after the other species, while the opposite sequence did not show any increase. Hence, this result was also confirmative of our previous results. Therefore, we conclude that both intra-specific interference and inter-specific facilitation may explain the positive effect of species richness observed in our system. Since many species exhibit intra-specific interference that inhibits foraging efficiency, this may be a general mechanism generating effects of species richness per se. If facilitation is unidirectional, or if it involves few species, it is more likely to be species specific with species identities being more important than species richness per se. We conclude that species loss may be expected to have negative consequences on ecosystem functioning if anyspecies is lost, with additional effects in the event of losing "facilitator" species.     

Density-dependence in single-species populations of plants

The general form of yield-density relationships in plant populations is discussed with reference to reciprocal equations and the $\text{3}\text{2}$ power law, which describes the concomitant changes in plant weight and density during self-thinning. A model to describe the pattern of mortality in high density populations is also discussed with particular reference to the nature of intraspecific competition within plant populations.A reparameterized version of a reciprocal equation proposed by Bleasdale & Nelder is used to describe the relationship between individual plant weight and surviving plant density. The biological interpretation of the parameters is discussed in relation to the dry matter production of isolated plants, the density at which mutual interference between neighbours becomes appreciable, and the efficiency of resource utilization at high densities.The reparameterized equation is then used together with an equation which describes mortality during self-thinning as the basis for a new model to describe the relation between total plant yield and sowing density. The law of allometry is used in conjunction with the model to describe the relationship between the weight of a plant part and density, and this then forms the basis for a model of the population dynamics of annual plants with effectively discrete generations. Finally the dynamical behaviour of plant populations is discussed. It is concluded that most plant populations will show neighbourhood stability with exponential or perhaps oscillatory damping towards an equilibrium.     

A Dynamic Equation for Plant Interaction and Application to Yield-density-time Relations

A model for plant interaction is developed based on a definitionof space in terms of actual and potential amount of growth factorsabsorbed per unit of time. The resulting equation is a second-orderdifferential equation which is solved by dynamic simulation.Five data sets on yield-density relations are used to demonstratethe model's excellent predictive power. Competition model, plant interaction, yield-density relations, Richards function, subterranean clover (Trifolium subterraneum L.), Wimmera ryegrass (Lolium loliaceum Hand-Mazz.), lettuce (Lactuca sativa L.), maize (Zea mays L.), lucerne (Medicago sativa L     

Genetic tagging: contemporary molecular ecology

Population genetic analyses have been highly successful in deciphering inter- and intra-specific evolutionary relationships, levels of gene flow, genetic divergence and effective population sizes. Parameters estimated by traditional population genetic analyses are evolutionary averages and thus not necessarily relevant for contemporary ecological or conservation issues. Molecular data can, however, also provide insight into contemporary patterns of divergence, population size and gene flow when a sufficient number of variable loci are analysed to focus subsequent data analyses on individuals rather than populations. Genetic tagging of individuals is an example of such individual-based approaches and recent studies have shown it to be a viable alternative to traditional tagging methods. Owing to the ubiquitous presence of hyper-variable DNA sequences in eukaryote genomes it is in principle possible to tag any eukaryote species and the required DNA can be obtained indirectly from substrates such as faeces, sloughed skin and hair. The purpose of this paper is to present the concept of genetic tagging and to further advocate the extension of individual-based genetic analyses beyond the identification of individuals to other kinds of relationships, such as parent-offspring relations, which more fully exploit the genetic nature of the data.     

