Invasion of the Gran Canaria ravines ecosystems (Canary Islands) by the exotic species Acacia farnesiana

Abstract

The main objective of this study was to analyze if Acacia farnesiana, an introduced shrub from North and Central American tropics is spreading from areas in which it was introduced, and also to determine which animals operate as vectors for the shrub dispersion in the study area. The study site was located in southern Gran Canaria, one of the islands of the Canary Island archipelago. We selected six ravines in an area where approximately 40 plants of A. farnesiana were planted around 40 years ago. We analyzed the size structure of the population of A. farnesiana (density and biovolume) in the ravines, as well as its spatial distribution, in order to assess the degree of aggressiveness of this shrub in terms of spreading and expansion. Our results suggest that this shrub is spreading to new areas very quickly due to dispersion of seed by rabbits and an enhanced germination by the action of Mimoseste mimosae, a bruchid that decreases the germination period of the seed once it has separated from the fruit. Based on the results obtained in this study, we strongly suggest that managers of this area consider a management program to control further spread.