鸟类惊飞距离及其影响因素

惊飞距离(FID)是指捕食者(包括人类)接近目标个体并导致其逃避时,捕食者与目标个体之间的距离。惊飞距离能很好地衡量动物个体在特定环境下的恐惧反应和风险权衡,是研究动物逃避行为的常用指标,并为物种保护提供科学依据。鸟类是研究逃避行为的理想对象,本文综述了影响鸟类惊飞距离的各种因素,可分为3类:栖息地因素(距隐蔽处的距离和生境开阔度等)、鸟类自身因素(生活史、体型和群体大小等)以及与捕食者相关的因素(捕食者的接近方向和速度等)。城市化也会影响鸟类的惊飞距离,导致城市中的鸟类通常比乡村生境的同种鸟类拥有更短的惊飞距离。习惯化、适应和生境选择是解释惊飞距离城乡差异的3种假说。研究鸟类的惊飞距离及其影响因素,有助于理解鸟类的逃避行为及其风险权衡机制,为物种保护中设立合理的缓冲区域及制定有效的保护管理措施提供科学依据。目前国内有关鸟类惊飞距离的研究多为行为观察和单一因素的影响,有待从不同因素的交互作用角度探讨鸟类的逃避行为并用于物种保护。     

食饵庇护所对斑块环境下Leslie-Gower捕食系统的影响

建立了一个显式含有空间庇护所的两斑块Leslie-Gower捕食者-食饵系统。假设只有食饵种群在斑块间以常数迁移率迁移,且在每个斑块上食饵间的迁移比局部捕食者-食饵相互作用发生的时间尺度要快。利用两个时间尺度,可以构建用来描述所有斑块总的食饵和捕食者密度的综合系统。数学分析表明,在一定条件下,存在唯一的正平衡点,并且此平衡点全局稳定。进一步,捕食者的数量随着食饵庇护所数量增加而降低;在一定条件下,食饵的数量随着食饵庇护所数量增加先增加后降低,在足够强的庇护所强度下,两物种出现灭绝。对比以往研究,利用显式含有和隐含空间庇护所的数学模型所得结论不一致,这意味着在研究庇护所对捕食系统种群动态影响时,空间结构可能起着重要作用。     

三峡水库香溪河库湾拟多甲藻昼夜垂直分布初步研究

具鞭毛的拟多甲藻（Peridiniopsis）是三峡水库多数支流库湾春季甲藻水华的优势种类。研究表明,昼夜垂直迁移是鞭毛藻重要的生态学特征。拟多甲藻形态学特征虽然也有鞭毛和自由游泳能力,但至今仍没有关于该种类昼夜垂直迁移的描述。定点昼夜垂直分层研究结果表明,三峡水库甲藻水华暴发的优势种之一拟多甲藻种3（Peridiniopsis sp．3）是绝对优势种,相对丰度达到45％;该物种与其它鞭毛藻相似,有昼夜垂直迁移的生态学特征,白天趋于在水体上层聚集分布,晚上趋于在水柱中随机分布;太阳光的昼夜交替是影响拟多甲藻昼夜垂直迁移的重要环境因素。     

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.     

基于水声学方法的天目湖鱼类季节和昼夜空间分布研究

采用水声学方法系统地对天目湖春夏秋冬四季鱼类水平和垂直空间分布进行了调查研究,同时对昼夜探测的差异性进行了比较,并对不同季节间鱼类聚群形态进行了探讨。研究结果表明,天目湖鱼类在不同季节间存在规律性水平迁移,从全湖角度分析,天目湖鱼类资源昼夜间的水平空间分布无明显差异特征,但在春末和夏季的局部区域里,昼夜间鱼类存在一定近岸—远岸的水平迁移;不同季节和昼夜间,鱼类垂直分布差异明显,且在存在温跃层的夏季7月昼间,鱼类密度垂直分布与水温的垂直分布关系密切,温跃层以下的鱼类密度基本为0;天目湖鱼类在四个季节都属于成群分布类型,但季节间鱼类聚群形态不同,在冬季的1月呈现出典型的聚集,相对于昼间,春夏季鱼类在夜间分布更为均匀、分散,且水平探测表明在夜间水体表层存在大量鱼类分布。     

