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2.1.4 lepidoptera★
A small number of the forest species of Lepidoptera (moths and butterflies, which exist as caterpillars during most of their life cycle) exhibit显示, 显出 regularly recurring pattern图形[谱, 表]of population growth and decline—such fluctuations in population are known as population cycles.
自然现象:毛毛虫都有自己的生命周期曲线,数量增减
Although many different variables influence population levels, a regular pattern such as a population cycle seems to imply a dominant, driving force. Identification of that driving force, however, has proved surprisingly elusive despite considerable research.
科学家想要找一个决定因素,但却很难
The common approach of studying causes of population cycles by measuring the mortality caused by different agents, such as predatory birds or parasites, has been unproductive in the case of Lepidoptera. Moreover, population ecologists’ attempts to alter cycles by changing the caterpillars’ habitat and by reducing caterpillar populations have not succeeded.
一般的变量因素都试过了:捕食鸟,寄生虫,栖息地都不是决定因素
In short, the evidence implies that these insect populations, if not self-regulating自动调节, may at least be regulated by an agent动因 more intimately密切地 connected with the insect than are predatory birds or parasites.
如果不是毛毛虫自我调节,就应该有他因了
Recent work suggests that this agent maybe a virus.
这个因素可能为病毒
For many years, viral disease had been reported in declining populations of caterpillars, but population ecologists had usually considered viral disease to have contributed to the decline once it was underway在进行中的 rather than to have initiated it.
传统观念虽然看到病毒这个因素,但只把它作为过程中变量,而不是起始时的变量
The recent work has been made possible by new techniques of molecular biology that allow viral DNA to be detected at low concentrations in the environment.
分子生物学的技术改进,此病毒的DNA在低浓度条件下也能被观察
(细节内容:生命循环机理) Nuclear polyhedrons viruses are hypothesized to be the driving force behind population cycles in Lepidoptera in part在某种程度上, 部分地 because the viruses themselves follow an infectious cycle in which, if protected from direct sun light, they may remain virulent for many years in the environment, embedded in durable crystals of polyhedron protein. Once ingested by a caterpillar, the crystals dissolve, releasing the virus to infect the insect’s cells. Late in the course of在…期间, 在…过程中the infection, millions of new virus particles are formed and enclosed in polyhedron crystals. These crystals reenter the environment after the insect dies and decomposes, thus becoming available to infect other caterpillars.
此病毒的生命循环和毛毛虫的生命循环是配合的(他有点像初中学的猪肉绦虫,在自然环境和寄主之间循环)
One of the attractions of this hypothesis is its broad applicability.
先小让步:此理论的广泛适用性还有待商榷
Remarkably, despite significant differences in habitat and behavior, many species of Lepidoptera have population cycles of similar length, between eight and eleven years. Nuclear polyhedrosis viral infection is one factor these disparate species share.
作者观点还是个人委婉支持的,病毒因素可能还是很重要的 |
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