Fijian swallowtail butterfly Papilio schmeltzi (Papilionidae: Lepidoptera) shows clear preference–performance relationships on both native and exotic host plants

The swallowtail butterfly Papilio schmeltzi is endemic to the Fiji Islands. To date, P. schmeltzi larvae and eggs have been found exclusively on a native Fijian shrub, Micromelum minutum , even though numerous other seemingly suitable native and exotic species of Rutaceae now occur in its Fijian forest habitat. This study used outdoor cages and laboratory studies to examine oviposition preferences and larval development of P. schmeltzi on four species of Rutaceae: the native species Micromelum minutum and Euodia hortensis and the introduced species Murraya koenigii and Citrus reticulata . The female oviposition preference sequence was the same as that for larval feeding preference, which ran, from most preferred, as Micromelum minutum  >  C. reticulata   >   Murraya koenigii  >  E. hortensis . The survival of the first and fifth instar larvae was highest (≥80%) when maintained on leaves of M. minutum and C. reticulata and lowest when reared on Murraya koenigii (≤20%) and E. hortensis (≤4%). Of the two preferred host plants, P. schmeltzi larvae gained weight more quickly, consumed a larger area of leaf and pupated earlier when reared on the natural host Micromelum  minutum compared with the exotic C. reticulata . In quantitative nutritional studies, the consumption rate of leaf material, and the relative growth rate of the P. schmeltzi larvae, was highest when reared on Micromelum minutum compared with C. reticulata , although the efficiency of converting leaf biomass into larval biomass was highest when reared on C. reticulata , especially in the later instars. Overall, the results of our study indicate the plants on which P. schmeltzi females choose to lay eggs are not restricted to native Fijian plant species but are appropriate when viewed in terms of subsequent larval preferences, survival and growth rate.