Effects of plant density on the survival rate of cabbage pests
Effects of plant density on the survival rate of cabbage pests
复制标题
种植密度对甘蓝害虫成活率的影响
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
E. Yano
中科院分区：
文献类型：
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作者：
K. Yamamura;E. Yano
食草动物的种群密度不仅取决于时间尺度，也取决于空间尺度。在一个小规模的短期实验中，从周围区域进入的个体数量将是决定食草动物密度的最有影响力的因素。然而，在大规模的长期实验中，食草动物的密度将受到田间个体存活率的影响，因为大多数食草动物种群来自田间发育的亲本。因此，要想预测大规模的食草动物长期密度，重点应放在存活率的估计上。为了阐明植物密度对甘蓝害虫大规模长期大量发生的影响，我们研究了三种鳞翅目害虫的存活率，小白色蝴蝶Pieris raiscrucivora Boisduval甜菜夜蛾Autographa nigrisigna（步行者）（夜蛾科）和小菜蛾Plutella xylostella（Linnaeus）（Yponomeutidae）在两种株距水平下（稀疏样地，2 m × 2 m间距;密集样地，0.5 m × 0.5 m间距）的种群数量变化。四个街区的实验在两个季节重复。每株植物的卵数是在稀疏的情节比在密集的情节为所有物种。相反，卵和幼虫的存活率在稀疏样地中低于在密集样地中。卵在稀疏样地的存活率较低主要是由密度依赖性造成的，而幼虫在稀疏样地的存活率较低主要是由密度的直接影响造成的。因此，从长远来看，在稀疏种植的农田中，由于幼虫的死亡率较高，食草动物的密度可能会降低。
The population density of herbivores depends on the spatial scale as well as the temporal scale. In a small-scale, short-term experiment, the number of individuals entering from the surrounding area will be most influential in determining the herbivore density. In large-scale, long-term experiments, however, the density of herbivores will rather be influenced by the survival rate of individuals inside the field because most of the herbivorous population derives from the parents that developed inside the field. If we want to predict the large-scale long-term density of herbivores, therefore, emphasis should be placed on the estimation of survival rate. To elucidate the effects of plant density on the large-scale long-term abundance of cabbage pests, we examined the survival rates of three lepidopterous pests, the small white butterfly Pieris rapae crucivora Boisduval (Pieridae), the beet semi-looper Autographa nigrisigna (Walker) (Noctuidae), and the diamondback moth Plutella xylostella (Linnaeus) (Yponomeutidae) under two levels of plant spacing (sparse plot, 2 m × 2 m interval; dense plot, 0.5 m × 0.5 m interval). The experiment with four blocks was repeated in two seasons. The number of eggs per plant was larger in the sparse plots than in the dense plots for all species. The survival rate of eggs and larvae, on the contrary, was lower in the sparse plots than in the dense plots. The lower survival rate of eggs in the sparse plots was mainly caused by the density dependency, while the lower survival rate of larvae in the sparse plots was mainly caused by the direct effects of plant density. It was thus suggested that the density of herbivores may become lower in the sparsely planted field in the long run because of the higher mortality of larvae.