Plant invasions on small Mediterranean islands: An overview

Abstract

Biological invasions have become one of the main drivers of habitat degradation and a leading cause of biodiversity loss in island ecosystems worldwide. The spread of invasive species poses a particular environmental threat on the islands of the Mediterranean Basin, which are hotspots of biodiversity and contain rare habitats and endemic species, especially on small islands, which are highly vulnerable to biodiversity loss. \ud Following a recent survey, in this paper we aim to provide an overview of the present-day non-native vascular flora of small Mediterranean islands based on a sample of 37 islands located in the middle of the Mediterranean sea, off the coast of Italy. By comparing the current data with those gathered during a previous survey conducted in the same study area, we also aim to highlight the main changes that have occurred in non-native plant species diversity, establishment and distribution in recent years, and to present a first general overview of the most prominent plant taxa in the island’s introduced flora, focusing on those most responsible for these changes and those that pose the greatest environmental threats. \ud We recorded 203 non-native plant species, 147 of which have established on at least one of the islands investigated. Overall, we detected a sharp increase in the number of species, in their levels of establishment and in the extent of their distribution within the study area in recent years. This may be explained by the intensification of research on plant invasions, as well as to new introduction, escape, establishment and invasion events on the islands in recent decades. The most remarkable plants detected include acacias and succulents, two groups that appear to be emerging very rapidly and to be posing new threats to the conservation of the islands’ natural environment, especially the genus Carpobrotus, whose spread into natural habitats containing rare and endemic taxa is seriously threatening biodiversity on both a local and global scale.\ud On the whole, our results show that the plant invasion phenomenon in the study area has in recent years intensified considerably. As this process seems likely to continue, we should expect more establishment events in the future and the further spread of species that are already present. This is of particular conservation concern on the islands investigated in this survey, which are rich in endemisms but have been facing deep socio-economic and environmental transformations in these last decades as a consequence of the abandonment of traditional management practices and the development of tourism. Our study thus confirms that plant invasions on Mediterranean islands are a serious environmental problem that threatens biodiversity conservation not only in the Mediterranean biogeographic region but also on the global scale, and highlights the need to further increase efforts aimed at preventing, controlling or mitigating the effects of plant invasions in island ecosystems

Here to stay. Recent advances and perspectives about Acacia invasion in Mediterranean areas

“…In Europe and other Mediterranean areas, some uses of acacias as wood and timber production (Griffin et al 2011), the perfume industry (Perriot et al 2010;Kull et al 2011), stabilisation of dunes and avoidance of sand erosion (Marchante et al 2003;Cohen et al 2008;Del Vecchio et al 2013) or to stabilise slopes derived from the railway construction (Kull et al 2007), played a significant role in their introduction. Consequently, a wide range of Mediterranean biomes are currently threatened by acacias, such as riparian habitats, shrublands, fynbos, sclerophyllous forests, mixed forests, grasslands and prairies, coastal areas and sand dunes, riverlands and watercourses, islands, agricultural fields or tree plantations (Le Maitre et al 2000;Marchante et al 2003;Rodríguez-Echeverría et al 2009;Lorenzo et al 2010a, b;Crous et al 2012;Boudiaf et al 2013;Hernández et al 2014;Lazzaro et al 2014;Celesti-Grapow et al 2016). In fact, invasive acacias have been also defined as transformers, those species that "substantially change the character, condition, form or nature of ecosystems, becoming active agents in region-forming processes" (Richardson et al 2000a;Marchante et al 2011a).…”

Evaluating Hypotheses of Plant Species Invasions on Mediterranean Islands: Inverse Patterns between Alien and Endemic Species

“…The Mediterranean islands are considered more vulnerable to invasive alien species introductions than their comparable closest mainland areas due to their proportionally lower native diversity and the presence of unsaturated local communities , and evidence suggests there have been major increases in the number of invasive alien species recently (Celesti-Grapow et al, 2016). Moreover, the historical and modern importance of ports, trade and anthropogenic disturbance, with changes to land use and climate are likely facilitating further the introduction and establishment of alien species (Ross et al, 2008).…”

Alien taxa of the tribe Senecioneae (Asteraceae) in Italy: a nomenclatural synopsis

“…Alien status in Italy: Invasive. Delairea odorata was reported as invasive in Sardinia, where however it occurs in ruderal habitats only, not causing ecological impacts (Bacchetta et al 2009, Camarda et al 2016). In the peninsular Italy, this species is mostly considered as a casual taxon.…”

“…In the peninsular Italy, this species is mostly considered as a casual taxon. Occurrence in Italy (Table 1): Invasive in Sardinia (Bacchetta et al 2009, Camarda et al 2016; naturalized in Tuscany (Frangini & Carta 2010); casual in other regions of peninsular Italy [Liguria, Lazio, Abruzzo, Campania (Stinca et al 2012) and Calabria]. Typification of Delairea odorata: Lemaire ( …”

“…Further recent works (contemporary or later published than Celesti-Grapow et al 2010) were also consulted and cited when necessary (Anzalone et al 2010, Banfi & Galasso 2010, Arrigoni & Viegi 2011, Podda et al 2012, Camarda et al 2016, Celesti-Grapow et al 2016). …”