小型哺乳动物种群周期性波动的自我调节假说

种群调节是种群生态学的一个核心问题。文章主要阐述了小型哺乳动物种群在其低数量期自我调节的4 种可能假说和相关的实验证据。其中, 有关衰老—母体效应假说近年已受到普遍重视, 而支持多态行为假说、社会生物学假说和远交假说的证据较少, 尚需更多的实验来加以验证。衰老—母体效应假说是在应激假说的基础上发展而成的。该假说认为, 母体质量会在整个高峰期的动物中发生改变, 并能够延续到衰减期和低数量期。在低数量期, 种群内的老年个体增多, 导致它们不能维持内分泌的自稳态, 可能通过影响后代的存活和生殖而维持低数量, 进而起到调节种群周期的作用。针对国际上研究的发展趋势, 我们还对未来的研究方向提出了一些建议。     

小型哺乳动物的母体效应及其在种群调节中的作用

母体效应是指双亲的表型影响其后代表型的直接效应。它是子代对环境异质性的一种表型反应,亦是进化动力的一个重要来源,还可能与小型哺乳动物种群调节机制有关。以小型哺乳动物为例,介绍了母体效应的概念及其产生和发展过程,以及影响母体效应的营养和非营养因素,特别强调了光周期和激素的作用。在种群水平上,对度量母体效应的备选指标进行了评价,认为种群内个体的平均体重能较好地代表种群质量的高低;概述了衰老母体效应假说的主要内容及其在小型哺乳动物种群动态调节中的作用,即在种群数量的周期性波动过程中,母体质量的变化会影响后代的生殖和存活,甚至持续达2～3个世代,它与由种群年龄结构偏移所导致的衰老效应共同起作用,可使某些小型哺乳动物种群处于低数量期。本文还对母体效应的进化适应意义进行丁阐述。     

捕食风险的种群动态效应及其作用机理研究进展

捕食者不但可以通过直接捕杀猎物而控制猎物的种群数量,还可以通过捕食风险效应影响猎物种群的繁殖和动态,并且在某些情况下,捕食风险效应对猎物种群动态的控制作用甚至大于捕食者的直接捕杀.关于捕食风险效应对猎物动物繁殖产出和种群动态变化的作用及其机理方面的野外研究越来越受到国内外学者重视.本文介绍了近年来捕食风险效应的研究进展,重点关注了美国黄石国家公园中捕食者对马鹿(Cervus elephus)、加拿大育空地区的捕食者对白靴兔(Lepus americanus)的捕食风险效应等案例研究,以阐明捕食风险效应对猎物种群动态影响的重要性,以及关于捕食风险效应影响猎物种群繁殖和动态机理的两个假说(捕食者敏感食物假说、捕食应激假说).并结合我国在捕食者与猎物之间关系的研究现状,提出了进一步在野外开展捕食风险效应对濒危有蹄类猎物种群动态影响研究的建议,阐释了开展这些研究的重要意义.     

食物、捕食和种间竞争对东方田鼠种群动态的作用

采用2×2×2析因实验设计,在野外围栏条件下,测定食物、捕食和竞争物种黑线姬鼠(Apodemus agrarius)对东方田鼠(Microtus fortis)种群动态作用的格局.食物可利用性、捕食及种间竞争的独立作用对种群最小存活数均具有极显著的效应,除捕食与种间竞争的交互作用接近显著水平外,食物与种间竞争、食物与捕食者以及三者间的交互作用均不显著;三类外部因子对种群补充量的独立作用效应均达到极显著水平,且对种群补充量的作用具有累加效应;食物可利用性、捕食及种间竞争对种群繁殖成体的比例具有极显著的作用;三类外部因子对种群幼体与成体的比例具有极显著的作用.对种群年龄结构而言,与捕食者及种间竞争比较,食物可利用性是相对较弱的影响因子,在任何捕食与种间竞争交互作用条件下,食物的作用均不显著;三类外部因子均能显著地影响东方田鼠的体重增长率,但三者的交互作用对其影响不显著;MANOVA结果表明,捕食对成体存活率的作用最强烈,其次,为食物可利用性,种间竞争的作用最弱,但三者的交互作用效应不显著.对幼体的存活时间,除捕食的作用接近显著水平外,食物可利用性及种间竞争的作用均不显著.结果提供了食物可利用性、捕食和种间竞争对东方田鼠种群动态作用的充分证据,验证了食物、捕食和种间竞争对田鼠类种群动态具有独立或累加效应的总假设.     

