Banko P C, Cipollini M L, Breton G W, Paulk E, Wink M, Izhaki I
U.S. Geological Survey, Pacific Island Ecosystems Research Center, Kilauea Field Station, Hawaii National Park 96718, USA.
J Chem Ecol. 2002 Jul;28(7):1393-410. doi: 10.1023/a:1016248502927.
This study describes the chemical ecology of a tritrophic interaction among species endemic to the island of Hawaii, USA: a tree (Sophora chrysophylla: mamane), an endangered bird (Loxioides bailleui; palila), and moth larvae (Cydia spp.). Palila and Cydia both specialize on the seed embryos of mamane but avoid eating the seed coats. Palila actively seek out and feed mamane embryos and Cydia larvae to their nestlings. Because mamane embryos contain potentially toxic levels of alkaloids, including broadly toxic quinolizidine alkaloids, and because insects often sequester alkaloids from their food plants, we focus on the questions of why palila forage upon mamane embryos and why they supplement their diet with Cydia larvae. Our data show that mamane embryos contain high amounts of potentially toxic alkaloids, but are well balanced nutritionally and contain lipids, carbohydrates, proteins, amino acids, and minerals at levels that are likely to be sufficient for maintenance and breeding. Mamane seed coats contain lower levels of alkaloids and nutrients, somewhat higher levels of phenolics, and much higher levels of nondigestible fiber. Taken together, these results suggest that palila have evolved tolerance to high levels of alkaloids and that they forage upon embryos primarily because of their availability in the habitat and high nutritional reward. Our data also suggest that Cydia are used by palila because they are readily accessible, nontoxic, and nutritious; the larvae apparently do not sequester alkaloids while feeding upon mamane seeds. Our results are interpreted with respect to the likelihood of current and historical coadaptive responses in this ecologically isolated and simplified island setting.
一种树（金叶槐：马马内树）、一种濒危鸟类（贝利氏管舌雀；帕利拉雀）和蛾幼虫（苹果蠹蛾属）。帕利拉雀和苹果蠹蛾都专门以马马内树的种子胚为食，但不吃种皮。帕利拉雀会主动寻找马马内树的胚并喂给雏鸟，也会喂苹果蠹蛾幼虫。由于马马内树的胚含有潜在毒性水平的生物碱，包括具有广泛毒性的喹嗪类生物碱，且昆虫常常从其取食的植物中积累生物碱，我们关注的问题是，为什么帕利拉雀以马马内树的胚为食，以及它们为什么用苹果蠹蛾幼虫来补充饮食。我们的数据表明，马马内树的胚含有大量潜在有毒生物碱，但营养成分均衡，含有脂质、碳水化合物、蛋白质、氨基酸和矿物质，其含量可能足以维持生存和繁殖。马马内树的种皮生物碱和营养成分含量较低，酚类物质含量略高，不可消化纤维含量高得多。综合来看，这些结果表明，帕利拉雀已经进化出对高含量生物碱的耐受性，它们以胚为食主要是因为胚在栖息地中易于获取且营养回报高。我们的数据还表明，帕利拉雀食用苹果蠹蛾是因为它们易于获取、无毒且营养丰富；幼虫在取食马马内树种子时显然不会积累生物碱。我们结合当前和历史上在这个生态隔离且简化的岛屿环境中共同适应反应的可能性来解释我们的结果。