大沙河水库拟柱孢藻昼夜垂直分布特征

为了解大沙河水库拟柱孢藻(Raphidiopsis raciborskii)昼夜垂直分布模式,于2018年9月20—21日(丰水期)和2018年12月31日(枯水期)对该水库拟柱孢藻进行昼夜定点分层采样,分析影响拟柱孢藻垂直分布的主要环境因子。用Morisita指数和平均滞留深度定量检验拟柱孢藻垂直分布格局;用方差分析检验拟柱孢藻是否存在昼夜垂直迁移现象,并采用多元回归方法分析拟柱孢藻垂直分布格局和环境因子的关系。结果表明:拟柱孢藻在丰水期呈现集群分布模式,主要分布于0.5～2 m水层,平均滞留深度为1.5 m;枯水期在6 m水深以上的水层呈现随机分布模式;丰水期和枯水期均无明显的昼夜垂直迁移现象;大沙河水库温跃层的出现是影响拟柱孢藻的昼夜垂直分布模式的主导因素。     

幼年竞争瓶颈对动力学行为的影响（英文）

通过建立具有非线性成熟率的食物网模型研究了幼年竞争瓶颈对种群动力学行为的影响,结论显示当竞争瓶颈比较弱的时,捕食者生活史中的幼年瓶颈对系统的影响要大于成年.模型存在两种可能的共存态或双稳定性,即消费者-捕食者和消费者平衡态共存,但是瓶颈不能诱导系统的双稳定性.进一步研究说明了选择不同的瓶颈或初始条件,瓶颈能够改变次级消费者对捕食者的净影响.     

千岛湖浮游甲壳动物垂直分布与昼夜垂直移动

2004年6月、9月、12月及2005年3月于千岛湖温馨岛站点(29°38′10.5″N,119°01′54.1″E)进行浮游甲壳动物垂直分布分层采样,分析千岛湖浮游甲壳动物的垂直分布特征及优势种昼夜垂直移动状况。结果显示,千岛湖浮游甲壳动物主要分布在10～21 m水层,不同季节中心水层分布深度12月9月6月3月;浮游动物昼夜垂直移动春(3月)、夏(6月)两季幅度较大,秋(9月)、冬(12月)季节幅度较小;浮游甲壳动物优势种在各个水层都有分布,密集区大都集中在中上水层(10～21 m),不同种类昼夜垂直移动幅度有所不同;昼夜垂直移动显著的种类有特异荡镖水蚤(Neutrodiaptanus incongruens)、近邻剑水蚤(Cyclops vicinus)、球状许水蚤(Schmackeria forbesi)、透明溞(Daphnia hyaline)、长额象鼻溞(Bosmina longirostris),不显著的种类为右突新镖水蚤(Neodiaptomus schmackeri)、短尾秀体溞(Diaphanosoma brachyurum)。光照、温度、饵料是影响千岛湖浮游甲壳动物垂直分布及昼夜垂直移动的主要因素。     

鼎湖山针阔混交林锥栗种子距离制约研究

Janzen-Connell 距离制约假说认为:扩散到远离母树地点的种子,更容易逃避种子捕食者和病原体侵染。验证锥栗(Castanopsis chinensis)种子是否支持该假说,可以预测锥栗种群分布格局,解释锥栗种群更新不良的原因。在鼎湖山针阔混交林内,选择离成年母树3、10和15 m处,进行种子放置实验,以及种子消毒和未消毒埋土实验。在无覆盖实验中,10 m处大种子的消失数始终最大,种子离母树距离和种子大小两个因素对种子消失数均没有显著性影响。在排除哺乳动物实验中,种子放置第一周,种子消失数均很少。整个试验期,种子离母树距离和种子大小两个因素对种子消失数也没有显著性影响。在病原体实验中,埋土前两个月,经过消毒的种子袋中种子均保存完好,没有病原体侵染。埋土的种子从第三个月到第六个月,不同距离处的种子,以及消毒和未消毒处理的种子,被侵染数之间均有显著性差异;被侵染的种子数到第六个月趋于稳定。因此,锥栗种子被脊椎动物取食,不呈现距离制约(Distance-dependent)格局;而被病原体侵染的种子命运则支持距离制约假说。     

