Department of Zoology, University of Florida, 32611, Gainesville, Florida.
J Chem Ecol. 1991 Aug;17(8):1593-610. doi: 10.1007/BF00984691.
Queen butterflies (Danaus gilippus) are generally considered unpalatable to predators because they sequester and store toxic cardenolides from their larval food plants. However, a major queen food plant in Florida, the asclepiadaceous vineSarcostemma clausum, is shown here to be a very poor cardenolide source, and queens reared on this plant contain no detectable cardenolide. A direct evaluation of queen palatability using red-winged blackbirds indicates thatS. clausum-reared butterflies are essentially palatable to these predators (85% of abdomens entirely eaten), indicating little protection from either cardenolides, other sequestered phytochemicals, or de novo defensive compounds. Wild-caught queens that presumably fed as larvae uponS. clausum and also had access to adult-obtained chemicals, such as pyrrolizidine alkaloids (PAs), were relatively palatable as well (77% of abdomens eaten); they did not differ significantly in palatability from the labreared butterflies. Together, these findings suggest that; (1)S. clausumfed queens are poorly defended against some avian predators, and (2) for the particular queen sample examined, PAs do not contribute substantially to unpalatability. The discovery thatS. clausum-feeding queens are essentially palatable is of additional significance because it compels a reassessment of the classic mimicry relationship between queen and viceroy butterflies. Viceroys have been shown recently to be moderately unpalatable; therefore, the established roles of model and mimic may be reversed in some cases.
帝王蝶（Danaus gilippus）通常被认为对捕食者来说是不可口的，因为它们从幼虫的食物植物中摄取并储存有毒的卡烯内酯。然而，佛罗里达州的一种主要的帝王蝶食物植物，夹竹桃科的藤本植物Sarcostemma clausum，被证明是一种很差的卡烯内酯来源，在这种植物上饲养的帝王蝶中没有检测到可检测的卡烯内酯。使用红翅黑鹂对帝王蝶的可食性进行直接评估表明，S. clausum 饲养的蝴蝶对这些捕食者基本上是可食用的（85%的腹部完全被吃掉），这表明它们几乎没有受到卡烯内酯、其他摄取的植物化学物质或新合成的防御化合物的保护。野生捕获的帝王蝶，推测幼虫时期以 S. clausum 为食，并且也可以获得成年后获得的化学物质，如吡咯里西啶生物碱（PAs），也相对可食用（77%的腹部被吃掉）；它们在可食性方面与实验室饲养的蝴蝶没有显著差异。这些发现表明：（1）以 S. clausum 为食的帝王蝶对一些鸟类捕食者的防御能力较差，（2）对于所检查的特定女王样本，PAs 并没有对不可口性做出重大贡献。S. clausum 喂养的帝王蝶基本上是可食用的这一发现具有额外的重要意义，因为它迫使人们重新评估女王和副王蝴蝶之间的经典拟态关系。最近已经表明副王蝴蝶的可食性适中；因此，在某些情况下，模型和模仿者的既定角色可能会被颠倒。
