Center for Industrial Ecology, School of Forestry and Environment, Yale University, New Haven, CT, USA.
J Chem Ecol. 2012 Jan;38(1):88-99. doi: 10.1007/s10886-011-0052-z. Epub 2012 Jan 11.
Ant-plant interactions often are mediated by extrafloral nectar (EFN) composition that may influence plant visitation by ants. Over a 300 km range in the Indian Western Ghats, we investigated the correlation between the EFN composition of the myrmecophytic ant-plant Humboldtia brunonis (Fabaceae) and the number and species of ants visiting EFN. EFN composition varied among H. brunonis populations and between plant organs (floral bud vs. young leaf EFN). In general, EFN was rich in sugars with small quantities of amino acids, especially essential amino acids, and had moderate invertase activity. In experiments at the study sites with sugar and amino acid solutions and with leaf or floral bud EFN mimics, dominant EFN-feeding ants differentiated between solutions as well as between mimics. The castration parasite Crematogaster dohrni (northern study site) was the least selective and did not exhibit any clear feeding preferences, while the largely trophobiont-tending non-protective Myrmicaria brunnea (middle study site) preferred higher sucrose concentrations and certain essential/non-essential amino acid mixtures. The mutualistic Technomyrmex albipes (southern study site) preferred sucrose over glucose or fructose solutions and consumed the leaf EFN mimic to a greater extent than the floral bud EFN mimic. This young leaf EFN mimic had low sugar concentrations, the lowest viscosity and sugar:amino acid ratio, was rich in essential amino acids, and appeared ideally suited to the digestive physiology of T. albipes. This preference for young leaf EFN may explain the greater protection afforded to young leaves than to floral buds by T. albipes, and may also help to resolve ant-pollinator conflicts. The differential response of dominant ants to sugar, amino acids, or solution viscosity suggests that plants can fine-tune their interactions with local ants via EFN composition. Thus, EFN can mediate local partner-choice mechanisms in ant-plant interactions.
在印度西高止山脉的 300 公里范围内，我们研究了共生蚁植物 Humboldtia brunonis（豆科）的外分泌蜜腺（EFN）组成与访问 EFN 的蚂蚁数量和种类之间的相关性。EFN 组成在 H. brunonis 种群之间以及植物器官（花芽与嫩叶 EFN）之间存在差异。一般来说，EFN 富含糖，含有少量氨基酸，特别是必需氨基酸，并且具有中等的转化酶活性。在研究地点进行的实验中，使用糖和氨基酸溶液以及叶或花芽 EFN 模拟物，优势 EFN 取食蚂蚁能够区分溶液和模拟物。绝育寄生虫 Crematogaster dohrni（北部研究地点）是最不具选择性的，没有表现出任何明显的取食偏好，而主要是营养生物倾向的非保护 Myrmicaria brunnea（中部研究地点）则更喜欢较高的蔗糖浓度和某些必需/非必需氨基酸混合物。互利共生的 Technomyrmex albipes（南部研究地点）更喜欢蔗糖而不是葡萄糖或果糖溶液，并且消耗叶 EFN 模拟物的程度大于花芽 EFN 模拟物。这种嫩叶 EFN 模拟物的糖浓度较低，粘度和糖：氨基酸比最低，富含必需氨基酸，并且似乎非常适合 T. albipes 的消化生理学。对嫩叶 EFN 的这种偏好可以解释 T. albipes 对嫩叶的保护程度大于对花芽的保护程度，并且也有助于解决蚂蚁-传粉者冲突。优势蚂蚁对糖、氨基酸或溶液粘度的不同反应表明，植物可以通过 EFN 组成来微调它们与当地蚂蚁的相互作用。因此，EFN 可以介导蚂蚁-植物相互作用中的本地伙伴选择机制。
