Smithsonian Tropical Research Institute, Unit 9100 Box 0948, DPO AA 34002, USA.
Ecology. 2011 Nov;92(11):2131-40. doi: 10.1890/10-2378.1.
The importance of vertebrates, invertebrates, and pathogens for plant communities has long been recognized, but their absolute and relative importance in early recruitment of multiple coexisting tropical plant species has not been quantified. Further, little is known about the relationship of fruit traits to seed mortality due to natural enemies in tropical plants. To investigate the influences of vertebrates, invertebrates, and pathogens on reproduction of seven canopy plant species varying in fruit traits, we quantified reductions in fruit development and seed germination due to vertebrates, invertebrates, and fungal pathogens through experimental removal of these enemies using canopy exclosures, insecticide, and fungicide, respectively. We also measured morphological fruit traits hypothesized to mediate interactions of plants with natural enemies of seeds. Vertebrates, invertebrates, and fungi differentially affected predispersal seed mortality depending on the plant species. Fruit morphology explained some variation among species; species with larger fruit and less physical protection surrounding seeds exhibited greater negative effects of fungi on fruit development and germination and experienced reduced seed survival integrated over fruit development and germination in response to vertebrates. Within species, variation in seed size also contributed to variation in natural enemy effects on seed viability. Further, seedling growth was higher for seeds that developed in vertebrate exclosures for Anacardium excelsum and under the fungicide treatment for Castilla elastica, suggesting that predispersal effects of natural enemies may carry through to the seedling stage. This is the first experimental test of the relative effects of vertebrates, invertebrates, and pathogens on seed survival in the canopy. This study motivates further investigation to determine the generality of our results for plant communities. If there is strong variation in natural enemy attack among species related to differences in fruit morphology, then quantification of fruit traits will aid in predicting the outcomes of interactions between plants and their natural enemies. This is particularly important in tropical forests, where high species diversity makes it logistically impossible to study every plant life history stage of every species.
脊椎动物、无脊椎动物和病原体对植物群落的重要性早已得到认可，但它们在热带植物多种共存物种早期繁殖中的绝对和相对重要性尚未量化。此外，由于热带植物中的天敌，有关果实特征与种子死亡率之间关系的了解甚少。为了研究脊椎动物、无脊椎动物和病原体对 7 种不同果实特征的冠层植物物种繁殖的影响，我们通过使用冠层围隔、杀虫剂和杀菌剂分别去除这些天敌，量化了果实发育和种子萌发因脊椎动物、无脊椎动物和真菌病原体而减少的程度。我们还测量了形态果实特征，假设这些特征可以介导植物与种子天敌之间的相互作用。脊椎动物、无脊椎动物和真菌根据植物物种的不同，对种子传播前的死亡率产生了不同的影响。果实形态解释了物种间的一些差异；种子周围果实较大且物理保护较少的物种，真菌对果实发育和萌发的负面影响更大，并且在整个果实发育和萌发过程中，由于脊椎动物的存在，种子存活率降低。在物种内，种子大小的变化也导致了天敌对种子活力的影响的变化。此外，在番樱桃属和大戟属中，在脊椎动物围隔内发育的种子和在杀菌剂处理下的种子的幼苗生长更高，这表明天敌的种子传播前效应可能会延续到幼苗阶段。这是首次在树冠中对脊椎动物、无脊椎动物和病原体对种子存活相对影响进行的实验测试。本研究进一步探讨了我们的结果对植物群落的普遍性。如果由于果实形态的差异，天敌的攻击在物种间存在强烈的变化，那么量化果实特征将有助于预测植物及其天敌之间相互作用的结果。在热带森林中，这一点尤为重要，在热带森林中，物种多样性很高，不可能对每个物种的每个植物生活史阶段进行逻辑研究。
