1、Q1 群落、结构和稳定性 要 点群 落群落（community）是在相同时间聚集在同一地段上的许多物种种群（species populations）的集合。它的特性是由个体之间的相互作用如竞争（competition）和寄生（parasitism）决定的。群落也能够从更广阔的角度和物种多样性（species diversity）、食物网（food-webs）、能量流（energy flow）和同资源种团（guilds）中种间的相互作用来观察它的特性。The community is an assemblage of species populations that occur together
2、 in the same place at the same place at the same time.It has properties determined by the imteractions among individuals such as competition and parasitism.The community can also be viewed from the broader perspective in terms of species diversity,food-webs,energy flow and the interactions among gui
3、lds of species.Key NotesThe community群落结构一个群落的物种多样性取决于群落含有的不同种的数量即种丰富度（the species richness）和种多度的均匀性（the evenness of species abundance）。多样性指数（diversity indices）可以通过这两个因子计算出来。表达种丰富和种均匀度综合的另一种方式是通过种的相对多度对种的顺序作图。多样性能够在局域群落（local community）、地区（region）和最广阔的地理尺度（geographic scale）（如大陆）三个不同的空间尺度上测算它。这样就产生了a
4、、和多样性。The species diversity of a community depends on the number of different species it contains(the species richness)and the evenness of species abundance across species.Diversity indices can be calculated to take into account both of these factors.Another way of representing species richness and
5、evenness together is to plot the relative abundance of species against rank order of species abundance.Diversity can be measured over the three different spatial scales of the local community,the region and the broadest geographic scale(e.g.the continent).This yields alpha()-,beta()-and gamma()-dive
6、rsity.Community structure群落边界群落不会突然中断，而是逐渐的过渡到其他群落，因为各个物种是逐渐受到它们的环境耐受力限制的。这一点可以通过梯度分析来得到证明，梯率分析重点在于物种分布重叠区域。分类和排序的统计方法允许群落的边界在这个连续体上重叠。分类技术分出了生态学上不同的物种或地段，获得了客观等级。排序并不是企图勾画出边界，而是根据它们在分布上的相似性而勾画出物种集团或地段。Communities do not end abruptly but grade into one another as individual species encounter the lim
7、its of their environmental tolerance.This can be demonstrated through gradient analysis,which focuses on the overlapping distributions of individual species.The statistical methods of classification and ordination allow community boundaries to be superimposed on this continuum.Classification techniq
8、ues separate ecologically different species or sites yielding objective classes.Ordination does not attempt to draw boundaries but groups species or sites according to how similar they are in their distributions.Community boundaries同资源种团同资源种团是许多占据相似生态位的物种组合的集团；如以阔叶树为食物的许多昆虫就形成一个同资源种团。一些研究已经表明，在一个群落内
9、的某些同资源种团中的总物种的比例是不变的。这就表明也许有某一共同的“规则”在统治着群落结构。Guilds are groups of species that occupy similar niches;for example,insects feeding on broad-leaved trees form one guild.Some studies have found constancy in the proportion of total species in certain guilds within a community.This indicates that there m
10、ay be certain common rules governing community structure.Guilds群落的复杂性、多样性和稳定性稳定性有两个组成成分恢复力（resilience）和抵抗力（resistance）。这两个指标描述了群落在受到干扰后的恢复能力和抵御变化的能力。复杂性被认为是决定群落恢复力和抵抗力的重要因素。然而群落越复杂并不意味着群落越稳定。复杂性增加已经显示会导致不稳定。此外，群落的不同组分（如种丰富度和生物量）也许对干扰有不同反应。具有较低生产力的群落（如冻原）其恢复力是最低的。相反，较弱的竞争可以使许多的物种共存，从而减少群落的不稳定性。茫茫的北极冻
11、原There are tow components to stability resilience and resistance,which describe the communitys ability to recover from disturbance and to resist change.Complexity is thought to be important in determining resilience and resistance,However,more complex communities are not necessarily the most stable;
