EAB infestation levels were strongly correlated to latitudinal distribution of ash species
There was a significant positive correlation between the level of EAB infestation and latitude of ash trees (MLR: df =12,χ 2=28.63, P =0.0045) with all EAB infestations occurring in northern latitudes (Fig. 2a), while there was no significant correlation between EAB infestation level and ash tree altitude (MLR: df =9, χ 2=13.34,P =0.1477) (Fig. 2b). Similarly, there were no significant differences in EAB infestation levels among ash trees of different ages and sizes (MLR: df =4, χ 2=4.32,P =0.3650 for ash age; df =3,χ 2=2.13, P =0.5457 for ash size) (Fig. 2cd). In addition, there were no significant differences in EAB infestation levels among different habitats within ash species from the same origin category (MLR: df =2,χ 2=4.05, P =0.1322 for non-Asian ash;df =2, χ 2=1.43, P =0.4882 for native ash), while the EAB infestation levels in non-Asian ash trees were always more severe when compared to their native congeners within the same habitat (ANOVA: df =5,184, F =53.53,P <0.0001) (Fig. 3).