北京十渡水库浮游植物群落昼夜垂直分布特征

浮游植物的昼夜变化节律及垂直分布是影响水生生态系统初级生产力的重要因素,受浮游植物自生生理特点及环境影响因素的双重影响。为了解淡水生态系统浮游植物的昼夜垂直分布特征及环境影响因素,2015年4月下旬,选择北京十渡水库深水区和浅水区两个采样点,对其浮游植物群落和相关环境因子进行了一天中10:00、14:00、19:30和5:00四个时间点分层采样,并进行水样的理化检测和浮游植物样品的鉴定。结果表明:十渡水库的浮游植物垂直分布格局在深水区和浅水区有较大差异;总体上,浮游植物密度均为白天较高,且大多数种类白天有向上层集中的趋势;深水区,大多数环境因子分层格局较显著,浮游植物的垂直分布主要受温度、光照、溶解氧、氮、磷营养盐含量等因素影响,优势属微囊藻属符合蓝藻群体夜间向水表迁移的特点,可能受到光照的影响;多甲藻属大多分布于深水区水体底层,其垂直变化受控于温度、光照等因素,舟形藻属大多分布于深水区水体表层;浅水区,浮游植物垂直分布波动较大,大多数环境因子的分层不明显,脆杆藻属与TDS呈正相关,栅藻属主要受到溶解氧和水温的影响。     

Control mechanisms of diel vertical migration: theoretical assumptions

We explore control mechanisms underlying the vertical migration of zooplankton in the water column under the predator-avoidance hypothesis. Two groups of assumptions in which the organisms are assumed to migrate vertically in order to minimize realized or effective predation pressure (type-I) and to minimize changes in realized or effective predation pressure (type-II), respectively, are investigated. Realized predation pressure is defined as the product of light intensity and relative predation abundance and the part of realized predation pressure that really affects organisms is termed as effective predation pressure. Although both types of assumptions can lead to the migration of zooplankton to avoid the mortality from predators, only the mechanisms based on type-II assumptions permit zooplankton to undergo a normal diel vertical migration (morning descent and evening ascent). The assumption of minimizing changes in realized predation pressure is based on consideration of DVM induction only by light intensity and predators. The assumption of minimizing changes in effective predation pressure takes into account, apart from light and predators also the effects of food and temperature. The latter assumption results in the same expression of migration velocity as the former one when both food and temperature are constant over water depth. A significant characteristic of the two type-II assumptions is that the relative change in light intensity plays a primary role in determining the migration velocity. The photoresponse is modified by other environmental variables: predation pressure, food and temperature. Both light and predation pressure are necessary for organisms to undertake DVM. We analyse the effect of each single variable. The modification of the phototaxis of migratory organisms depends on the vertical distribution of these variables.     

