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Pre-adaptations and shifted chemical defences provide Buddleja davidii populations with high resistance against antagonists in the invasive range

Pankoke, Helga, Tewes, Lisa Johanna, Matties, Stephanie, Hensen, Isabell, Schädler, Martin, Ebeling, Susan, Auge, Harald, Müller, Caroline
Biological invasions 2019 v.21 no.2 pp. 333-347
Buddleja davidii, Scrophulariaceae, antagonists, chemical compounds, chemical defenses, colonizing ability, ecological invasion, fractionation, fungi, herbivores, indigenous species, invasive species, leaves, shrubs, virulent strains, China
The local invasion success of invasive plants can be strongly influenced by reduced antagonist pressure and changes in resistance-mediating traits, but information about comprehensive metabolic backgrounds of native versus invasive populations and their functions is lacking. We examined the defence potential of ten native (Chinese) and ten invasive (European) populations of the shrub Buddleja davidii (Scrophulariaceae) grown in a common garden in the invasive range. We compared the chemical defence arsenal of these plant populations, scored their herbivore damage in the field and determined effects on a generalist herbivore species in the laboratory. Moreover, we isolated compounds that mediate resistance against two potential generalist herbivore species and a pathogenic fungus using bioassay-guided fractionation. Metabolic fingerprinting revealed that invasive populations were chemically very similar to one native population (Mupingzhen, Sichuan Province), which may indicate the geographic region from where the species was introduced. Herbivore damage and herbivore performance were reduced on plants of invasive populations. Different chemical compounds provided distinct resistance against the herbivore and fungus species. Based on our results we suggest that the diverse cocktail of chemical compounds, potentially together with physical leaf features, may provide this plant species with an effective defence arsenal against antagonists. In particular, advantageous pre-adaptations and/or shifted profiles of the chemical bouquet may contribute to the success of invasive plants.