12、increased complexity has been shown to lead to instability.In addition,different components of the communities(e.g.species richness and biomass)may respond differently to disturbance.Communities with a low productivity(e.g.tundra)to be the least resilient.In contrast,weak competition permits coexist
13、ence among species and reduces community instability.Community complexity,diversity and stability相关主题资源分配（见I3）食物链（见P3）营养复杂性与稳定性食物链的长度也许能够影响群落的恢复力。具有不同营养连接水平的许多群落模型，显示复杂性导致恢复力和稳定性下降。然而，这样的研究应该被谨慎地解释，因为真正的群落所具有的特性在零群落模型中并没有被发现。稳定性也依赖于环境状况一个脆弱的（复杂的或多样的）群落也许能够在一个稳定和可预知的环境中持续下去，而在一个多变的和不可预知的环境中，仅仅简单的和生长旺
14、盛的群落才能够生存下去。Related topicsResource partitioning (I3)Food chains (P3)Trophic complexity and stabilityFood chain length may influence the resilience of the community.Models of communities with different levels of trophic connectance show that complexity reduces resilience and stability.However,such st
15、udies should be interpreted with caution,as real communities msy possess important attributes mot found in the communities of null models.Stability also depends on environmental conditions a fragile(complex or diverse)community may persist in a stable and predictable environment,while in a variable
16、and unpredictable environment only simple and robust communities will survive.Q2 岛屿群落与移殖 要 点物种-面积关系岛屿上（或一个地区中）物种数目会随着岛屿面积的增加而增加，最初增加十分迅速，当物种接近该生境所能承受的最大数量时，增加将逐渐停止。物种数目的对数与面积对数的坐标图显示的是一个线性关系。对于海洋岛屿和生境岛屿来说，这些双对数坐标图直线的斜率，大多在0.240.34之间。对于连续生境内的亚区域，斜率接近0.1。随着面积增加，物种多样性增加的效果在岛屿上要比连续生境内明显。岛屿The number of
17、species on an island(or in any area)will increase with the size of the island.The increase is initially rapid,tailing off at the maximum number of species for a given habitat.A plot of log species number against log area gives a linear relationship.For oceanic islands or islands of habitat,the slope
18、s of these log-log plots mostly fall within the range 0.24-0.34.For subareas within continuous habitat,the slope is around 0.1.The effect of increasing species diversity with increasing area is more pronounced on islands than within continuous habitat.Key NotesThe species-area relationship岛屿生物地理学麦克阿
19、瑟和威尔逊的岛屿生物地理学理论指出，岛屿上物种的数目是由新移殖来的物种和以前存在物种的灭绝之间的动态平衡决定的。当移殖种的数目增加时，到达岛屿的移殖来的物种的数目会随着时间的推移而减少。相反，当物种之间的竞争变得强烈时，灭绝的速率就会增加。当灭绝和移殖的速率达到相等时，物种的数目就处于平衡稳定状态。模型研究也证明了物种的数目会随着岛屿面积的增加而增加，和随着距移殖者源距离的缩短而增加。对模型研究有利的证据，是由对除去动物的岛屿上物种的再移殖的观察，和对最近隔离的岛屿物种的丧失结果所提供的。当与邻近大陆对照的时候，灭绝和移殖过程说明了岛屿植物区系和动物区系的衰亡。MacArthur and Wi
20、lsons theory of island biogeography states that the number of species found on an island is determined by a dynamic equilibrium between the immigration of new colonizing species and the extinction of previously established ones.As the number of colonizing species increases,the number of immigrants a
21、rriving on the island decreases over time.In contrast,as competition among species becomes more intense,the extinction rate increases.The point at which extinction and colonization rates are equal gives the number of species at equilibrium.the model also accounts for the increase in species number w
22、ith increasing island size and decreasing distance from a source of colonists.Extinction and colonization account for the depauperate flora and fauna of islands when compared to the adjacent mainland.Island biogeography岛屿和异质种群异质种群理论已经替代了岛屿生物地理学来解释片断化生境的“岛屿”种群行为。异质种群含有许多种群，这些种群之间通过迁入和迁出而交换个体。与岛屿不同，生境