Two hundred years of zooplankton vertical migration research

Vertical migration is a geographically and taxonomically widespread behaviour among zooplankton that spans across diel and seasonal timescales. The shorter-term diel vertical migration (DVM) has a periodicity of up to 1 day and was first described by the French naturalist Georges Cuvier in 1817. In 1888, the German marine biologist Carl Chun described the longer-term seasonal vertical migration (SVM), which has a periodicity of ca. 1 year. The proximate control and adaptive significance of DVM have been extensively studied and are well understood. DVM is generally a behaviour controlled by ambient irradiance, which allows herbivorous zooplankton to feed in food-rich shallower waters during the night when light-dependent (visual) predation risk is minimal and take refuge in deeper, darker waters during daytime. However, DVMs of herbivorous zooplankton are followed by their predators, producing complex predator–prey patterns that may be traced across multiple trophic levels. In contrast to DVM, SVM research is relatively young and its causes and consequences are less well understood. During periods of seasonal environmental deterioration, SVM allows zooplankton to evacuate shallower waters seasonally and take refuge in deeper waters often in a state of dormancy. Both DVM and SVM play a significant role in the vertical transport of organic carbon to deeper waters (biological carbon sequestration), and hence in the buffering of global climate change. Although many animal migrations are expected to change under future climate scenarios, little is known about the potential implications of global climate change on zooplankton vertical migrations and its impact on the biological carbon sequestration process. Further, the combined influence of DVM and SVM in determining zooplankton fitness and maintenance of their horizontal (geographic) distributions is not well understood. The contrasting spatial (deep versus shallow) and temporal (diel versus seasonal) scales over which these two migrations occur lead to challenges in studying them at higher spatial, temporal and biological resolution and coverage. Extending the largely population-based vertical migration knowledge base to individual-based studies will be an important way forward. While tracking individual zooplankton in their natural habitats remains a major challenge, conducting trophic-scale, high-resolution, year-round studies that utilise emerging field sampling and observation techniques, molecular genetic tools and computational hardware and software will be the best solution to improve our understanding of zooplankton vertical migrations.     

Plasticity of Daphnia magna life history traits in response to temperature and information about a predator

1. Exudates from predators often elicit early maturation in Daphnia, which may protect them from predation. Diel vertical migration (DVM) is also a predator-avoidance device and affects life history traits because of the variable temperature experienced during migration. This study asks, therefore, how do these two effects interact and what are the net costs and benefits of the two defences combined? 2. Key life history features were studied in a two factorial life table experiment in a monoclonal cohort of Daphnia magna to quantify the costs of predator-induced defences. 3. The costs of DVM, associated with low temperature, yielded a 30% decrease in the intrinsic rate of population increase. This was caused by later maturation and longer egg development time, despite a higher fecundity. 4. Chemical information that predators were present resulted in smaller, more numerous offspring, but had no significant effect on size and age at first reproduction. The costs of induction were therefore associated with smaller, and thus presumably lower quality, offspring. 5. Changes in life history induced by fish exudates were independent of the shifts caused by low temperature. 6. The measure of fitness chosen to assess the costs of induced defences is important because the costs often depend on the environment.     

Diel vertical migration of zooplankton following optimal food intake under predation

A model is developed to investigate the trade-offs between benefitsand costs involved in zooplanktonic diel vertical migration(DVM) strategies. The ‘venturous revenue’ (VR) isused as the criterion for optimal trade-offs. It is a functionof environmental factors and the age of zooplankter. Duringvertical migration, animals are assumed to check instantaneouslythe variations of environmental parameters and thereby selectthe optimal behavioral strategy to maximize the value of VR,i.e. taking up as much food as possible with a certain riskof mortality. The model is run on a diel time scale (24 h) infour possible scenarios during the animal’s life history.The results show that zooplankton can perform normal DVM balancingoptimal food intake against predation risk, with the profileof DVM largely modified by the age of zooplankter.     

Diel vertical migration of copepods and its environmental drivers in subtropical Bahamian blue holes

Aquatic Ecology - Diel vertical migration (DVM) is the most common behavioral phenomenon in zooplankton, and numerous studies have evaluated DVM under strong seasonality at higher latitudes. Yet,...     

Small-scale diel vertical migration of zooplankton in the High Arctic

Diel vertical migration (DVM) of zooplankton is considered less prominent at high latitudes where diel changes in irradiance are minimal during periods of midnight sun and polar night, leaving zooplankton without a temporal refuge and thus eliminating a key advantage of DVM. One of the shortcomings of previous DVM studies of zooplankton based on net sampling is that the depth resolution often has been too coarse to detect vertical migrations over short distances. We investigated DVM of zooplankton during August 2010 in drifting sea ice northeast of Svalbard (~81.5°N, ~30.5°E). Classical DVM behaviour (midnight rising, midday sinking) was observed between 20 and 80 m in young copepodite stages (CI–III) of Calanus finmarchicus and Calanus glacialis. The copepods Microcalanus spp., Pseudocalanus spp., Oithona atlantica, Oithona similis and Triconia borealis, alongside Eukrohnia hamata, Limacina helicina, and Fritillaria spp., all displayed signs of DVM. We conclude that zooplankton exhibit DVM in ice-covered waters over rather short distances to optimise food intake in the presence of predators.     

