Sunday, April 1, 2012

Euphorbia margalidiana: it lives alone in an islet

The greater islet of Ses Margalides, located closely together of the coast the northwest of the Island of Ibiza, lodges a unique botanical treasure, the Euphorbia margalidiana, an extraordinary plant that was isolated on the islet after raising the level of the Mediterranean Sea million years ago and evolved undergoing diverse mutations to adapt to an extremely dry rocky habitat, whipped by strong winds, with a very little and salty substrate by the continue splashes of the marine water and an intense insolation without the protection of the minimum shade.

 Euphorbia margalidiana inflorescence at the end of March. I recommend to extend the photos with a double click to appreciate better the details.

Both islets of Ses Margalides. The little vegetation that can be seen on the greater islet is formed almost exclusively by about 200 adult units of Euphorbia margalidiana of until a meter of height. In the smaller islet any unit of this endemism does not live.

Islets of Ses Margalides closely together of the coast of Ibiza.

The arrow indicates the exact situation of Ses Margalides.

The Islets of Ses Margalides are located in the Western Mediterranean. About 6 million years ago, during the Messinian Period, the Mediterranean Basin was dried almost completely and what now they are two Islets surrounded by the water were then two great rocks integrated in the top of a mountain that comprised of the Betic-Rif Massif. After changing the climate and open the Straits of Gibraltar, the Mediterranean Sea filled again of water and what they were mountains became islands and islets, being isolated the ancestor of Euphorbia margalidiana of its congeners of Ibiza, that belonged surely to Euphorbia squamigera species. The isolation in so adverse conditions forcet it to adapt not to be extinguished.

All the photos that I show you belong to units worked in the magnificent Soller Botanical Garden, located in the Island of Majorca, because the access to Islets of Ses Margalides is prohibited by the law. In the image a vigorous unit of about 80 centimeters of height is seen initiating the spring flowering.

The leaves of Euphorbia margalidiana are great of up to 7 x2´5 centimeters, glaucous with a clearly green color slightly bluish, lanceolate, with the pointed apex, of whole margin and without no hairiness, that is to say, glabrous.

In order to adapt to the conditions of extreme drought of the islet the Euphorbia margalidiana underwent diverse mutations transforming its ligneous stem into suculent one accumulating in it the rainwater, since the cactus and the succulent plants do, to be able to support to the length, torrid and parched summer of Ibiza. In the image we see the succulent stem and the detail of the white line of raquis of the leaves. The tiny white small points are grain of pine pollen.

Underside of a leaf of a green color more clearly than the anverse.

The flowering begins at the end of March. The nectar produced by the five nectaries of the flowers likes much to the ants that are its pollenizers in the islet.

 Another pollenizer ant feeding on the rich nectar of a just opened flower.

Euphorbia margalidiana inflorescence. In the image we can see a small insect without wings, that I suspect that it could be a predator of ants.

Another inflorescence.

Image in detail with all the components of one of the five divisions that form the inflorescence. The five nectaries surround five masculine flowers without petals each by them reduced to simple stamen, who surround a unique feminine flower that it open in the end of a very heavy length pedicel and is trained by a trilocular ovary and in the end three feminine styles.

In the end of the feminine flower of the left we can see the three styles partially welded by their base and the warty surface of the trilocular o tricarpelar ovary which at maturity will result in a fruit with three compartments full of ellipsoid, smooth, compressed, dark gray or black seeds.

Euphorbia margalidiana is in serious danger of extinction by the reduced number of unit in the nature and the small area where it grows that it is reduced to the top of the greater islet of eight hectares. In order to avoid its extinction it is cultivated successfully in several botanical gardens as the Soller Botanical Garden and the Mar i Murtra Botanical Garden and conserve seeds in their Genebanks. It is protected by autonomic, national and international laws.

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