Invasive alien species in Macaronesia

"[…]. As a consequence of all the geographic conditions and of historical events, the Canaries show the richest biodiversity. As an example, regarding endemic taxa, the Canaries have 524 vascular plants and 2768 arthropods (Martín Esquivel et al. 2005) while the Azores have 72 and 267, respectively (Borges et al. 2005) and the archipelagos of Madeira and Selvagens altogether have 154 and 979 (Borges et al. 2008a) respectively. It is well known that there are several plant genera in the Canaries with high numbers of species (Aeonium, Echium, Argyranthemum, Sonchus, etc.), which probably resulted from adaptive radiation, while in the Azores endemic plant species are found at a rate of one, and more rarely two or three species per genus. An intermediate situation is found in Madeira where genera Argyranthemum (Asteraceae) and Sinapidendron (Brassicaceae) show six endemic taxa (Jardim & Sequeira 2008). There are also other significant differences among the archipelagos. For instance, regarding vertebrate taxa, in the Azores there are no native species of reptiles and there are only two native mammal species, two bats, one of which endemic (Nyctalus azoreum), while there are several species in those groups both in the Canaries and in Madeira, namely the small lizard from Madeira (Teira dugesii, with four subspecies) or the giant lizards from La Gomera (Gallotia bravoana), El Hierro (G. simonyi), Tenerife (G. intermedia) and Gran Canaria (G. stehlini), among others. Thus, although there are similarities among the different regions, important geographic differences dictated that the native flora and fauna would show striking differences among the archipelagos. This is of considerable importance in order to understand what happened in each region, regarding the introduction of alien species. For instance, it is usually accepted that several species of Mediterranean distribution are considered as native in Madeira or in the Canaries, while the same species are considered as alien in the Azores.

Establecimiento de plantas introducidas en la flora vascular silvestre canaria. II (Dicotiledóneas).

Establishment of introduced plants in the Canarian wild vascular flora. II (Dicots)Palabras clave. Corología, novedades, plantas invasoras, Islas Canarias, plantas ornamentales.Keywords. Chorology, new records, invasive plants, Canary Islands, ornamental plants

Establecimiento de plantas introducidas en la flora vascular silvestre canaria. I (Helechos, Gimnospermas y Monocotiledóneas). Establishment of introduced plants in the Canarian wild vascular flora. I (Ferns, Gymnosperms, and Monocots)

Establishment of introduced plants in the Canarian wild vascular flora. I (Ferns, Gymnosperms, and Monocots) Palabras clave. Corología, novedades, plantas invasoras, islas Canarias, plantas ornamentales. Keywords. Chorology, new records, invasive plants, Canary Islands, ornamental plants

A synopsis of feral Agave and Furcraea (Agavaceae, Asparagaceae s. lat.) in the Canary Islands (Spain)

Background – Species of Agave and Furcraea (Agavaceae, Asparagaceae s. lat.) are widely cultivated as ornamentals in Mediterranean climates. An increasing number is escaping and naturalising, also in natural habitats in the Canary Islands (Spain). However, a detailed treatment of variously naturalised and invasive species found in the wild in the Canary Islands is not available and, as a result, species identification is often problematic. Methods – The present study is based on many years of fieldwork on the islands of Fuerteventura, Gran Canaria, Lanzarote and Tenerife. Results – Fourteen species and several additional infraspecific taxa of Agave have been identified. In addition to the widely naturalised and invasive Agave americana, A. fourcroydes and A. sisalana (incl. the not previously reported var. armata), the following species of Agave were observed: A. angustifolia (incl. var. marginata), A. attenuata, A. filifera, A. franzosinii, A. lechuguilla, A. macroacantha, A. murpheyi, A. oteroi, A. salmiana (var. ferox and var. salmiana), A. aff. tequilana and A. vivipara. From the genus Furcraea three species were found: F. foetida, F. hexapetala and F. selloana. Several of these newly detected species of Agave and Furcraea are at least locally naturalised. A key for the identification of the representatives of these genera in the study area is presented and all species are illustrated. Additional nomenclatural, taxonomic and ecological notes are also provided