Efecte de la fauna frugívora sobre el poder invasiu de les espècies vegetals exòtiques de fruit carnós

Abstract

Invasive species cause economic and ecological losses. In this study we attempt to obtain biological and ecological information about two invasive species, Pyracantha coccinea, and Lonicera japonica which produce fleshy fruits and interact ecologically with frugivorous fauna in order to be dispersed by endozoochory, or in the antagonist ecological relationship of seed depredation. Here we determine the effect of the frugivores over the invasion potential of these two species, and we assess how to improve invasion species control management in the Puda Forest in Banyoles. In our study we excluded any branches covered by mosquito or insect nets, which would have made it impossible for the fruits on the branch to be consumed, and we used the net-free branches (our control group) to determine the fruit loss (fruit removal) from the branches. Additionally, we carried out a census of the bird and micromammal communities, in order to determine what kind of frugivores there were in the study zone i.e. either mutualist or antagonist. The results conclude that because a huge percentage of fruits are consumed by frugivores, they have a significant effect on the dispersion and depredation of seeds in the both species. If frugivores did not interact with the plants, the fruits would stay on the branches for almost 8 months even after reaching their peak ripeness. However, we have to take in account that in the census we find legitimate frugivores, pulp eaters and seed depredators; therefore not every fruit that is consumed benefits that plant itself. Finally, the study proposes two different types of management programmes. The first one is for the Puda Forest, and involves eliminating the exotic plants which are to be found on the edge of the forest, in other words those which have taken over the greatest area and consequently have more opportunities to reproduce and disperse their seeds. Conversely, those found in the middle of the forest will grow slowly and will die thanks to the shade and the competition the adult ashes provide. The second management strategy is to establish a programme to create and monitor an invasive-plant-free forest (like the Puda Forest) in an abandoned crop field