Influence of past land use and current human disturbance on non-native plant species on small Italian islands F. Pretto • L. Celesti-Grapow • E. Carli • C. Blasi Received: 1 October 2009 / Accepted: 28 February 2010 / Published online: 20 March 2010 Ó Springer Science+Business Media B.V. 2010 Abstract Biological invasions are regarded as one of the main drivers of habitat degradation in island ecosystems. Mediterranean islands have been sub- jected to a high degree of land conversion over the past 60 years, resulting in a massive reduction in the amount of rural land and the sprawl of tourist activities. The aims of this paper are to evaluate the current level of invasion of alien plant species in semi-natural vegetation types that have developed after the abandonment of agriculture and to analyze the relationships between non-native species, native flora, and environmental characteristics. Two Italian islands (Ponza and Ventotene) were surveyed using a random-stratified sampling. The occurrence and rel- ative cover of alien plant species were compared and separate analyses were performed for the native flora. Abundance patterns of both native and alien species were then studied in the light of the environmental and anthropogenic features. Although we found that some non-native species are extremely widespread, their relative cover at the plot level is low. Permu- tational Multivariate Analysis of Variance and Indi- cator Species Analysis revealed dissimilarities in the native species composition, while Mann–Whitney and Kruskal–Wallis tests showed differences in the ecological requirements (moisture, soil reaction, and nitrogen) of the native species pool. Canonical Correspondence Analysis pointed to the importance of the proximity to agricultural areas, human distur- bance, and past land management, particularly resid- ual terraces, in determining the difference between plant communities on the two islands. The results of our study suggest that traditional forms of agriculture may represent a key element for countering the establishment and spread of non-native plants in Mediterranean areas. Keywords Agriculture abandonment Á Mediterranean Basin Á Alien flora Á Ornamental introduction Á Plant invasion Á Terraces Abbreviations PERMANOVA Permutational multivariate analysis of variance ISA Indicator species analysis DCA Detrended correspondence analysis CCA Canonical correspondence analysis F. Pretto (&) Á L. Celesti-Grapow Á E. Carli Á C. Blasi Plant Biology Department, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy e-mail: francesca.pretto@uniroma1.it L. Celesti-Grapow e-mail: laura.celesti@uniroma1.it E. Carli e-mail: emanuela.carli@gmail.com C. Blasi e-mail: carlo.blasi@uniroma1.it 123 Plant Ecol (2010) 210:225–239 DOI 10.1007/s11258-010-9751-8