THE EVOLUTION OF DIET BREADTH - MONOPHAGY AND POLYPHAGY IN SWALLOWTAIL BUTTERFLIES

Much of the world's biodiversity has resulted from specialization of i nsect populations onto different plant species, partially through evol ution of preference in ovipositing females. Here I report an experimen tal analysis of how an oviposition preference hierarchy has evolved du ring the evolutionary diversification of an insect group to produce ta xa ranging from monophagous to polyphagous. Tests on the Papilio macha on group of swallowtail butterflies show that the preference hierarchy for plant species is evolutionarily dynamic within this species compl ex, yet constrained among most populations within species, creating a geographic mosaic of populations differing to various degrees in patte rns of host preference. The results indicate that different diet bread ths can evolve within a group of closely-related species through a com bination of conservatism in preference hierarchy among some population s, occasional but rare rearrangements in preference among others, corr elations in preference for some plant species, and availability of sim ilarly ranked hosts.