A Model Without a Mimic: Aristolochic Acids from the California Pipevine Swallowtail, Battus philenor hirsuta, and Its Host Plant, Aristolochia californica

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The pipevine swallowtail, Battus philenor, feeds exclusively on plants in the genus Aristolochia, many of which are known to contain the toxic alkaloids collectively known as aristolochic acids. Pipevine swallowtails sequester these compounds and use them for their own defense against predators. Numerous palatable butterflies are involved in Batesian mimicry complexes with B. philenor over its range. The California subspecies of the pipevine swallowtail, B. philenor hirsuta, has no mimics. Analysis of the butterfly and its only host plant, Aristolochia californica, indicate that both contain aristolochic acid. Aristolochic acid (I) and (II) are the primary aristolochic acids found in A. californica. The highest concentration of aristolochic acids was found in the flowers, which bloom before B. philenor emerges. Concentrations of aristolochic acids decreased in the leaves but not in stem tissue over the course of the season. Butterflies contained primarily aristolochic acid (I). Aristolochic acid content of individuals from Arizona, which are involved in mimicry complexes, did not differ from California populations. Thus, lack of California mimics cannot be attributed to low aristolochic acid content of the model.