Tuesday, May 1, 2012

Helicodiceros muscivorus, the trickster of the flies

The plant Helicodiceros muscivorus is a champion of survival. Over millions of years suffered adaptive mutations that were transforming its appearance to perfection today. It belongs to the Araceae family. Get the names of Dracunculus muscivorus and Arum muscivorum. It is a relic of Miocene that currently populate the rocky shores of islands and islets that about 6 million years ago formed the Tyrrhenian region: the Balearic Islands, Corsica and Sardinia, always near the colonies of gulls.

Helicodiceros muscivorus in full bloom in late April, photographed in the Cap de Formentor of Mallorca Island. I recommend enlarge photos with a double click to see details better.

Helicodiceros muscivorus young exemplary with its typical fleshy leaves bearing a winged petiole and a blade with a long anterior lobe and two posterior lobes. The plant comes from a globose tuber up to 14 centimeters long and 6.5 cm wide, deeply buried in the crevices of limestone coasts. In addition to producing seeds, is repeated by generating small tubercles around the main tuber.

The inflorescence is based on a long peduncle partially buried up to 16 centimeters. The spathe for its outer face has a nice green with spots that resemble the skin of a snake and on its inner side a striking purple pale imitation meat with plenty of purple hair. The bottom of the spathe is rolled into a tube and housing the male and female flowers placed in the bottom of the spadix. It measures between 13 and 40 inches long. Its distal end extends outside the tube and is covered with long dark purple hair.

Helicodiceros muscivorus flower, which is actually an inflorescence with numerous male and female flowers inside the spathe tube deceives the flies by sight and smell. The flesh-colored hairy surface of the spathe mimics a decomposing carcass and the tip of the spadix resembles the bushy tail of a rat with very dark purple hairs arranged in brush. The flower emits an intense stench of rotting flesh that attracts carrion flies the few who survive on rocky shores feeding on the corpses of seagulls, rats and feral goats.

Carrion fly on the spadix. The inflorescence lasts a day and has a female and a male phase well separated to avoid self-pollination.

Same fly before testing the waters. Flies are attracted by the smell of rotting flesh of Helicodiceros muscivorus belong to the genera Calliphora and Lucilia. The photo belongs to the species Calliphora sp. Robineau-Desvoidy, 1830.

Pollination by flies is very typical plants of the Araceae family. The spadix and spathe of all have a very similar structure and all emit a strong odor of carrion. When a fly sees the stench in the air, goes flying and lands on the spathe or spadix. Try sucking the juices of false carrion, but finds nothing. Then note that the bottom of the tube of spathe up a stink even more intense and believes that if there will find something to eat. The spathe is covered with hair arranged in descending which facilitate the descent to the bottom of the tube where the female flowers are receptive. Once inside it realizes the deception and want out, but the hair and other hair down even more called pistilodes radially arranged to form a barrier between male and female flowers, which block it. Other flies have fallen into the trap and one of them has either previously been deceived by another flower and pollen leads attached to its body. In their desperation to get going again and again over the female flowers and pollination. When Helicodiceros muscivorus find that its female flowers have been fertilized, mature faster its male flowers that are covered with pollen. At the same time dehydrates the hair falling and hair do not do radial barrier and flies can leave, but in doing so pass over the male flowers and carried with them the pollen is very sticky. Once out and desperately hungry are attracted to the inflorescences of cheating by other Helicodiceros muscivorus and starts the process of pollination.

Striking spadix hairy perfectly mimics the tail of a rat. The flesh-colored surface of the spathe is also covered with hair. These details tell us clearly what were the stars of this smart evolutionary process: the rats that live in the coastal rocks of the islands, the flies that feed on their bodies and Helicodiceros muscivorus which suited the only pollinators that live rocky shores, because as I found while doing these photos, the only insects I saw were the flies attracted by the flowers of this Araceae. It is evident that these insects can not survive only coastlines with little rat bodies that may be so poor in this habitat. Surely their main food source are the bodies of gulls and other seabirds and their chicks, eggs and their droppings abandoned because it matches the flowering of Helicodiceros muscivorus with the breeding season of these birds. Logically also conceivable that the same rats feed on the carcasses of gulls, chicks and eggs. It all seems a perfect mechanism, cleverly coordinated by nature to facilitate the survival not only of the plant, but also their pollinating flies and rats, omnivorous par excellence, who clean the coastal rocks addled bodies and eggs of gulls, with so that the latter also benefit by having their habitat clean. Perhaps the experimental multiple mutations suffered this plant for millions of years looking for the most efficient of its inflorescence dismissed the transformation into something like a seagull and it was easier and practical look like the body of a rat. It is also possible that in the late Miocene, about 6 million years, when this plant was in evolving and peopled the whole Tyrrhenian region, there is a rodent in the wild now extinct, perhaps a shrew, which the plant tried to look with great success.

Detail of the hairs of the spadix and spathe surface.

Flowering lasts about 24 hours. The next day the spathe folds the edges of the spadix and its tip curving downward. Inside the tube begins the maturation of the ovaries of newly fertilized female flowers that give rise to orange fleshy fruits. 

Helicodiceros muscivorus fruits, still immature. Photography given by my friendly Rafel Cladera and Mª Angeles, great lovers of the life and the nature.

In the Balearic Islands, these fruits are a favored food of the lizard Podarcis lilfordi, sargantana called, that after digesting the pulp defecate the seeds scarified for its gastric juices, which germinate easily paid by the nitrogen of the feces. This detail has been proven by experts from the botanical gardens trying to germinate seeds in pots, as it was shown that those who have previously passed through the digestive tract of sargantanas have a germination rate close to 100%, while if sown directly without taking away the fruits pulp do not germinate or at a very low percentage. Removing the pulp and seeds subjected to chemical scarification with a very dilute acid solution, the success rate is even higher, but never reaches 100% germination of seeds eaten by Balearic lizards. Hence, it is preferable to seek patiently on rocks fresh feces of these little reptiles in the weeks that feed on the fruit. The seeds thus collected should be planted without cleaning the remains of excrement.

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