O papel das aves na dispersão de sementes da espécie exótica Schefflera actinophylla (Apiales, Araliaceae): potencial de invasibilidade

Abstract

Anthropogenic activities affect landscapes, biodiversity and ecosystem services. These actions impair animal/plant interactions, mainly involving frugivorous birds. The dispersion played by birds allows plant species to colonize distant areas, increasing the risk of invasion when an exotic species in involved. Exotic species are able to survive and grow, competing with native species resources and may cause changes in plant communities. In this research, we evaluated the potential for invasiveness of the exotic species Schefflera actinophylla (Cheflera), by analyzing bird-fruit interactions, phenophases and fruit offer, and seed germination. The study was carried out from September 2017 to September 2018 in both Carlos Alberto de Souza Park and Quinzinho de Barros Municipal Zoo, in the city of Sorocaba, state of São Paulo. We observed bird species, number and length of visits, number of ingested fruits, feeding behavior and fruit manipulation strategies. We considered the feeding categories of engulf, mash, pick, remove and drop. To estimate the germination percentage, we collected seeds from fruits of the focal trees and from feces of some captive birds. We compared seeds collected from green, immature, mature, fallen and from feces (Mimus saturninus and Turdus rufiventris). High percentage of germination (83.20 ± 8.16%) were observed in all treatments, and no germination for green fruit seeds. Phenophases in different individuals varied from 0 to 25% with the presence of some event. We consider as main potential seed dispersers, Pitangus sulphuratus, Turdus leucomelas and Megarynchus pitangua, with the predominant behavior of engulf the whole fruits (92% of the fruits), together with their frequency of visits (145 visits) and high number of ingested fruits (621 fruits). Feces of M. saturninus and T. rufiventris produced viable seeds, but with a lower percentage of germination. Natural regeneration was observed in the field, possibly from seeds dispersed by birds. Based on seed germination and presence of seedlings in the field, we concluded that Cheflera has a potential to be an invader, and its use in urban design should be avoided.