混沌在种群动态中的应用

通过对种群数量变化模型和空间格局的分析，结合不稳定系统动力学的混沌现象，对种群动态中存在的混沌进行了粗略的探讨．认为CSR三角形中的S-对策者具有混沌的特点．由于生态场中因子具有混沌性质，及其相互作用过程中的不稳定系统动力学的影响，种群也具有混沌特点．     

一种用粪便样方法估计林麝种群密度的新方法

数量(密度)特征是动物种群的一个重要特征，是定点研究一个野生种群生态的一项非常重要的基础工作．其数量和年龄结构为进一步分析其种群的密度、移动、巢域和核域，尤其是为种群动态提供依据，也是珍稀动物保护和资源动物管理利用的先行工作和重要组成部份．关于野生动物种群数量的具体统计方法，有不少的文章报道，然而从动物的空间分布格局来研究大型脊椎动物却较为少见，这主要是受研究方法的限制．为此，作者对此进行了改进，提出了一种新的研究方法：临时空间样方法，并将其应用到冶勒自然保护区林麝的数量调查研究中去．结果表明：(1)集聚分布指数CA=12．09，说明冶勒自然保护区的林麝有较高的集聚度；(2)林麝粪堆在野外的分布属于聚集分布，并与负二项分布拟合较好；(3)在冶勒自然保护区，生活有62～98只左右的林麝，其密度为：1．0～1．6只／km^2．林麝在冶勒自然保护区呈现聚积分布的原因是由于环境和人类活动因素造成的．图1表2参24     

岷江上游林草交错带祁连山圆柏群落的物种多样性及乔木种群的分布格局

应用5种多样性指数对祁连山圆柏群落的物种多样性进行了研究，并采用相邻格子样方法测定了乔木种群及其各立木级的分布格局．结果表明，灌木层的物种多样性偏低，而草本层多样性较高，群落总的物种多样性(以丰富度表示)较高．群落总的物种多样性较高是由于较低的灌木层多样性与较高的草本层多样性综合作用的结果，与放牧影响、阳坡的干燥环境有关，可能是林草交错区固有的特点．乔木种群的分布格局呈现出集群分布，但在其发育过程中显示了动态变化的特征，即在幼苗和小树阶段为集群分布，到了大树阶段转变为随机分布或均匀分布．表6参32     

物种灭绝的若干种可能的序

利用集合种群共存动力模式，研究了由于栖息地毁坏而导致物种灭绝的顺序问题．研究结果表明：在群落里各物种种群具有相等的死亡率的假设下，栖息地毁坏而导致物种的灭绝存在3种最基本可能的顺序，既最弱物种与最强物种相伴灭绝，最强物种与最弱物种是强弱交替灭绝，以及由强而弱依次灭绝．参7     

安徽省宣州扬子鳄饲养种群繁殖现状分析

对１９９３ ～１９９８ 年安徽省扬子鳄繁殖研究中心内的亲代与子代鳄的繁殖情况进行了统计研究,结果表明：扬子鳄亲代卵的平均受精率为（７５．６６±２．２９） ％ ,子一代为（６９ ．２４ ±５ ．１２） ％ ,经ｔ 检验,两者差异显著;亲代产卵孵化幼鳄的平均畸形率为（０．３０ ±０．２０） ％ ,而子一代产卵幼鳄平均畸形率为（１ ．８５±０．９５） ％ ,经ｔ 检验,两者差异显著．但受精卵幼鳄孵化率在两代间差异不显著．通过饲养种群的家系和有效群体大小分析,作者认为造成子代鳄的繁殖率下降和畸形率上升的原因与近亲繁殖有关．对扬子鳄的遗传保护研究提出了建议．     

对种群增长模型的改进

提出有限空间种群增长的Logistic新模型即ds(dt)^-1=rs(1-ds^0／k)，其中参数d描述环境对种群增长的影响，参数θ为种内竞争特性参数．该模型通过种群的竞争特性因子θ控制，将指数增长、线性制约、下凹增长和上凸增长非线性制约概括为一个统一的自适应的非线性制约模型．以格氏栲、红锥种群基面积增长为例，运用遗传算法对不同种群增长模型进行最优拟合与比较分析，表明新模型能较好地描述格氏栲、红锥种群增长规律，为种群增长动态变化的一个理想的机理描述式．表4参14     

濒危植物矮牡丹种群生物量的研究

对矮牡丹种群生物量的研究表明，矮牡丹地上无性小株的叶、茎干和根系的生物量可分别用m1（DW）＝－0．232＋000771A，ms（DW）＝0．370＋0．18000（D2H1），mr（DW）＝1．54＋0．000338（AH1）来表示象矮牡丹这种似棕榈型生长型的小灌木，植冠面积容易测得，用植冠面积进行叶重的模拟最为准确随年龄的增长，矮牡丹种群各部分生物量都呈指数模式增长     

