The danger of non-native gardens: risk of invasion by Schefflera arboricola associated with seed dispersal by birds

Abstract

The success of invasion by non-native species can be influenced by positive interactions established in the area of introduction. For instance, seed dispersal by birds can increase seed rain, seed germination, and, as a consequence, the probability of establishment of new invasion foci. Schefflera arboricola, an ornamental shrub with fruits largely consumed by birds, is invasive in several countries. To our knowledge, this is the first research project on mechanisms that might explain the success of S. arboricola in areas where it is invasive. The main aim of this study was to assess the invasiveness of S. arboricola associated with seed dispersal by birds. Fruit availability and frugivory interactions with local birds were registered and the germination percentage of seeds not consumed by birds was compared to the germination of seeds collected from bird feces. Our results show that frugivory and seed dispersal by native birds increase the establishment of S. arboricola. In addition, intrinsic species traits such as extended flowering and fruiting, high percentage of seed germination, early germination due to frugivory, and ability to establish in different microhabitats facilitate invasion by S. arboricola. Given the intensive horticultural use of S. arboricola and seed dispersal interactions with generalist birds, there is an imminent risk of invasion in forest remnants close to wherever S. arboricola is cultivated. We recommend that adult plants of S. arboricola are eliminated from gardens and semi-natural areas close to protected areas as a prevention measure to avoid invasions and impacts on natural habitats.