Recruitment of two Opuntia species invading abandoned olive groves

In Europe, many agricultural areas are now abandoned and hence can be invaded by exotic species. The abundance and spatial distribution patterns of two Opuntia species were studied in old olive groves in the Parc Natural del Cap de Creus, Catalonia (Spain). Seedling recruitment (97.3% and 51.5% of juveniles for O. maxima and O. stricta, respectively) was higher than recruitment by cladodes. O. maxima had more seedlings recruited beneath olive trees and beneath Opuntia adults than expected. Most O. stricta seedlings were also located beneath Opuntia adult plants. However, although most seedlings were recruited beneath Opuntia, some (10-30%) were found away from putative parental plants. This may be due to seed dispersal by birds and wild boars. Seeds dispersed by wild boars were not significantly more viable than seeds from intact fruits. Seedlings grow very slowly but have a high survival rate. In conclusion, Opuntia seedling recruitment is very successful and ensures the persistence of these species within old olive groves. Consequently, it prevents restoration from an agricultural land-use back to the native community. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.