Table 2 Mean foliar nutrient concentrations and element ratios of Wve randomly chosen plants Control 417 § 2.6 23.5 § 1.9 4.15 § 0.27 18.3 § 1.49 5.6 § 0.2 Glomus intraradices Glomus mosseae 410 § 1.0 23.4 § 1.6 4.25 § 0.07 17.8 § 1.13 5.5 § 0.3 414 § 1.0 21.4 § 1.1 3.73 § 0.15 19.6 § 1.05 5.7 § 0.2 272 Foliar nutrients C (mg g¡1) N (mg g¡1) P (mg g¡1) C/N ratio N/P ratio Values are given as the mean § standard error (SE) There were no signiWcant diVerences due to AMF inoculation Table 3 Results of ANCOVA on aphid population growth rates and of the analysis of deviance on the proportion of aphid populations with negative growth rates * SigniWcant at P < 0.05 Orthogonal contrasts are calcu- lated for AMF treatments (see Materials and methods for details) Source of variation Initial plant size Block Parasitoid presence AMF AMF vs. control Intra vs. moss Residuals df 1 9 1 2 1 1 75 dry weight 53.7 § 3.9 and 54.0 § 2.6 g for G. intrara- dices and G. mosseae, respectively) than on non-mycorrhi- zal plants (43.5 § 4.1 g, Fig. 2; Table 4). Additionally, the development of parasitoids was signiWcantly faster in the AMF treatments (mean developmental time 17.0 § 0.2 and 16.8 § 0.2 days for G. intraradices and G. mosseae, respectively) than in the control treatment (17.7 § 0.2 days; Table 4). There was no signiWcant diVerence in parasitoid dry weight and developmental time between the two AMF species. Sex ratio had a signiWcant eVect on dry weight, with females being heavier than males, but there was no diVerence between the sexes in terms of development time. The opposite was true for the number of aphids, which had a signiWcant impact on the developmental time of emerging wasps, but not on parasitoid dry weight (Table 4). A comparison of sex-speciWc mean values for dry weight at eclosion and development time in the control and in the two AMF treatments showed rather uniform responses of males and females in the control and G. intraradices treat- ments, with a better performance in the latter (Fig. 2). In contrast, A. rhopalosiphi expressed a clear sex-speciWc reaction in the G. mosseae treatment, with males develop- ing faster and females getting heavier. Nevertheless, there was no signiWcant diVerence in parasitoid sex ratio (mean 49 § 15, 37 § 10, and 51 § 13% females in control, G. intraradices, and G. mosseae treatments, respectively, F2,22 = 0.47, P = 0.63). The proportion of adult aphids among mummies was also not signiWcantly diVerent 123 Oecologia (2009) 160:267–277 F value 3.78 0.53 1.79 0.87 0.25 P value 0.06 0.60 0.21 0.44 0.78 P value 0.07 0.005* 0.69 0.05* 0.01* 0.90 MS 23.00 154.11 71.35 280.84 491.36 60.53 86.59 Aphid population growth rates Populations with negative growth rates F value P value Log likely-hood ratio 0.27 1.78 0.82 3.24 5.67 0.70 0.61 0.09 0.37 0.04* 0.02* 0.41 3.12 23.46 0.16 6.01 45.47 42.50 Fig. 2 Mean parasitoid dry weight (+SE) plotted against mean para- sitoid developmental time (+SE) for both sexes separately. Circles Non-mycorrhizal control, squares plants inoculated with Glomus intraradices, diamonds plants inoculated with G. mosseae. Open and closed symbols represent data for female and male parasitoids, respec- tively between the AMF treatments (mean 27 § 8, 51 § 8, and 50 § 12% in control, G. intraradices, and G. mosseae treat- ments, respectively, F2,21 = 0.23, P = 0.80). The rate of parasitism (expressed as intercept in Fig. 3) was signiWcantly diVerent between the G. intraradices (15.9 § 3.7%) and the two other treatments (6.6 § 1.6 and 6.3 § 1.0% in control and G. mosseae treatments, respec- tively, P = 0.007). However, MA regression showed no