塔玛亚历山大藻对褶皱臂尾轮虫实验种群动态的影响

采用单个体培养方法研究有毒赤潮藻塔玛亚历山大藻（Alexandrium tamarense）的细胞再悬浮液、细胞破碎液及其与亚心形扁藻（Platymonas subcordiformis）的混合藻液对褶皱臂尾轮虫（Brachionus plicatilis）实验种群动态的影响．结果表明，塔玛亚历山大藻及其细胞破碎液延缓了褶皱臂尾轮虫的生长发育，使轮虫的生殖前期延长，生殖期及寿命缩短，特定年龄出生率降低，产卵量减少，从而导致轮虫生殖力下降，种群增长受阻．其中以塔玛亚历山大藻细胞再悬浮液对轮虫的影响最为显著，rm仅为0．1832d^-1，图1表2参18     

植物区系学中特有现象的研究进展(Ⅰ)--概念、类型、起源及其研究意义

植物区系学中的特有现象是其研究的重点内容，对特有现象的概念、类型、起源及其研究意义作了详细的论述；其次，总结了中国植物区系的基本情况、生活型、分布区学、水平分布、垂直分布与起源等研究成果；第三，介绍了研究特有现象的形态-地理学方法、细胞地理学方法和等位酶分析方法；第四，指出了中国植物区系中特有现象研究所面临的困境，认为应该集中力量重点研究滇黔桂、横断山脉以及华中等3个地区的植物区系基本特征、组成、起源、演化与扩散等内容．     

中国穿山甲受危状况评估

中国穿山甲主要分布在我国长江以南地区，少量分布在与我国广西、云南接壤的国家．分析了中国穿山甲(Manis pentadactyla)的各种致危因素共19种，并以此评估了它的受危状况．结果表明，中国穿山甲属易受危物种，潜在的绝灭危险较大．较高的受危指数(Ti=0．6947)表明它处于高度受危状态，已成为濒危物种(En)．最关键的外在致危因素是过度狩猎、利用和走私，其次是栖息地的丧失、改变、岛屿化和种群分布格局的片断化．上世纪60年代后至今，估计中国穿山甲种群数量已下降了88．88％～94．12％，栖息地内的种群密度已低至0．001134～0．056头／km^2，较高的狩猎压力以及栖息地的丧失、改变、岛屿化和走私还将持续，受危程度将进一步加重，潜在的绝灭危险继续上升．要缓解中国穿山甲当前的受危状况，减轻狩猎压力，保护好现有栖息地，打击走私是当务之急．依据IUCN红色名录(Red List，version3．1)和我国濒危动物红皮书对受危物种等级标准的定义，以及CITES附录物种等级标准、我国重点保护动物等级标准，中国穿山甲应当从我国濒危动物红皮书中的易危级(Vu)和IUCN红色名录里的低危接近易危(LR／nt)上调为濒危级(En)，由CITES附录Ⅱ上升为附录Ⅰ，由国家Ⅱ级保护动物上升为Ⅰ级保护．图3表1参40     

Epidemic Disease and the Catastrophic Decline of Australian Rain Forest Frogs

In the montane rain forests of eastern Australia at least 14 species of endemic, stream-dwelling frogs have disappeared or declined sharply (by more than 90%) during the past 15 years. We review available information on these declines and present eight lines of evidence that collectively suggest that a rapidly spreading, epidemic disease is the most likely responsible agent. The extreme virulence of the putative frog patbogen suggests it is likely exotic to Australian rain forests. We propose that exotic pathogens may be responsible for some recent declines of amphibian populations on other continents and that the intercontinental spread of such pathogens is greatly facilitated by human activities such as the thriving international trade in aquarium fish. Our hypothesis may help explain why some amphibian populations in seemingly pristine environments have mysteriously declined.     

Amphibian Declines: Judging Stability, Persistence, and Susceptibility of Populations to Local and Global Extinctions

Extinctions are normal biological phenomena. Both mass extinctions in geological time and local extinctions in ecological time are well documented, but rates of extinction have increased in recent years—especially in vertebrates, including amphibians—as illustrated by recent reports of their population declines and range reductions. We suggest that long-term population data are necessary for rigorously evaluating the significance of the amphibian declines. Due to the physiological constraints, relatively low mobility, and site fidelity of amphibians, we suggest that many amphibian populations may be unable to recolonize areas after local extinction.     