种群外部及内部因子对东方田鼠巢区大小的效应

在野外围栏条件下, 采用重复的2×2×2析因实验, 测定外部和内部因子对东方田鼠(Microtus fortis)巢区大小的作用模式。研究结果表明, 雄体巢区大小显著大于雌体巢区大小。雄体巢区大小与体重存在显著的正相关, 而雌体巢区大小与体重的相关不显著; 雄体和雌体巢区大小与种群数量均呈显著的线性负相关。外部因子对东方田鼠雄体和雌体巢区大小的作用不一致。在排除内部因子种群数量及体重对雄体巢区大小作用的条件下, 食物对雄体巢区大小的作用显著; 而捕食及种间竞争的独立作用及其交互作用, 以及3 种外部因子的交互作用均不显著; 在排除种群数量对巢区大小作用的条件下, 食物与捕食的独立作用及3 种外部因子的交互作用对雌体巢区大小的效应均达到显著水平, 食物与种间竞争的交互作用接近显著, 而种间竞争的独立作用、食物和捕食的交互作用, 以及捕食与种间竞争的交互作用对雌体巢区大小的效应均不显著。本文结果验证了种群外部因子食物、捕食及种间竞争、种群内部因子种群数量及个体体重对田鼠种群巢区大小具有独立和交互作用的假设。     

小型哺乳动物种群调节中社会行为与亲缘结构联动机制研究进展

小型哺乳动物种群波动的内在机制备受生态学家关注。随着多态行为假说和亲缘选择理论的提出,社会行为-亲缘关系整合驱动种群波动逐渐成为小型哺乳动物种群生态学和行为生态学研究的前沿问题之一。然而,关于亲缘选择及其相关联的社会行为在种群波动中的内在联动机制研究较少,现有的理论和经验数据尚存分歧。本文简要介绍了研究亲缘关系和社会行为的新方法即社会网络分析,回顾了社会行为-亲缘结构相关理论及其亲缘效应假说,着重评述了种群调节中由物种或环境差异及熟悉性导致的社会行为与亲缘结构联动模式的不同表现,并提出未来研究应当综合考虑多个环境因子、野外调查与遗传数据相结合及考虑研究对象的个性特征。     

布氏田鼠种群内部调节的研究——种群密度、肾上腺和生殖腺重量之间的相互关系

种群动态及其调节原理是当代生态学研究中心课题之一。早期有关这方面的工作多偏重于外部调节或控制因子的研究,如注意于食物、捕食者、气候、寄生及疾病等因子的作用。自四十年代初期Elton(1942)强调了种内因子的重要性后,引起了生态学界的注意,并已围绕这方面开展了大量的工作。五十年代以来,曾由Christian (1950)、Christian etal.(1964)、Chitty(1960)、Wynne-Edwards(1964)及Krebs(1971,1974)等提出哺乳动物种群自我调节的各种假说。各自的论点虽不相同,但在某些基本思想方面却有其共同之处,即认为动物在与环境的长期适应过程中,发展了控制其数量的自我调节系统,使动物与其周围环境(包括生物、非生物)之间维持动态平衡,以利于种的生存和发展。七十年代以来,种群作为种的生存形式并对环境条件起整体反应的系统概念渗入生态学后,种群内部调节因子的作用愈益引起重视。     

球虫感染与捕食对根田鼠繁殖性能的影响

在自然界,捕食者和寄生物是两种主要的种群外部调节因子,二者的交互作用会对猎物和宿主种群波动产生深远影响。较低的球虫感染强度与捕食对根田鼠（Alexandromys oeconomus）繁殖无显著的交互作用。自然界球虫感染存在季节性变化,秋季感染强度最高。为了探究较高感染强度下,球虫与捕食对根田鼠繁殖的主效应及交互作用,本研究采用2×2析因实验设计,在野外围栏中测定了根田鼠种群肠道内寄生物的感染率和感染强度、雄性睾丸指数、睾酮水平、精子密度、精子活力以及雌性卵巢指数。结果表明,较高的感染强度下,球虫能显著抑制根田鼠的繁殖性能,但球虫感染与捕食对根田鼠的繁殖无显著的交互作用,这可能与球虫感染和捕食效应在时间上的错配有关。本研究认为,球虫感染对繁殖期小哺乳动物种群的调节作用虽有限,但其可通过与捕食者的耦合来降低宿主越冬时的存活率,进而影响宿主种群波动。     

鲁西平原黑线仓鼠种群调节机理的研究——种群密度与肾上腺、性腺重量及血浆皮质醇值之间的关系

关于种群数量波动的内在调节机制,现今已有大量的实验种群资料证明大多数小型啮齿类种群具有内部调节的反馈系统,但对自然种群的研究至今报道较少,涉及的鼠种为数不多,其中关于Christian(1964)的行为-内分泌     

灵长类营养生态学的研究进展

营养生态学是现代生态学领域研究动物食物数量和质量、营养适应以及营养对种群特征作用规律的分支学科.目前从营养生态学研究灵长类食性需求主要分为五种假说,1)能量最大化假说;2)氮(蛋白质)最大化假说;3)植物次级代谢产物调节假说;4)膳食纤维调节假说;5)食物营养均衡假说.本文从研究方法和研究内容分别介绍了这些假说在灵长类...     

