Smithsonian Tropical Research Institute, Apartado, 0843-03092, Republic of Panama.
Department of Ecology and Evolutionary Biology, Tulane University, 400 Lindy Boggs, New Orleans, LA, 70118, USA.
New Phytol. 2013 Apr;198(1):241-251. doi: 10.1111/nph.12140. Epub 2013 Feb 13.
Fungal symbionts that live asymptomatically inside plant tissues (endophytes) can influence plant-insect interactions. Recent work has shown that damage by leaf-cutting ants, a major Neotropical defoliator, is reduced to almost half in plants with high densities of endophytes. We investigated changes in the phenotype of leaves that could influence ants' behavior to result in the reduction of foliar damage. We produced cucumber seedlings with high and low densities of one common endophyte species, Colletotrichum tropicale. We used the leaves in bioassays and to compare chemical and physical leaf characteristics important for ants' food selection. Ants cut about one-third more area of cucumber leaves with lower densities of endophytes and removed c. 20% more paper disks impregnated with the extracts of those leaves compared with leaves and disks from plants hosting the fungus. Colletotrichum tropicale colonization did not cause detectable changes in the composition of volatile compounds, cuticular waxes, nutrients or leaf toughness. Our study shows that endophytes changed leaf chemistry and suggests that compounds with relative low volatility released after leaf wounding are a major factor influencing foraging decisions by ants when choosing between plants with low or high endophyte loads.
生活在植物组织内无症状的真菌共生体（内生菌）可以影响植物-昆虫的相互作用。最近的研究表明，在内生菌密度较高的植物中，由切叶蚁造成的损害减少到几乎一半。我们研究了可能影响蚂蚁行为从而减少叶片损伤的叶片表型变化。我们用一种常见的内生真菌 Colletotrichum tropicale 生产了内生菌密度高和低的黄瓜幼苗。我们在生物测定和比较对蚂蚁食物选择很重要的化学和物理叶片特性中使用了这些叶片。与来自宿主真菌的叶片和圆盘相比，内生菌密度较低的黄瓜叶片被蚂蚁切割的面积约增加了三分之一，而从这些叶片中提取的浸有圆盘的纸张被蚂蚁取走的比例约增加了 20%。内生菌 Colletotrichum tropicale 的定植不会导致挥发性化合物、角质层蜡、营养物质或叶片韧性组成的可检测变化。我们的研究表明内生菌改变了叶片的化学成分，并表明在选择内生菌负荷低或高的植物时，受伤后释放的相对低挥发性化合物是影响蚂蚁觅食决策的一个主要因素。
