Chuva de sementes: dinâmica de dispersão na presença de uma espécie exótica invasora, Artocarpus heterophyllus Lam. (jaqueira), no Parque Estadual da Ilha Grande, Angra dos Reis, RJ

Abstract

Seed rain is the dynamic seed dispersion of a forest, representing what reaches the ground by means of dispersal agents. In the community of plants, the predominant dispersal syndromes allow the understanding of the successional stages, structure and level of conservation of vegetation. The jackfruit tree, Artocarpus heterophyllus, was introduced In Brazil during the colonial period. The jackfruit invasion could be impairing the dispersion of native species, since the dispersion of native seeds may be affected by the spatial distribution of plants and by the barriers present in the environment. The study aimed to verify whether the jacket, because it is an exotic invasive species, influences the composition and abundance of seed rain. The study was conducted in the Atlantic forest, located in the State Park of Ilha Grande, RJ. Were used to collect seed rain 16 collectors with 1m of diameter in areas with (C) and without (S) jackfruit, totaling 32 collectors checked monthly during one year of collection. The analyses performed in this work were ANOVA, Regression and NMDS, in order to verify if the presence of jackfruit would be influencing the seed rain as for richness, composition and abundance. In the material from 320 samples, we observed 166.376 seeds, corresponding to 84 morphospecies, 29 species belonging to 25 families and 55 unidentified morphospecies. The areas without (S) jackfruit showed greater richness, low abundance and diversity. In areas with jackfruit (C) the abundance of native seeds showed a negative relationship with the abundance of the exotic in the plots. The composition and abundance of diaspores had no clear separation between areas with and without jackfruit, as showed in the NMDS. However, when analyzing the first axis of NMDS with the abundance of jackfruit trees in the grids, the relationship with the number abundance of jackfruit. The main dispersion syndromes observed in work related species which have been identified, and were anemochory and zoochory, the latter being the most abundant syndrome among areas. The results showed that the presence of jackfruit tree affects the seed rain in Ilha Grande State Park. A lower richness and abundance of native seeds reach the ground in areas with jackfruit (C) affecting the succession and dynamics of the forest.