Differential Primary Seed and Fruit Dispersal Mechanisms and Dispersal Biomechanics in Invasive Dehiscent and Indehiscent-Fruited Lepidium Species

Abstract

This study explores primary dispersal, which involves diaspores’ detachment directly from mature plants, and secondary dispersal, which encompasses any further dispersal occurring after the primary dispersal. A comparison of the primary dispersal vectors of the invasive dehiscent fruit producing Lepidium campestre and the indehiscent fruit producing Lepidium draba was conducted. These vectors were examined in relation to the native and introduced distribution ranges of the species, and regarding biomechanical forces required detaching the fruits from mature plants. Our findings reveal that rainfall and animal contact serve as primary dispersal vectors for Lepidium campestre, while animal contact is rarely involved in primary dispersal of Lepidium draba. Primary dispersal is more important for Lepidium campestre than Lepidium draba, which requires significantly greater force for fruit detachment. While previous studies indicate wind and rainfall as major secondary dispersal vectors for Lepidium draba, our results suggest secondary dispersal via mucilage on seeds is more crucial for this species. The strong reliance of Lepidium draba on secondary dispersal, enabling long-distance dispersal, could contribute to its invasion success, linking it to the species’ geographic distribution. Understanding these different dispersal strategies is essential for effective management of invasive species.