The iterated continuous prisoner's dilemma game cannot explain the evolution of interspecific mutualism in unstructured populations

The evolutionionary origin of inter- and intra-specific cooperation among non-related individuals has been a great challenge for biologists for decades. Recently, the continuous prisoner's dilemma game has been introduced to study this problem. In function of previous payoffs, individuals can change their cooperative investment iteratively in this model system. Killingback and Doebeli (Am. Nat. 160 (2002) 421-438) have shown analytically that intra-specific cooperation can emerge in this model system from originally non-cooperating individuals living in a non-structured population. However, it is also known from an earlier numerical work that inter-specific cooperation (mutualism) cannot evolve in a very similar model. The only difference here is that cooperation occurs among individuals of different species. Based on the model framework used by Killingback and Doebeli (2002), this Note proves analytically that mutualism indeed cannot emerge in this model system. Since numerical results have revealed that mutualism can evolve in this model system if individuals interact in a spatially structured manner, our work emphasizes indirectly the role of spatial structure of populations in the origin of mutualism.     

Quantifying the community-level consequences of competition

Changes in plant community structure after changes in some aspect of the environment such as nutrients or grazing is often ascribed to changes in competitive relationships among the plants. However, very rarely is competition measured directly in such experiments. To distinguish between the direct effects of environmental treatments and changes in competitive relationships, it is necessary to quantify the influence of competition on community structure and compare the magnitude and direction of this influence between environments. We describe an experimental approach to accomplish this that is based on the classic yield-density experiment of agronomy. The approach is called the community-density experiment and requires experimental establishment of a gradient in total initial community density such that absolute densities of each species increase but initial relative abundances of each species stay constant along the gradient. We define various indices of the magnitude of community-level consequences of increasing density that can be compared among environments such as different fertilizer or grazing treatments. We also discuss various practical ways of achieving the experimental density gradient that are suitable for different kinds of communities. *** DIRECT SUPPORT *** A02DO006 00011     

Modeling nucleotide evolution at the mesoscale: the phylogeny of the neotropical pitvipers of the Porthidium group (viperidae: crotalinae)

We analyzed the phylogeny of the Neotropical pitvipers within the Porthidium group (including intra-specific through inter-generic relationships) using 1.4 kb of DNA sequences from two mitochondrial protein-coding genes (ND4 and cyt-b). We investigated how Bayesian Markov chain Monte-Carlo (MCMC) phylogenetic hypotheses based on this 'mesoscale' dataset were affected by analysis under various complex models of nucleotide evolution that partition models across the dataset. We develop an approach, employing three statistics (Akaike weights, Bayes factors, and relative Bayes factors), for examining the performance of complex models in order to identify the best-fit model for data analysis. Our results suggest that: (1) model choice may have important practical effects on phylogenetic conclusions even for mesoscale datasets, (2) the use of a complex partitioned model did not produce widespread increases or decreases in nodal posterior probability support, and (3) most differences in resolution resulting from model choice were concentrated at deeper nodes. Our phylogenetic estimates of relationships among members of the Porthidium group (genera: Atropoides, Cerrophidion, and Porthidium) resolve the monophyly of the three genera. Bayesian MCMC results suggest that Cerrophidion and Porthidium form a clade that is the sister taxon to Atropoides. In addition to resolving the intra-specific relationships among a majority of Porthidium group taxa, our results highlight phylogeographic patterns across Middle and South America and suggest that each of the three genera may harbor undescribed species diversity.     

How many eggs should be laid in one's own nest and others’ in intra-specific brood parasitism?

Recent field studies have demonstrated that many bird species practice intra-specific brood parasitism. They lay eggs in the nests of other individuals of the same species, let the foster parents rear their offspring and avoid the cost of parental care. It has been shown that many birds, including starlings, swallows and geese, practice intra-specific brood parasitism in various forms. Intra-specific brood parasitism can be viewed in terms of optimal resource allocation: how many eggs should be put in the nests of other individuals under the risk of being parasitized by others. The situation here is a game, because the fitness of a parasitic individual depends on how other individuals behave (how many individuals practice parasitism and to what extent). The ecology of intra-specific brood parasitism has been investigated extensively by field ornithologists recently and it is full of material for modeling population/evolutionary biology. In this paper, I present a simple individual-based model to challenge the resource allocation problem in intra-specific brood parasitism. Previous theoretical studies of intra-specific brood parasitism have been based on ESS or quantitative genetics models, where a population is implicitly assumed to be homogeneous and the distribution form of the trait being studied (the allocation rate or the number of eggs laid parasitically) is inherently monomorphic. This paper aims to explore the evolution of intra-specific brood parasitism without these restrictions. In the model, an individual is assigned a strategy, an allocation ratio of eggs that are laid parasitically in the nests of other individuals, and the strategy is inherited by offspring either asexually or sexually. Based on the simulation analysis, the evolution of the allocation rate (the extent of intra-specific brood parasitism) is discussed. The extension of this model to a tractable analytical model is also discussed.     

