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　　Competition

　　When several individuals of the same species or of several different species

depend on the same limited resource,a situation may arise that is referred to as

existence of competition has been long known to naturalists;its

effects were described by Darwin in considerable ition among

individuals of the same species(intraspecies competition),one of the major

mechanisms of natural selection,is the concern of evolutionary ition

among the individuals of different species(interspecies competition)is a major

concern of is one of the factors controlling the size of competing

populations,and extreme cases it may lead to the extinction of one of the competing

was described by Darwin for indigenous New Zealand species of animals

and plants,which died out when competing species from Europe were introduced.

　　当同一物种的不同个体或不同的物种都依靠同一有限资源时，这种情况往往会引发成所

谓的竞争。竞争的存在已为生物学家们所熟知，其结果也已被达尔文详尽叙述过。同一物种

不同个体之间的竞争(种内竞争)，作为自然选择的一个主要原理，现在属于进化生物学。不

同物种个体之间的竞争(种间竞争)是生态学的主要部分。它是控制有竞争关系的种群数量的

一个因素，而其极端情况可能导致竞争的一方灭绝。达尔文在描述新西兰本土动植物物种在

与引进的欧洲物种的竞争中灭绝时讲到该情况。

　　No serious competition exists when the major needed resource is in superabundant

supply,as in most cases of the coexistence of herbivores(plant

eaters).Furthermore,most species do not depend entirely on a single resource,if the

major resource for a species becomes scarce,the species can usually shift to

alternative more than one species is competing for a scarce resource,the

competing species usually switch to different alternative ition is

usually most severe among close relatives with similar demands on the

it may also occur among totally unrelated forms that compete for the same

resource,such as seed-eating rodents and effects of such competition are

graphically demonstrated when all the animals or all the plants in an ecosystem come

into competition,as happened 2 million years ago at the end of Pliocene,when North

and South America became joined by the Isthmus of and South American

species migrating across the Isthmus now came into competition with each

result was the extermination of a large fraction of the South American mammals,which

were apparently unable to withstand the competition from invading North American

species—although added predation was also an important factor.

　　当主要需求的资源能充分供给时，竞争就不会很激烈，正如很多情况下植食动物都能够

共存。而且绝大部分物种并不只依靠一种资源，当某物种的主要资源匮乏时，它们常转向其

它候选资源。如果多个物种竞争同一稀缺资源，他们常会转向不同的候选资源。近亲之间的

竞争往往最激烈，因为他们对环境有相似需求。但激烈竞争也可能发生在毫不相关却需要同

一资源的物种之间，例如吃种子的啮齿动物和蚂蚁。当一个生态系统中的所有动植物都参与

到竞争中来时竞争的影响将表现得淋漓尽致，比如在两百万年前上新世末期当南、北美洲在

巴拿马地峡处聚拢时所发生的一切。南、北美洲的物种可以穿越地峡而相互竞争。结果是大

量南美洲哺乳动物因抵抗不了来自北美洲物种的竞争而灭绝----尽管过度捕杀也是一个很重

要的因素。

　　To what extent competition determines the composition of a community and the

density of particular species has been the source of considerable

problem is that competition ordinarily cannot be observed directly but must be

inferred from the spread or increase of one species and the concurrent reduction or

disappearance of another Russian biologist performed numerous

two-species experiments in the laboratory,in which one of the species became extinct

when only a single kind of resource was the basis of these experiments

and of field observations,the so-called law of competitive exclusion was

formulated,according to which no two species can occupy the same us

seeming exceptions to this law have since been found,but they can usually be explained

as cases in which the two species,even though competing for a major joint resource,did

not really occupy exactly the same niche.

　　竞争在多大程度上决定群落的组成和某特定物种的密度一直备受争议。问题是竞争通常

无法直接观察得到而必须通过某一物种的扩张或增加而另外一种物种同时减少或消失的对比

中推测出来。俄罗斯生物学家进行了大量的两物种的室内实验，结果表明当只提

供一种资源时其中一个物种将会灭绝。基于以上实验和实地观察，所谓的竞争灭绝法则是成

立的，因为两个物种不可能同时完全占有同一有限资源。不过也发现了很多例外，但这些情

况下两个物种，尽管会争夺某一主要资源，但它们争夺的资源不完全相同。

　　Competition among species is of considerable evolutionary

physical structure of species competing for resources in the same ecological niche

tends to gradually evolve in ways that allow them to occupy different ing

species also tend to change their ranges so that their territories no longer

evolutionary effect of competition on species has been referred to as

“species selection”;however,this description is potentially the

individuals of a species are subject to the pressures of natural effect

on the well-being and existence of a species is just the result of the effects of

selection on all the individuals of the species selection is actually

a result of individual selection.

　　物种间的竞争对进化至关重要。争夺同一生态资源的物种趋向于朝着依赖不同资源的方

向进化。相互竞争的物种会逐渐改变他们的活动范围使其领地不再重叠。竞争对进化的影响

称为“物种选择”，但这一描述有很大误导性。只有某一物种中的个体才能面临自然选择的压

力。某一物种的繁盛或生存正是其所有个体自然选择的结果。因此物种选择实际上是个体选

择的结果。