Unstable dynamics and population limitation in mountain hares

The regular large-scale population fluctuations that characterize many species of northern vertebrates have fascinated ecologists since the time of Charles Elton. There is still, however, no clear consensus on what drives these fluctuations. Throughout their circumpolar distribution, mountain hares Lepus timidus show regular and at times dramatic changes in density. There are distinct differences in the nature, amplitude and periodicity of these fluctuations between regions and the reasons for these population fluctuations and the geographic differences remain largely unknown. In this review we synthesize knowledge on the factors that limit or regulate mountain hare populations across their range in an attempt to identify the drivers of unstable dynamics. Current knowledge of mountain hare population dynamics indicates that trophic interactions--either predator-prey or host-parasite--appear to be the major factor limiting populations and these interactions may contribute to the observed unstable dynamics. There is correlative and experimental evidence that some mountain hare populations in Fennoscandia are limited by predation and that predation may link hare and grouse cycles to microtine cycles. Predation is unlikely to be important in mountain hare populations in Scotland as most hares occur on sporting estates where predators are controlled, but this hypothesis remains to be experimentally tested. There is, however, emerging experimental evidence that some Scottish mountain hare populations are limited by parasites and that host-parasite interactions contribute to unstable dynamics. By contrast, there is little evidence from Fennoscandia that parasitism is of any importance to mountain hare population dynamics, although disease may cause periodic declines. Although severe weather and food limitation may interact to cause periodic high winter mortality there is little evidence that food availability limits mountain hare populations. There is a paucity of information concerning the factors limiting or regulating mountain hare populations in the Alps of Central Europe or in the tundra and taiga belts of Russia. Future research on mountain hare population dynamics should focus on the interactions between predation, parasitism and nutrition with stochastic factors such as climate and anthropogenic management including harvesting.     

Experimental tests of the role of predation in the population dynamics of voles and lemmings

• 1 Reasons for fluctuating populations of small mammals have been intensively investigated since the early days of modern ecology. Particular interest has been taken in vole populations exhibiting multiannual oscillations. Much empirical and theoretical work has been accomplished to find out the key factor(s) driving these population cycles and many reviews have been written about the results.
• 2 One of the most plausible processes for explaining regular fluctuations in small mammals is predation. Here I review the existing literature on the experimental studies of the role of predation in vole population dynamics in the hope that a critical examination of these studies will help researchers improve the design of future experiments.
• 3 Most predation manipulations have been done in exclosures, but there are also studies that have attempted to reduce or increase predator numbers in non‐fenced areas, islands and enclosures.
• 4 As the number of experimental studies has increased, their quality in terms of replication, use of controls and realistic spatial and temporal scales has also improved.
• 5 Most studies have found population‐level effects of predator manipulations on prey populations. The effects have varied from very weak to very strong, reflecting dissimilar experimental designs and the great variety of predator–prey interactions among different kinds of species in different landscapes. Most of these studies show that predation limits population growth of voles, and in some circumstances even regulate vole population fluctuations, but none of them clearly demonstrates that predation consistently changes fluctuation patterns of voles.
• 6 To be able to assess more reliably the true role of predation on (cyclic) population fluctuations of voles, more competent experiments are still needed not only over the geographical range of cyclic population dynamics, but also in areas of weakly or non‐cyclic populations of voles.

     

小型啮齿动物种群系统调节复合因子理论的野外实验研究：食物可利用性和捕食对根田鼠种群动态作用的分析

本研究在野外围栏条件下采用析因实验设计,测定营养、捕食及空间行为对根田鼠（Ｍｉ－ｃｒｏｔｕｓｏｅｃｏｎｏｍｕｓ）种群统计特征的影响。本文旨在检验下述特定假设：高质量食物可利用性和捕食对限制小型啮齿动物种群密度具有独立的和累加的效应。３年期间,４种野外实验处理６个重复的研究结果表明,附加食物并预防捕食者处理的种群具有最高密度;未附加食物及不预防捕食者处理（对照）的种群密度最低;而单一处理的种群,其密度居中。不同处理条件下,新生个体在种群的补充模式以及种群瞬时增长率的变化均与种群密度的变动相应一致。双因素ＡＮＯＶＡ的结果证明,附加高质量食物能明显地提高根田鼠的种群密度,而对种群补充量的作用则较弱,仅接近显著水平;预防捕食者不仅能显著地作用于种群密度,更能强烈地影响种群补充量。高质量食物和捕食者的作用具有累加的性质,两者的交互作用对种群密度和补充量均无显著影响。     