Lifecycle closure, lineage sorting, and hybridization revealed in a phylogenetic analysis of European oak gallwasps (Hymenoptera: Cynipidae: Cynipini) using mitochondrial sequence data

Oak gallwasps are cyclically parthenogenetic insects that induce a wide diversity of highly complex species- and generation-specific galls on oaks and other Fagaceae. Phylogenetic relationships within oak gallwasps remain to be established, while sexual and parthenogenetic generations of many species remain unpaired. Previous work on oak gallwasps has revealed substantial intra-specific variation, particularly between regions known to represent discrete Pleistocene glacial refuges. Here we use statistical phylogenetic inference methods on sequence data for a fragment of the mitochondrial cytochrome b gene to reconstruct the relationships among 62 oak gallwasp species. For 16 of these we also include 23 additional cytochrome b haplotype sequences from different Pleistocene refuge areas to test the effect of intra-specific variation on inter-specific phylogeny reconstruction. The reconstructed phylogenies show good intra-generic resolution and identify several conserved clades, but fail to reconstruct either very recent or very ancient divergences. Nine of the 16 species represented by multiple haplotypes are not monophyletic. The apparent discordance between the recovered gene tree and the current taxonomic classification can be explained through: (a) collapsing of some species currently known only from either a sexual or a parthenogenetic generation into a single cyclically parthenogenetic entity; (b) sorting of ancestral polymorphism in diverging lineages, and (c) horizontal transfer of haplotypes, perhaps due to hybridization within glacial refuges. Our conclusions emphasise the need for careful intra-specific sampling when reconstructing phylogenies for radiations of closely related species and imply that for certain taxonomic groups full phylogenetic resolution (using molecular markers) may not be attainable.     

Gene duplication as a major force in evolution

Gene duplication is an important mechanism for acquiring new genes and creating genetic novelty in organisms. Many new gene functions have evolved through gene duplication and it has contributed tremendously to the evolution of developmental programmes in various organisms. Gene duplication can result from unequal crossing over, retroposition or chromosomal (or genome) duplication. Understanding the mechanisms that generate duplicate gene copies and the subsequent dynamics among gene duplicates is vital because these investigations shed light on localized and genomewide aspects of evolutionary forces shaping intra-specific and inter-specific genome contents, evolutionary relationships, and interactions. Based on whole-genome analysis of Arabidopsis thaliana, there is compelling evidence that angiosperms underwent two whole-genome duplication events early during their evolutionary history. Recent studies have shown that these events were crucial for creation of many important developmental and regulatory genes found in extant angiosperm genomes. Recent studies also provide strong indications that even yeast (Saccharomyces cerevisiae), with its compact genome, is in fact an ancient tetraploid. Gene duplication can provide new genetic material for mutation, drift and selection to act upon, the result of which is specialized or new gene functions. Without gene duplication the plasticity of a genome or species in adapting to changing environments would be severely limited. Whether a duplicate is retained depends upon its function, its mode of duplication, (i.e. whether it was duplicated during a whole-genome duplication event), the species in which it occurs, and its expression rate. The exaptation of preexisting secondary functions is an important feature in gene evolution, just as it is in morphological evolution.