Figure 1.
Host plant preferences of a specialist and generalist moth species
(A and B) Attraction of female T. jacobaeae moths (A) and female M. brassicae moths (B) to the odors of undamaged native and invasive Jacobaea vulgaris genotypes and two controls (blank) in a four-arm olfactometer (n = 5 for Australia [AUS], n = 5 for New Zealand [NZ], n = 8 for Western North America [WNA], and n = 18 for Europe). Values are means of number of moths choosing an olfactometer arm ± SE of 18 replicates for both moth species. 75% and 86% of the T. jacobaeae and M. brassicae, respectively, made a choice. Generalized linear mixed models (GLMMs) with a Poisson error distribution: (A) origin: χ2(2) = 64.813, p < 0.001; range within origin: χ2(2) = 0.724, p = 0.70; (B) origin: χ2(2) = 88.348, p < 0.001; range within origin: χ2(2) = 1.324, p = 0.52. Different letters indicate significant differences among treatments at p < 0.05 with a Tukey post hoc test, whereas ns above the three invasive ranges represents no significant difference among the three invasive ranges.
(C and D) Proportion of T. jacobaeae (C) and M. brassicae (D) females that chose an undamaged native J. vulgaris over an undamaged invasive J. vulgaris in the olfactometer assay plotted against the differences in the amounts of constitutive plant volatiles (CPVs) released between the invasive and native J. vulgaris of the same pair. Logistic regressions (binomial GLM): (C) χ2(1) = 7.635, p = 0.006; (D) χ2(1) = 28.147, p < 0.001. The solid line indicates the predictions from the model and the dotted lines the confidence intervals of the predictions.
See also Figures S1, S3, and S4A and Table S2.