Comparación de la flora exótica vascular en sistemas de islas continentales: Cerdeña (Italia) y Baleares (España)

Abstract

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.Keywords: alien species, biogeography, conservation, invasions, Mediterranean. Se presenta un estudio comparativo de la flora vascular exótica de Cerdeña y de las Baleares, dos sistemas insulares pertenecientes a la subregión biogeográfica Mediterránea Occidental. En Cerdeña 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 Cerdeña (3 de las cuales para Italia) y 29 para Baleares. La flora exótica de Cerdeña 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 Cerdeña 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 mediterráneo. En referencia a las vías de introducción, la mayor parte de los táxones ha sido introducida por parte del hombre de forma intencionada (76% SA, 77% BL) en particular para uso ornamental (43% SA, 45% BL). Los hábitats más afectados son los seminaturales, agrícolas y sinantrópicos en ambos territorios, aunque atendiendo a la flora invasora, son los litorales los más sensibles ...

Comparative Analysis of the Alien Vascular Flora of Sardinia and Corsica

“…These data are consistent with those observed in other contexts of the Mediterranean islands, e.g., the Balearic Islands (19%, Podda et al, 2010), and are significantly higher than those reported for Sicily (12.55%, Raimondo et al, 2010) and for the Tuscan Archipelago (10%, Lazzaro et al, 2014).…”

“…The American predominance featuring alien flora -invasive and not invasive-of Sardinia and Corsica, is a constant in many Mediterranean areas, both islands -such as the Balearic Islands (Podda et al, 2011(Podda et al, , 2010 (Arianoutsou et al, 2010). Other relatively important contributions to the exotic flora of Sardinia and Corsica, as for the other mentioned territories, come from Asia, from the Mediterranean basin and the African continent; with respect to the invasive flora, it is to be noted that the Mediterranean component is significantly reduced.…”

“…When considering the life forms that characterize both the alien and invasive component of Sardinia and Corsica, the predominance of phanerophytes -mainly introduced for reforestation, forestation and ornamental use-, of therophytesspread as seed contaminants, due to the degradation of habitats and fires-and, to a lesser extent of hemicryptophytes, were also observed in other islands, such as the Balearic (Podda et al, 2010) and the Tuscan Archipelago (Lazzaro et al, 2014) and continental areas, like Spain (Sanz Elorza et al, 2004). The substantial contribution of geophytes is due to their mechanisms of adaptation and resistance to fire, very common in the Mediterranean area.…”

“…Other relatively important contributions to the exotic flora of Sardinia and Corsica, as for the other mentioned territories, come from Asia, from the Mediterranean basin and the African continent; with respect to the invasive flora, it is to be noted that the Mediterranean component is significantly reduced. In light of what emerges from the analysis of introduction pathways in Sardinia and Corsica as well as in other Mediterranean contexts (Lazzaro et al, 2014;Podda et al, 2010;Sanz Elorza et al, 2004), the greater invasiveness that characterizes neophytes has been confirmed, associated to intentional introductions, in particular to the entities cultivated for ornamental purposes.…”

“…The analysis of the habitats where the largest number of alien taxa occur, or where some of these plants show an increased invasiveness indicates, as noted above for other territories (Podda et al, 2010;Sanz Elorza et al, 2004), that one of the basic factors explaining the arrival of non-indigenous entities, of their permanence in the two islands and their possible tendency to invade, is the loss of wilderness, phenomenon usually favoured by human activities and by changes in land use, as revealed in synanthropic and ruderal habitats. In contrast, although aquatic, coastal and riparian habitats host a relatively small number of alien taxa, it is equally true that being these habitats clearly marked by similar ecological conditions regardless of geographical and climatic conditions, these habitats are particularly susceptible to invasions and suffer the presence of some of the most invasive entities of both islands (Blondel and Médail, 2009;Mascia et al, 2009;Nucci et al, 2012;Schnitzler et al, 2007;Zedler and Kercher, 2004).…”