The Valencian Community (Eastern Spain) holds 3 small archipelagos, formed by inlets and very small islands,
but enclosing a remarkable group of rare, endemic or endangered plant species. Two of them are located in the
province of Alicante, by the Southern side of the region, being formed by islands placed near to the coast,
so sharing a common vegetattion but acting as refugee for some endangered taxa; it deals with the
so-called ‘Archipelago fo Tabarca’, and ‘Islands of NE Alicante’; these sites hold populations of several
species protected by the Directive of Habitats, such as Diplotaxis erucoides or Silene hifacensis
-a species closely related to S. hicesiae.
However, the most important site for plant conservation is the Archipelago of Columbretes, formed by a spreaded group of small volcanic islands placed more than 30 marine miles from the coast of Castellon (N of the Valencian Community). It deals with a true laboratory for the biological evolution, holding more than 20 endemic species of animals and plants, on their 14 hectares, distributed into 4 main islands (Grossa, Ferrera, Foradada and Carallot). This islands receive a very low rainfall amount (a bit more than 200 mm/year) so their potential vegetation is close to the Chamaeropo humilis-Rhamnetum lycioidis subass. pistacietosum lentisci, enriched with species fitting semiarid climates such as Withania frutescens or Lycium intricatum. There is an exclusive endemic plant (Lobularia maritima subsp. columbretensis), and the islands also conserve a big part of the world population of the Iberian-Balearic endemic Medicago citrina, and representatives of several North-African plants rare to Spain such as Lavatera mauritanica, Fumaria munbyi, etc.
From 1987, a large group of combined actions have been developed in Columbretes Islands to conserve their rare or interesting species, including the following as more remarkable facts: -Complete eradication of rabbits
-Partial eradication of Opuntia maxima, only maintaining tree specimens in order to food migrating birds and to ensure the larval period of pollinators for Medicago citrina, that use to live into the nopal stems.
-Progressive regeneration on vegetation, planting in each successional step the species to built the inmediately following one, and combinating both seed dispersal and artificial plantations. Species used for the lower steps have been, between others, Elymus farctus, Lobularia maritima columbretensis, Lavatera arborea, L. mauritanica, Beta patellaris, etc. For the upper, the plants where before multiplied by means of vegetative procedures in order to obtain enough plants to generate new seeds, due to the low proportion of remainders from the originary populations of Lycium intricatum, Withania frutescens, Atriplex halimus, etc. Medicago citrina has been mainly planted after plantlets, obtained into the same island.
-Production and plantation of Crithmum maritimum to food several species of endemic insects living on, exclusive to this archipelago.
-Control of attacks of external agents, mainly focused on the invasion of Icerya purchasii, controled by its natural predator Rhodolia cardinalis. I. purchasii destroyed by 1998 most part of the native population of M. citrina.