Inconclusiveness of Chytridiomycosis as the Agent in Widespread Frog Declines

Abstract:  Although there is considerable evidence to support the hypothesis that the chytrid fungus Batrachochytrium dendrobatidis is the primary agent responsible for widespread declines in amphibian populations, particularly rainforest frog populations in Australia and Central America, I argue the case has not yet been made conclusively. Few specimens were collected at the time of population declines, so it may never be possible to conclusively determine their cause. It remains unclear whether the pathogen is novel where declines have occurred. Although it is not necessary that the infection be novel for it to be implicated in declines, if a preexisting pathogen has only recently caused extinctions, cofactors must be important. Whether the pattern of outbreaks represents a "wave" of extinctions is unclear, but if it does, the rate of spread in Australia is implausibly high for a waterborne pathogen, given the most likely estimates of epidemiological parameters. Although B. dendrobatidis is an amphibian pathogen according to Koch's postulates, the postulates are neither necessary nor sufficient criteria to identify a pathogen. The following key pieces of information are necessary to better understand the impact of this fungus on frog communities: better knowledge of the means and rate of transmission under field conditions, prevalence of infection among frog populations, as distinct from morbid individuals, and the effect of the fungus on frogs in the wild. It is crucial to determine whether there are strains of the fungus with differing pathogenicity to particular frog species and whether host-pathogen coevolution has occurred or is occurring. Recently developed diagnostic tools bring into reach the possibility of addressing these questions and thus developing appropriate strategies to manage frog communities that may be affected by this fungus.     

Citation Rate and Perceived Subject Bias in the Amphibian‐Decline Literature

Abstract: As a result of global declines in amphibian populations, interest in the conservation of amphibians has grown. This growth has been fueled partially by the recent discovery of other potential causes of declines, including chytridiomycosis (the amphibian chytrid, an infectious disease) and climate change. It has been proposed that researchers have shifted their focus to these novel stressors and that other threats to amphibians, such as habitat loss, are not being studied in proportion to their potential effects. We tested the validity of this proposal by reviewing the literature on amphibian declines, categorizing the primary topic of articles within this literature (e.g., habitat loss or UV‐B radiation) and comparing citation rates among articles on these topics and impact factors of journals in which the articles were published. From 1990 to 2009, the proportion of papers on habitat loss remained fairly constant, and although the number of papers on chytridiomycosis increased after the disease was described in 1998, the number of published papers on amphibian declines also increased. Nevertheless, papers on chytridiomycosis were more highly cited than papers not on chytridiomycosis and were published in journals with higher impact factors on average, which may indicate this research topic is more popular in the literature. Our results were not consistent with a shift in the research agenda on amphibians. We believe the perception of such a shift has been supported by the higher citation rates of papers on chytridiomycosis.     

Hypothesis Concerning the Causes of the Disappearance of Boreal Toads from the Mountains of Colorado

Recent reports of world-wide declines and extinctions of amphibian populations have raised questions about the relation of environmental change to the demise of certain amphibian species. Between 1974 and 1982, 11 populations of boreal toads ( Bufo boreas boreas ) in the West Elk Mountains of Colorado totally disappeared. The apparent cause of extinction of these toads was infection with the bacteria Aeromonas hydrophila . In this paper, the presence of disease in declining populations of these toads is used in conjunction with a variety of data from the literature to formulate a working hypothesis for explaining the cause of the decline of this species, and perhaps others:

     

Collapse of a Regional Frog Fauna in the Yosemite Area of the California Sierra Nevada, USA

There has been much concern about widespread declines among amphibians, but efforts to determine the extent and magnitude of these declines have been hampered by scarcity of comparative inventory data. We resurveyed a transect of the Sierra Nevada mountains in western North America that was carefully studied in the early 1900s. Our comparisons show that at least five of the seven frog and toad species in the area have suffered serious declines. One species has disappeared from the area entirely and a second species, formerly the most abundant amphibian in the area, has dwindled to a few small remnant populations. These declines have occurred in a relatively undisturbed, protected area and show some of the same patterns noted in other reports of amphibian declines. Introduced predatory fish, possibly interacting with drought-induced loss of refuge habitats, have contributed to the decline of some species. However, the overall cause of these dramatic losses remains unknown.     

Demographic Processes Underlying Population Growth and Decline in Salamandra salamandra

Abstract:  Human activity commonly has negative impacts on wildlife. Often, however, only a single element of the life cycle is affected, and it is unclear whether such effects translate into effects on population growth. This is particularly true for research into the causes of global amphibian declines, where experimental research focuses primarily on the aquatic larval stages but theory suggests these stages have only minor importance for population growth. We used data from long-term mark-recapture studies of two natural populations of the salamander Salamandra salamandra to confirm the predictions of population models. One population remained stable (i.e., stationary) throughout the 20 years of the study whereas the other declined to local extinction. We used mark-recapture models to break down population growth rate into its two main components, recruitment and adult survival. Survival of postmetamorphic salamanders was constant over time in the stable population, whereas the declining population was characterized by a decrease in survival and constant recruitment. Population growth was most sensitive to variation in adult survival. Current amphibian research focuses on preadult stages, and researchers assume recruitment is the most important determinant of population growth. This may not be the case. A better understanding of amphibian population dynamics is possible only through the integration of experiments, theory, and data from natural populations. Our results also suggest that amphibian conservation efforts should focus on all stages of the life cycle and their associated habitats.     

