title: Palatability of aposematic queen butterflies (Danaus gilippus) feeding onSarcostemma clausum (Asclepiadaceae) in Florida.
abstract: 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.
authors.affiliation: Department of Zoology, University of Florida, 32611, Gainesville, Florida.
authors.forename: D B
authors.initials: DB
authors.lastname: Ritland