Habitat Preference Within Its Native Range and Allelopathy of Garlic Mustard Alliaria petiolata

Abstract

Even though Alliaria petiolata is a globally important invasive plant, for Europe it is a native humble understory species. I studied the population characteristics of A. petiolata in its native range (NE Slovenia) by evaluating its demographic structure (e.g. population size, density, plant fruit production) and herbivory damage in different habitats (forest understorey, forest edge, ruderal site). Moreover I tested the allelopathic potential of fresh A. petiolata leaves and roots on garden cress Lepidium sativum germination and seedling development. I performed bioassays with aqueous extracts and took a first step toward testing the presence of volatile potentially allelopathic compounds. The results showed that A. petiolata populations can become established at disturbed sites, even such without a tree canopy, but dense stands can be found only at disturbed forest edges. The bioassays confirmed the presence of A. petiolata aqueous and volatile allelochemicals in leaves and roots. Germination was suppressed more by volatiles, showing that allelopathy can act via volatile compounds and further suggesting their antifungal effects. The results allow predicting that the success of A. petiolata invasion in a non-native range might rely on its variable habitat tolerance (not being a strict ruderal species) and allelopathy.