Comparación de la flora exótica vascular en sistemas de islas continentales: Cerde a (Italia) y Baleares (Espa a)

This paper provides a comparison of the vascular exotic flora of Sardinia and that of the Balearic Islands, both territories belonging to the Western Mediterranean biogeographic subregion. The study has recorded 531 exotic taxa in Sardinia (18.8% of the total flora) while 360 (19%) in the Balearic Islands; 10 are new to Sardinia (3 of which for Italy) and 29 to the Balearic Islands. The alien flora of Sardinia is included in 99 families; Fabaceae is the richest (49 taxa), followed by Poaceae (33) and Asteraceae (31) while in the Balearic Islands in 90 families, with a predominance of Fabaceae (32), Asteraceae (31) and Poaceae (27). The comparison of the biological spectra reveals that in Sardinia phanerophytes are the most represented in Sardinia and therophytes in the Balearic Islands. A detailed analysis shows that most of the exotic taxa (246) are shared by both territories with a clear dominance of neophytes rather than archaeophytes. A study of the geographical origin shows supremacy of the American element over the Mediterranean. The majority of introduced exotic taxa are a result of intentional human introductions (76% SA, 77% BL), mainly for ornamental use (43% SA, 45% BL). The most occupied habitats are the semi-natural, agricultural and synanthropic for both territories, but attending to invasive plants, coastal habitats in Sardinia and wetlands in the Balearic Islands are the most sensitive. A part of the work deals with the causes of fragility and low resilience of the different habitats. Se presenta un estudio comparativo de la flora vascular exótica de Cerde a y de las Baleares, dos sistemas insulares pertenecientes a la subregión biogeográfica Mediterránea Occidental. En Cerde a se han contabilizado 531 táxones exóticos (18,8% del total de su flora), mientras que en las Baleares 360 (19%), siendo 10 citas nuevas para Cerde a (3 de las cuales para Italia) y 29 para Baleares. La flora exótica de Cerde a está incluida en 99 familias, y Fabaceae es la más rica (49 táxones), seguida por Poaceae (33) y Asteraceae (31), frente a 90 familias para las Baleares, con predominio de Fabaceae (32), Asteraceae (31) y Poaceae (27). Se han encontrado diferencias respecto a los tipos biológicos, con un predominio de los fanerófitos en Cerde a y de los terófitos en las Baleares. Un análisis detallado muestra que buena parte de estos táxones (246) son compartidos por ambos territorios, así como una dominancia de los neófitos frente a los arqueófitos. Respecto al origen geográfico, ambos territorios presentan una preeminencia del elemento americano sobre el m