HERBIVORES AND THE NUMBER OF TREE SPECIES IN TROPICAL FORESTS
HERBIVORES AND THE NUMBER OF TREE SPECIES IN TROPICAL FORESTS
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DOI：
10.1086/282687
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发表时间：
1970-01-01
影响因子：
2.9
通讯作者：
JANZEN, DH
中科院分区：
文献类型：
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作者：
JANZEN, DH
许多低地热带森林生境的特点是树种数量多，每一种成虫密度低，同种成虫之间距离长。我认为，这三种特征在很大程度上是捕食者对种子和幼苗采取行动的结果。提出了一个模型，可以详细检查不同捕食者、分散剂、种子作物大小等对这三个性状的影响。简而言之，任何提高捕食者捕食某一树种种子和幼苗效率的事件，都可能导致该树种成虫种群密度的降低和/或增加新成虫与其父母之间的距离。这两种情况都会给其他树种的栖息地带来更多的空间，因此，如果在进化过程中种子来源是可用的，树种的总数就会增加。当一个人从潮湿的热带低地迁移到干燥的热带或温带地区时，假设栖息地中的种子和幼苗捕食者在防止一种或几种树种通过竞争优势垄断栖息地方面的效率越来越低。这种捕食者效率的降低是由于自然环境的严重性和不可预测性的增加，这反过来又导致大量种子或幼苗群定期或不稳定地从捕食者手中逃脱。
A high number of tree species, low density of adults of each species, and long distances between conspecific adults are characteristic of many low-land tropical forest habitats. I propose that these three traits, in large part, are the result of the action of predators on seeds and seedlings. A model is presented that allows detailed examination of the effect of different predators, dispersal agents, seed-crop sizes, etc. on these three traits. In short, any event that increases the efficiency of the predators at eating seeds and seedlings of a given tree species may lead to a reduction in population density of the adults of that species and/or to increased distance between new adults and their parents. Either event will lead to more space in the habitat for other species of trees, and therefore higher total number of tree species, provided seed sources are available over evolutionary time. As one moves from the wet lowland tropics to the dry tropics or temperate zones, the seed and seedling predators in a habitat are hypothesized to be progressively less efficient at keeping one or a few tree species from monopolizing the habitat through competitive superiority. This lowered efficiency of the predators is brought about by the increased severity and unpredictability of the physical environment, which in turn leads to regular or erratic escape of large seed or seedling cohorts from the predators.