Trade-offs between and within scales: environmental persistence and within-host fitness of avian influenza viruses

Trade-offs between different components of a pathogen''s replication and transmission cycle are thought to be common. A number of studies have identified trade-offs that emerge across scales, reflecting the tension between strategies that optimize within-host proliferation and large-scale population spread. Most of these studies are theoretical in nature, with direct experimental tests of such cross-scale trade-offs still rare. Here, we report an analysis of avian influenza A viruses across scales, focusing on the phenotype of temperature-dependent viral persistence. Taking advantage of a unique dataset that reports both environmental virus decay rates and strain-specific viral kinetics from duck challenge experiments, we show that the temperature-dependent environmental decay rate of a strain does not impact within-host virus load. Hence, for this phenotype, the scales of within-host infection dynamics and between-host environmental persistence do not seem to interact: viral fitness may be optimized on each scale without cross-scale trade-offs. Instead, we confirm the existence of a temperature-dependent persistence trade-off on a single scale, with some strains favouring environmental persistence in water at low temperatures while others reduce sensitivity to increasing temperatures. We show that this temperature-dependent trade-off is a robust phenomenon and does not depend on the details of data analysis. Our findings suggest that viruses might employ different environmental persistence strategies, which facilitates the coexistence of diverse strains in ecological niches. We conclude that a better understanding of the transmission and evolutionary dynamics of influenza A viruses probably requires empirical information regarding both within-host dynamics and environmental traits, integrated within a combined ecological and within-host framework.     

生物多样性遥感研究方法浅议

概括了遥感在生物多样性研究方面的的优势及在各种尺度为生物多样性评价提供信息的能力;讨论了生物多样性信息系统应具备的功能和应包含的内容;分析了生物多样性遥感研究中数学模型与地理信息系统的耦合问题。     

How competition affects evolutionary rescue

Populations facing novel environments can persist by adapting. In nature, the ability to adapt and persist will depend on interactions between coexisting individuals. Here we use an adaptive dynamic model to assess how the potential for evolutionary rescue is affected by intra- and interspecific competition. Intraspecific competition (negative density-dependence) lowers abundance, which decreases the supply rate of beneficial mutations, hindering evolutionary rescue. On the other hand, interspecific competition can aid evolutionary rescue when it speeds adaptation by increasing the strength of selection. Our results clarify this point and give an additional requirement: competition must increase selection pressure enough to overcome the negative effect of reduced abundance. We therefore expect evolutionary rescue to be most likely in communities which facilitate rapid niche displacement. Our model, which aligns to previous quantitative and population genetic models in the absence of competition, provides a first analysis of when competitors should help or hinder evolutionary rescue.     

生物群落的生态稳定性

1.生物群落生态稳定的概念从生态学意义看,生物群落是稳定的,就是指它在相当长的一段时间内保持其中各种群数目不变,意即一方面,任何一个种群的数量不会少到能繁衍后代,乃致绝灭,另一     

渤海线虫群落的多样性及中性模型分析

对渤海的黄河口水下三角洲、莱州湾和渤海中部共9个站位的海洋线虫群落的多样性进行了研究.用于比较的海域和站位还包括1995年胶州湾的95B2站和1988年湄州湾的A01站.以上11个站位共鉴定出自由生活海洋线虫154种,分属于107属29个科.使用种丰度(SR),香农-维弗指数(H′)和均衡度(J)用来比较不同生境的生物多样性.不同生境和站位的生物多样性水平由高到低依次为渤海中部(9761、DA18、DA19和DA20,SR=8.60±0.84,H′=4.94±0.23)、莱州湾(9762、DA2和DA4,SR=6.48士0.40,H′=3.95±3.0)和黄河口水下三角洲(E9和E11,SR=4.18±0.56,H′=3.60±0.24).线虫生物多样性与海水的盐度和沉积物的异质性指数(h)呈显著的负相关(P≤0.01).Caswell中性模型分析指明,大部分研究站位的"V"值为"-2～+2",说明未受到显著外界因子的扰动.渤海中部的9761站的"V"值为2.054,暗示环境稳定性的增强,而莱州湾的DA4站"V"值为-2.624指明受到外界环境因子的显著影响,可能与黄河口输送大量的物质有关.     

Neutral assembly of bacterial communities

Two recent, independent advances in ecology have generated interest and controversy: the development of neutral community models (NCMs) and the extension of biogeographical relationships into the microbial world. Here these two advances are linked by predicting an observed microbial taxa-volume relationship using an NCM and provide the strongest evidence so far for neutral community assembly in any group of organisms, macro or micro. Previously, NCMs have only ever been fitted using species-abundance distributions of macroorganisms at a single site or at one scale and parameter values have been calibrated on a case-by-case basis. Because NCMs predict a malleable two-parameter taxa-abundance distribution, this is a weak test of neutral community assembly and, hence, of the predictive power of NCMs. Here the two parameters of an NCM are calibrated using the taxa-abundance distribution observed in a small waterborne bacterial community housed in a bark-lined tree-hole in a beech tree. Using these parameters, unchanged, the taxa-abundance distributions and taxa-volume relationship observed in 26 other beech tree communities whose sizes span three orders of magnitude could be predicted. In doing so, a simple quantitative ecological mechanism to explain observations in microbial ecology is simultaneously offered and the predictive power of NCMs is demonstrated.     

