Degree of dietary specialization on furanocoumarin-containing hostplants in a newly invasive species, Depressaria depressana (Lepidoptera: Depressariidae)

Abstract The genus Depressaria (Lepidoptera: Depressariidae) mostly comprises specialist herbivores with varying capacity for detoxification of defensive phytochemistry. Depressaria depressana , a Eurasian moth recently introduced into North America, is a family-level specialist of the Apiaceae, whose hosts include more than a dozen species in multiple tribes; Depressaria radiella is a family specialist of Eurasian origin that feeds almost exclusively on species in the genera Pastinaca and Heracleum throughout its native and introduced range. In eastern North America it is found almost exclusively on Pastinaca sativa , an invasive European species, and Heracleum maximum , a native species. We determined whether differences in furanocoumarin metabolism exist between D. depressana and two isolated populations of D. radiella, feeding exclusively on either P. sativa or H. maximum . We also compared gravimetric estimates of efficiency to assess D. depressana larval performance on different diets. Both populations of D. radiella metabolized furanocoumarins at a greater rate than D. depressana . Although there was no difference in rates of metabolism of linear furanocoumarins in the two populations of D. radiella , individuals collected from H. maximum metabolized angular furanocoumarins more rapidly. The gravimetric assessments of performance revealed that D. depressana exhibited highest efficiencies consuming D. carota ; moreover, this species could survive consuming fruits of Z. aurea , an apiaceous species native to North America. Our preliminary phylogenetic analysis, building on an earlier morphological analysis, incorporates the mitochondrial cytochrome oxidase subunit 1 data, and revealed that the presence or absence of furanocoumarins is not a strong predictor of species-level evolution in Depressaria .