Departamento de Biología, Universidad Nacional de Colombia, Ciudad Universitaria, Bogotá, Colombia.
Department of Entomology, Cornell University, Ithaca, New York, United States of America.
PLoS One. 2017 Dec 6;12(12):e0188408. doi: 10.1371/journal.pone.0188408. eCollection 2017.
Plant responses induced by herbivore damage can provide fitness benefits, but can also have important costs due to altered interactions with mutualist pollinators. We examined the effects of plant responses to herbivory in a hummingbird-pollinated distylous shrub, Palicourea angustifolia. Through a series of field experiments we investigated whether damage from foliar herbivores leads to a reduction in fruit set, influences floral visitation, or alters floral traits that may influence pollinator preference or pollinator efficiency. Foliar herbivory by a generalist grasshopper led to reduced fruit set in branches that were directly damaged as well as in adjacent undamaged branches on the same plant. Furthermore, herbivory resulted in reduced floral visitation from two common hummingbird species and two bee species. An investigation into the potential mechanisms behind reduced floral visitation in induced plants showed that foliar herbivore damage resulted in shorter styles and lower nectar volumes. This reduction in style length could reduce pollen deposition between different floral morphs that is required for optimal pollination in a distylous plant. We did not detect any differences in the volatile blends released by damaged and undamaged branches, suggesting that foliar herbivore-induced changes in floral morphology and rewards, and not volatile blends, are the primary mechanism mediating changes in visitation. Our results provide novel mechanisms for how plant responses induced by foliar herbivores can lead to ecological costs.
植物对食草动物损害的反应可以提供适应益处，但由于与互惠共生传粉者的相互作用发生改变，也可能带来重要的代价。我们研究了食草动物损害对蜂鸟传粉的二型花柱灌木 Palicourea angustifolia 植物的影响。通过一系列野外实验，我们调查了叶部食草动物的损害是否会导致结实减少，是否会影响花朵访花，或是否会改变可能影响传粉者偏好或传粉者效率的花朵特征。一种草食性蚱蜢对叶片的一般性损害，导致了直接受损枝条以及同一植株上相邻未受损枝条的结实减少。此外，食草损害还导致两种常见的蜂鸟和两种蜜蜂物种的访花减少。对诱导植物中访花减少的潜在机制的调查表明，叶片食草动物的损害导致花柱变短，花蜜量减少。这种花柱长度的缩短可能会减少在二型花柱植物中优化授粉所需的不同花型之间的花粉沉积。我们没有检测到受损和未受损枝条释放的挥发性混合物有任何差异，这表明花朵形态和奖励的叶片食草动物诱导变化，而不是挥发性混合物，是介导访花变化的主要机制。我们的研究结果为叶片食草动物诱导的植物反应如何导致生态代价提供了新的机制。