Specialist and generalist natural enemies as an explanation for geographical gradients in population cycles of northern herbivores

Within Fennoscandia, two well-studied groups of herbivores exhibit clear geographical gradients in their population dynamics. Populations of a forest lepidopteran ( Epirrita autumnata , the autumnal moth) and voles of the genera Microtus and Clethrionomys show pronounced multi-annual cycles in the north but become more stable towards the south. Here we review empirical and theoretical studies on these species, mainly regarding the biological mechanisms that are assumed to generate the pattern of population dynamics in both systems. We conclude that the specialist/generalist predation hypothesis offers a common explanation for the population cycles and their geographical gradients irrespective of whether a herbivorous insect or small mammals are concerned. According to this hypothesis, originally developed for the Fennoscandian voles, but now applied also to E. autumnata , population cycles are generated by specialist natural enemies (predators for the voles and parasitoids for E. autumnata ). Furthermore, the dynamic shift from cycles to stability is assumed to be caused by an increase in the density and diversity of generalist natural enemies from north to south in Fennoscandia.     

Population cycles in voles and lemmings: state of the science and future directions

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Experimental tests of predation and food hypotheses for population cycles of voles

Pronounced population cycles are characteristic of many herbivorous small mammals in northern latitudes. Although delayed density-dependent effects of predation and food shortage are often proposed as factors driving population cycles, firm evidence for causality is rare because sufficiently replicated, large-scale field experiments are lacking. We conducted two experiments on Microtus voles in four large predator-proof enclosures and four unfenced control areas in western Finland. Predator exclusion induced rapid population growth and increased the peak abundance of voles over 20-fold until the enclosed populations crashed during the second winter due to food shortage. Thereafter, voles introduced to enclosures which had suffered heavy grazing increased to higher densities than voles in previously ungrazed control areas which were exposed to predators. We concluded that predation inhibits an increase in vole populations until predation pressure declines, thus maintaining the low phase of the cycle, but also that population cycles in voles are not primarily driven by plant-herbivore interactions.     

From arctic lemmings to adaptive dynamics: Charles Elton's legacy in population ecology

We shall examine the impact of Charles S. Elton's 1924 article on periodic fluctuations in animal populations on the development of modern population ecology. We argue that his impact has been substantial and that during the past 75 years of research on multi-annual periodic fluctuations in numbers of voles, lemmings, hares, lynx and game animals he has contributed much to the contemporary understanding of the causes and consequences of population regulation. Elton was convinced that the cause of the regular fluctuations was climatic variation. To support this conclusion, he examined long-term population data then available. Despite his firm belief in a climatic cause of the self-repeating periodic dynamics which many species display, Elton was insightful and far-sighted enough to outline many of the other hypotheses since put forward as an explanation for the enigmatic long-term dynamics of some animal populations. An interesting, but largely neglected aspect in Elton's paper is that it ends with speculation regarding the evolutionary consequences of periodic population fluctuations. The modern understanding of these issues will also be scrutinised here. In population ecology, Elton's 1924 paper has spawned a whole industry of research on populations displaying multi-annual periodicity. Despite the efforts of numerous research teams and individuals focusing on the origins of multi-annual population cycles, and despite the early availability of different explanatory hypotheses, we are still lacking rigorous tests of some of these hypotheses and, consequently, a consensus of the causes of periodic fluctuations in animal populations. Although Elton would have been happy to see so much effort spent on cyclic populations, we also argue that it is unfortunate if this focus on a special case of population dynamics should distract our attention from more general problems in population and community dynamics.     

Population dynamics of large and small mammals

We offer an evaluation of the Caughley and Krebs hypothesis that small mammals are more likely than large mammals to possess intrinsic population regulating mechanisms. Based on the assumption that intrinsic regulation will be manifest via direct density-dependent feedbacks, and extrinsic regulation via delayed density-dependent feedbacks, we fit autoregressive models to 30 time series of abundance for large and small mammals to characterize their dynamics. Delayed feedbacks characterizing extrinsic mechanisms, such as trophic-level interactions, were detected in most time series, including both small and large mammals. Spectral analyses indicated that the effect of such delayed feedbacks on the variability in population growth rates differed with body size, with large mammals exhibiting predominantly reddened and whitened spectra in contrast with predominantly blue spectra for small mammals. Large mammals showed less variance and more stable dynamics than small mammals, consistent with, among other factors, differences in their potential population growth rates. Patterns of population dynamics in small versus large mammals contradicted those predicted by the Caughley and Krebs hypothesis.