Processes and factors that affect regeneration and establishment of the invasive aquatic plant Cabomba caroliniana

Abstract

Many invasive macrophytes reproduce through fragments that are transported actively or passively to new habitats. On arrival, regeneration of fragments and colonisation of the new environment are critical steps in the invasion process. The effects of environmental and plant factors that potentially affect regeneration and colonisation success of Cabomba caroliniana A. Gray (Cabombaceae; cabomba, fanwort) were studied. C. caroliniana fragments had a very high regeneration potential that was not affected by nutrient availability. However, larger and apical fragments had higher establishment rate and regenerative growth. The coarseness of the substrate did not have any effect on establishment of C. caroliniana. Overall, even a single-node fragment had 50% establishment success when planted in substrate and this increased to 100% for fragments with two or more nodes. In contrast, free-floating propagules had only a 1–30% chance of colonisation, depending on the size of the fragment. It appears that propagule pressure is of less importance for the colonisation of C. caroliniana than the process of physical establishment in the substrate which acts as a bottleneck. Future work should address the specific processes that determine retention and establishment of propagules in the sediment.