The phenolic glycosides tremulacin and salicortin found in quaking aspen, Populus tremuloides, and other members of the Salicaceae, are known to be toxic to larvae of the Eastern tiger swallowtail butterfly, Papilio glaucus, but not to the Canadian tiger swallowtail, P. canadensis. Larvae of the western tiger swallowtail, P. rutulus, were not killed nor were their growth rates suppressed when fed a mixture of tremulacin and salicortin on black cherry leaves. When the Salicaceae adapted P. rutulus penultimate instar larvae were fed a combination of the two phenolic glycosides and the esterase inhibitor (DEF S,S,S-tributylphosphorotrithioate), growth was reduced more than 50OJo compared to controls, and half of the larvae died before completing the instaL Our results indicate that esterase detoxification mechanisms are involved in the western tiger swallowtail, P. rutulus, as is also known to be the case for the northern tiger swallowtail, P. canadensis. It is not known whether the same esterase isozyme is involved in both species. From an evolutionary perspective such information could help resolve whether the Salicaceae-adapted swallowtails species are a monophyletic group (perhaps due to isolation in the Beringial Pleistocene glacial refuge of Alaska).
Scriber, J. Mark; Lindroth, Richard L.; and Nitao, James K.
"Toxic Phenolic Glycosides From Populus: Physiological Adaptations of the Western North American Tiger Swallowtail Butterfly, Papilio Rutulus (Lepidoptera: Papilionidae),"
The Great Lakes Entomologist, vol 24
Available at: https://scholar.valpo.edu/tgle/vol24/iss3/7