Wenny D G, Levey D J
Department of Zoology, 223 Bartram Hall, P.O. Box 118525, University of Florida, Gainesville, FL 32611-8525, USA.
Proc Natl Acad Sci U S A. 1998 May 26;95(11):6204-7. doi: 10.1073/pnas.95.11.6204.
A fundamental goal of plant population ecology is to understand the consequences for plant fitness of seed dispersal by animals. Theories of seed dispersal and tropical forest regeneration suggest that the advantages of seed dispersal for most plants are escape from seed predation near the parent tree and colonization of vacant sites, the locations of which are unpredictable in space and time. Some plants may gain in fitness as a fortuitous consequence of disperser behavior if certain species of dispersers nonrandomly place seeds in sites predictably favorable for seedling establishment. Such patterns of directed dispersal by vertebrates long have been suggested but never demonstrated for tropical forest trees. Here we report the pattern of seed distribution and 1-year seedling survival generated by five species of birds for a neotropical, shade-tolerant tree. Four of the species dispersed seeds to sites near the parent trees with microhabitat characteristics similar to those at random locations, whereas the fifth species, a bellbird, predictably dispersed seeds under song perches in canopy gaps. The pattern of seedling recruitment was bimodal, with a peak near parent trees and a second peak, corresponding to bellbird song perches, far (>40 m) from parent trees. Seedling survival was higher for seeds dispersed by bellbirds than by the other species, because of a reduction in seedling mortality by fungal pathogens in gaps. Thus, bellbirds play a significant role in seed dispersal by providing directed dispersal to favorable sites and therefore may influence plant recruitment patterns and species diversity in Neotropical forests.
植物种群生态学的一个基本目标是了解动物传播种子对植物适合度的影响。种子传播和热带森林更新理论表明，对大多数植物而言，种子传播的优势在于逃离母树附近的种子捕食以及在时空上位置不可预测的空地上定殖。如果某些传播者物种将种子非随机地放置在可预测地有利于幼苗建立的地点，一些植物可能会因传播者行为的偶然结果而在适合度上有所增加。脊椎动物的这种定向传播模式长期以来一直被提及，但从未在热带森林树木中得到证实。在此，我们报告了五种鸟类对一种新热带耐荫树木产生的种子分布模式和一年生幼苗存活情况。其中四个物种将种子传播到母树附近具有与随机位置相似微生境特征的地点，而第五个物种，一种钟雀，可预测地将种子传播到林冠空隙中其歌声停歇处下方。幼苗补充模式是双峰的，在母树附近有一个峰值，另一个峰值对应钟雀歌声停歇处，距离母树较远（>40米）。由于林冠空隙中真菌病原体导致的幼苗死亡率降低，钟雀传播的种子的幼苗存活率高于其他物种。因此，钟雀通过向有利地点提供定向传播在种子传播中发挥着重要作用，进而可能影响新热带森林中的植物补充模式和物种多样性。