生态学中的点格局研究概况及其在国内的应用

点格局分析是研究生态学格局的工具之一,近年来在生态学中的应用越来越多。为深入了解点格局分析方法在国内的研究与应用情况,以所总结的研究进展、一般步骤和基本要点为背景,分析评述了1996—2015年期间以点格局为主题的国内中文核心期刊文献。结果表明,在国内生态学格局研究中,应用研究占据主导地位,研究对象广泛,包括以树木为主的乔、灌、草等不同生活型的植物,甚至包括景观;基础研究,包括概括性统计量、零模型与点过程模型等方面,以及专用软件工具包的开发等研究薄弱。在应用中存在一定问题,主要表现为:概括性统计量使用单一,且以Ripley的K-函数及其变形为主;零模型(或点过程模型)是科学问题的统计表达,但是有一半以上的研究未明确给出零模型。建议在未来应用研究中重视多种统计量的组合使用和原假设的建立,在探讨热带、亚热带森林等具有复杂空间结构系统的多样性格局时,考虑对象的不同世代和系统的不同垂直层次,并加强多变量或三维概括性统计量的开发、点格局分析方法与动态过程模型的结合研究等工作。     

中国井冈山生态系统多样性

从不同尺度对井冈山生态系统进行了研究分析,并论述生态系统与生物物种多样性的关系,为井冈山生态环境保护与管理提供依据。研究发现,井冈山拥有IUCN/SSC一级生境类型9个,几乎涵盖了除海洋以外的所有生境类型,反映出井冈山生境类型非常丰富。井冈山一级生境中的面积最大的森林是井冈山自然生态系统类型及植被类型的重要基础;灌丛、草地及水域等次要的生境类型,提高了生态系统类型的复杂性和复合性。井冈山的一级生境类型是其生态系统分类的宏观基础,生境类型的丰富程度与生态系统类型的多样性密切相关。根据起源、地貌、生境和属性,以及结构和功能对井冈山生态系统类型进行逐级划分。调查发现,井冈山生态系统类型共有53类,其中自然生态系统21类(包括类型多样的森林生态系统、草地生态系统、静水生态系统等),人工生态系统14类(包括类型多样的人工湿地生态系统、人工林生态系统、农业自然复合生态系统等),复合生态系统18类(包括类型多样的人工复合生态系统、半自然复合生态系统等)。将生态系统只分到四级水平,四级以下还有丰富的生态系统类型。井冈山植物群落可分14个植被型,90个群系,180个群丛。与周围遗产地相比,井冈山的群系数量最多,与面积更大的三清山和武夷山相比,井冈山植被群系数量接近它们的3倍,表现出极其丰富的植被多样性。井冈山物种极其丰富,维管束植物和两栖动物最多,其昆虫数量仅次于武夷山,鸟类数量仅次于丹霞山。井冈山植物物种数最高。虽然井冈山总体空间(分布面积)有限,但这种分化出的丰富的生态位空间使井冈山在有限面积的植被上容纳更多的生物物种成为可能。     

Seasonal subsidy stabilizes food web dynamics: Balance in a heterogeneous landscape

Resource subsidies from external habitats can substantially affect the food web dynamics of local habitats. In this paper, we explore a mathematical model that is tailored for a stream food web, studied by Nakano and colleagues, in which consumers, in situ prey and subsidies all show seasonal fluctuation. The model reveals that the food web dynamics are stabilized if subsidies increase in summer when in situ productivity is low. Consumer dynamics are stabilized because subsidies complement seasonal resource deficiency. In situ prey dynamics are stabilized because subsidies indirectly balance the predation pressure by consumers, with seasonal change in prey carrying capacity. In summer when prey carrying capacity is low, seasonally abundant subsidies indirectly decrease predation pressure, whereas in winter, with high prey carrying capacity, scarce subsidies increase the predation pressure. Our results suggest that temporal productivity differences between spatially linked habitats are important to promote the stability of food web dynamics in a landscape context.     

中国东南部农区蚂蚁物种多样性研究

为探清我国东南部农区内蚂蚁物种多样性,本研究共设置86个采样单元格,每个单元格内选择农田、草地和人工林3种生境,每种生境设置3个重复样地,每个重复生境设置5个1 m2的重复采样样方,用吸虫器采集样方内的地表蚂蚁。结果表明：在我国东南部农区共采集鉴定地表蚂蚁30 077头,隶属于7亚科49属155种;长江中下游地区共采集蚂蚁5亚科34属93种,其中优势种3个,常见种9个,稀有种81个;华南地区采集蚂蚁7亚科42属124种,其中优势种2个,常见种11个,稀有种111个。红火蚁Solenopsis invicta Buren是华南地区个体数目最多的物种,占个体总数的39.40%;物种数目、个体密度、多样性指数和优势度指数均表现为华南地区＞长江中下游地区;不同生境内蚂蚁群落的物种数目、多样性指数和均匀度指数表现为人工林＞草地＞农田,个体密度和优势度指数人工林生境最低;两个地区3种生境蚂蚁群落间相似性系数0.2437~0.6581,处于极不相似至中等相似水平。结果表明,我国东南部农区蚂蚁种类丰富,在农区的生物多样性保护中具有重要价值;红火蚁在华南地区入侵扩散严重,亟需治理;农区内不同土地利用方式造成的生境差异影响蚂蚁群落的物种组成和多样性;不同区域、不同生境的蚂蚁群落间差异明显。     

植物群落和土壤理化性质对碧塔海湿地土壤细菌群落的影响

土壤微生物是湿地生态系统中土壤-植物系统生源要素迁移转化的引擎.探究湿地生态系统地上植物群落、土壤理化性质和空间结构与土壤细菌间的相互关系是维护湿地生态系统健康和稳定的关键.本研究运用双向指示种分析法(TWINSPAN)对碧塔海湿地采集的35个样方中的植物群落进行分类,并采用高通量测序技术对样方的表层土壤细菌进行测序,...