Possible Environmental Factors Underlying Amphibian Decline in Eastern Puerto Rico: Analysis of U.S. Government Data Archives

Abstract: The past three decades have seen major declines in populations of several species of amphibians at high elevations in eastern Puerto Rico, a region unique in the humid tropics because of the degree of environmental monitoring that has taken place through the efforts of U.S. government agencies. I examined changes in environmental conditions by examining time-series data sets that extend back at least into the 1980s, a period when frog populations were declining. The data include forest cover; annual mean, minimum, and maximum daily temperature; annual rainfall; rain and stream chemistry; and atmospheric-dust transport. I examined satellite imagery and air-chemistry samples from a single National Aeronautics and Space Administration aircraft flight across the Caribbean showing patches of pollutants, described as thin sheets or lenses, in the lower troposphere. The main source of these pollutants appeared to be fires from land clearing and deforestation, primarily in Africa. Some pollutant concentrations were high and, in the case of ozone, approached health limits set for urban air. Urban pollution impinging on Puerto Rico, dust generation from Africa ( potential soil pathogens), and tropical forest burning ( gaseous pollutants) have all increased during the last three decades, overlapping the timing of amphibian declines in eastern Puerto Rico. None of the data sets pointed directly to changes so extreme that they might be considered a direct lethal cause of amphibian declines in Puerto Rico. More experimental research is required to link any of these environmental factors to this problem.     

Assessing the global zoo response to the amphibian crisis through 20‐year trends in captive collections

Global amphibian declines are one of the biggest challenges currently facing the conservation community, and captive breeding is one way to address this crisis. Using information from the International Species Information System zoo network, we examined trends in global zoo amphibian holdings across species, zoo region, and species geographical region of origin from 1994 to 2014. These trends were compared before and after the 2004 Global Amphibian Assessment to assess whether any changes occurred and whether zoo amphibian conservation effort had increased. The numbers of globally threatened species (GTS) and their proportional representation in global zoo holdings increased and this rate of increase was significantly greater after 2004. North American, European, and Oceanian GTS were best represented in zoos globally, and proportions of Oceanian GTS held increased the most since 2004. South American and Asian GTS had the lowest proportional representation in zoos. At a regional zoo level, European zoos held the lowest proportions of GTS, and this proportion did not increase after 2004. Since 1994, the number of species held in viable populations has increased, and these species are distributed among more institutions. However, as of 2014, zoos held 6.2% of globally threatened amphibians, a much smaller figure than for other vertebrate groups and one that falls considerably short of the number of species for which ex situ management may be desirable. Although the increased effort zoos have put into amphibian conservation over the past 20 years is encouraging, more focus is needed on ex situ conservation priority species. This includes building expertise and capacity in countries that hold them and tracking existing conservation efforts if the evidence‐based approach to amphibian conservation planning at a global level is to be further developed.     

Interventions for Reducing Extinction Risk in Chytridiomycosis‐Threatened Amphibians

Wildlife diseases pose an increasing threat to biodiversity and are a major management challenge. A striking example of this threat is the emergence of chytridiomycosis. Despite diagnosis of chytridiomycosis as an important driver of global amphibian declines 15 years ago, researchers have yet to devise effective large‐scale management responses other than biosecurity measures to mitigate disease spread and the establishment of disease‐free captive assurance colonies prior to or during disease outbreaks. We examined the development of management actions that can be implemented after an epidemic in surviving populations. We developed a conceptual framework with clear interventions to guide experimental management and applied research so that further extinctions of amphibian species threatened by chytridiomycosis might be prevented. Within our framework, there are 2 management approaches: reducing Batrachochytrium dendrobatidis (the fungus that causes chytridiomycosis) in the environment or on amphibians and increasing the capacity of populations to persist despite increased mortality from disease. The latter approach emphasizes that mitigation does not necessarily need to focus on reducing disease‐associated mortality. We propose promising management actions that can be implemented and tested based on current knowledge and that include habitat manipulation, antifungal treatments, animal translocation, bioaugmentation, head starting, and selection for resistance. Case studies where these strategies are being implemented will demonstrate their potential to save critically endangered species. Intervenciones para Reducir el Riesgo de Extinción en Anfibios Amenazados por la Quitridiomicosis