Diel vertical migration of Arctic zooplankton during the polar night

High-latitude environments show extreme seasonal variation in physical and biological variables. The classic paradigm of Arctic marine ecosystems holds that most biological processes slow down or cease during the polar night. One key process that is generally assumed to cease during winter is diel vertical migration (DVM) of zooplankton. DVM constitutes the largest synchronized movement of biomass on the planet, and is of paramount importance for marine ecosystem function and carbon cycling. Here we present acoustic data that demonstrate a synchronized DVM behaviour of zooplankton that continues throughout the Arctic winter, in both open and ice-covered waters. We argue that even during the polar night, DVM is regulated by diel variations in solar and lunar illumination, which are at intensities far below the threshold of human perception. We also demonstrate that winter DVM is stronger in open waters compared with ice-covered waters. This suggests that the biologically mediated vertical flux of carbon will increase if there is a continued retreat of the Arctic winter sea ice cover.     

Modeling patterns of zooplankton diel vertical migration

Realized predation pressure, defined as the product of predationpressure and light intensity, expresses the mortality pressuredue to visual predation. The part of realized predation pressurewhich is sensed by organisms is here considered to be relatedto food level and temperature. This partly realized predationpressure is referred to as sensed predation pressure. We proposea possible control mechanism of diel vertical migration (DVM):organisms move vertically following the minimum change in sensedpredation pressure. To investigate this assumption, we presenta math ematical model of DVM. We assume that when predatorsare present, the food level is above a minimal level, and temperatureis higher than the tolerance of organisms to growth, prey organismsundertake DVM following the minimum change in sensed predationpressure. We examine how patterns of migration may be affectedby changes in water clarity, predation pressure, food leveland temperature. This work supports the assumption that minimizingchanges in sensed predation pressure can explain the wide variationin the vertical profile of zooplankton.     

Diel vertical migration by males,females, copepodids and nauplii in a limnetic population of diaptomus (Copepoda)

Diel vertical migration (DVM) by the sexes and life history stages of the copepod Diaptomus novamexicanus (Herrick) was investigated during two summers in a subalpine lake (Castle Lake, California, USA). Migratory behavior was quantified repeatedly by 1300 and 21–2200 hr sampling in the epilimnion. Population density and vertical distribution were estimated routinely at 1300 hr and at 2200 hr on selected dates. Males had greater night to day biomass differentials and ratios than females. The sexes showed comparable DVM participation (% of total biomass migrating) and amplitudes of migration (distance of ascent). Copepodids displayed higher participation, night/day ratios and amplitudes than younger copepods, but adult participation differed only from that of nauplii. Active participation in high amplitude ascents thus increased with age and was greatest in adult males. Analysis suggests that such relative behaviors probably occur in most limnetic Diaptomus, and that the magnitude of ascent into the epilimnion is associated with daytime vertical distribution.     

A free-drifting mimic of vertically migrating zooplankton

Many zooplankton species perform diel vertical migrations (DVM) which, in conjunction with vertical current shear, complicate the use of conventional fixed-depth drifters to account for advection. Here we illustrate the first use of an autonomous Vertically Migrating Drifter (VMD) to mimic DVM behavior. The vehicle resides within different subsurface layers at different times of day through either active hover cycles or passive drifts. It moves vertically between these layers at speeds comparable to those recorded for migratory populations. In this mode, it can be utilized as a tool to estimate the advection of migratory zooplankton in regions of high vertical current shear and can be employed as a Lagrangian tracer when attempting to sample the same population repeatedly over time.