23、斑块（patch）是在景观镶嵌板块（landscape mosaic）之中的，景观板块能够影响斑块的性质和它所含的物种种类。相关主题种内竞争（见I2）保育对策（见V2）稀有物种、生境损失和灭绝（见V1）Related topicsIntraspecific competition(I2)Conservation strategies (V2)Rare species,habitat loss and extinction (V1)Islands and metapopulationsMetapopulation theory has superseded island biogeography
24、 in explaining the behavior of populations in islands of fragmented habitat.A metapopulation consists of a number of populations that exchange individuals through immigration and emigration.Unlike islands,habitat patches are embedded in a landscape mosaic that can influence the quality of the patch
25、and the species it will contain.Q3 群落格局、竞争和捕食 要 点群落集合集合规则（assembly rule）的概念企图解释自然群落是如何不同于来自物种库中的物种而随机装配出来的群落。群落集合也许能被生境类型、物种移殖和定居，或者种内的相互关系，像捕食、寄生和竞争所影响。集合规则研究群落组成中的格局，将那些由“零(null)”群落模型所产生的格局与真实的群落格局相比较。The concept of assembly rules attempts to explain how natural communities vary from random assemb
26、lages derived from the range of available species(the species pool).Community assembly may be influenced by habitat type,species colonization and establishment,and/or by interspecific relationships such as predation,parasitism and competition,Assembly rule studies investigate patterns in community m
27、ake-up,comparing real community patterns with those generated by null community models.Key NotesCommunity assembly竞 争竞争可能是形成群落结构的一个重要力量，但是在调查的时候，它又不一定是重要的。过去竞争的痕迹在群落中可以留下很深的烙印（像生态位的分化）。竞争的一些研究已经表明，生态学上相似物种组成的同资源种团当中，仅仅只有一个成员在群落中能够生存，这就意味着其他相似物种被竞争排斥了。岛屿上超飘流的鸟类物种的分布也支持了该理论，即竞争导致了群落的结构化。新西兰岛屿Competiti
28、on can be an important force shaping community structure but is not necessarily significant at the time of investigation.The ghost of competition past can leave a strong imprint on a community(e.g.as niche differentiation).Some studies of competition have shown that only one member of a guild of eco
29、logically similar species tends to be present in the community,suggestive of competitive exclusion of other similar species.The distribution of supertramp bird species on islands also supports the theory that communities are structured by competition.Competition食肉动物选择捕食和转换猎物能够使稀有物种免遭捕杀。这种行为能够导致许多相对稀
30、少的物种在同一个群落中共存。食草动物食草动物对植物群落有两个作用：（i）它们选择摄食影响群落的物种多度。（ii）啃食抑制了竞争物种的生长，因此加速和维持了低竞争物种的多样性。当啃食强度很强时，物种多样性降低，物种会局部灭绝。Grazing animals have two effects on plant communities:(i)their selective feeding affects species abundance in the community,and(ii)grazing suppresses the growth of competitive species thus
31、 enhancing and maintaining the diversity of less competitive species.When grazing intensity is very high,diversity can be reduced as species are forced to local extinction.GrazersSelective predation and prey switching can leave rarer species unpredated.This behavior can lead to the coexistence of a
32、large number of relatively rare species in the same community.Carnivores相关主题种内竞争（见I2）演替（见R1）资源分配（见I3）群落对干扰的反映（见R2）关键物种关键（keystone）物种在群落中有一个重要的和不成比例的作用。关键种可能是顶端的捕食者，像北方的海獭；然而这个词可以运用在任何一个物种上，只要这个物种被移去时会对群落结构造成重大影响。人工繁殖的小海獭塔贝儿 Related topicsIntraspecific competition(I2)Community responses toResource pa
33、rtitioning (I3)disturbance (R2)Succession (R1)Keystone speciesA keystone species has a significant and disproprtionate effect on the community.Keystone species can be top predators such as the northern sea otter;however,the term can be usefully applied to any species whose removal would have a significant effect on community structure.
