Orchid and sitsa

2015/02/12 Etxebeste Aduriz, Egoitz - Elhuyar Zientzia Iturria: Elhuyar aldizkaria

• Biologia
• Historia
• Eboluzioa

Darwin was fascinated with her. He was sent by the prestigious gardener James Bateman in January 1862, along with other orchestras brought from Madagascar. Write to Joseph Hooker: “I just picked up, in a box sent by Mr. Bateman, the surprising Angraecum sesquipedero, whose nectario has a long foot. The ray, what insect will blow that!”

Darwin was investigating the insect pollination of orchids and would write in his book on this subject (On the Various Contrivances by which British and Foreign Orfertilchids are Ised by Insects) that same year: “I am afraid to get tired, but I have to say a few words about Angraecum sesquipedale, whose six-pointed flowers, as if they were stars of white wax, have awakened the fascination of travelers in Madagascar. It has a green nectarian in the form of a latigo of extreme length hanging under the label. In several flowers sent by Mr. Bateman saw that the nectarian was eleven and a half inches long [29.2 cm] and that only the inch below and half [3.8 cm] was filled with very sweet nectars. You can ask what can an exaggerated nectarian serve? We could conclude, I think, that the pollination of this plant depends on this length and nectar that is only in the narrow background.”

Darwin knew that this type of orchids were pollinated by polyneites, and he saw clear that the nectar that was at the bottom of this long nectarian of almost 30 centimeters was a bait for a pollinate. He carried out tests imitating the way to leftover the nectar of the chickens. He put in the nectarian a thin tube, as the glue would with his proboszide, and observed that at the base of the tube the pollen was stuck. If the tube returned to the nectarian, that pollen reached the stigma.

“However, although it is still in the book, it is surprising that some insect can reach that nectar: our English sphinxes have probiotions as long as the body, but it must be in Madagascar those who have a proboscide capable of stretching the moths between ten and eleven inches!”

Darwin proposed that as the chickens became bigger by natural selection (which would make them some advantage), or only as they were lengthened the proviscencia (to blind the nectar of Angraecum and other tubular flowers), the specimens of A. sesquipedale with a longer nectarian would force them to enter in the background In this way, the flowers with a longer necpollinate would have a longer necpollination. Thus, “there seems to have been a stretch race, between the Angraecum nectarium and the tester of a rocket,” Darwin wrote. In addition, they could have such a dependency that “if those great seats disappeared in Madagascar, Angraecum would probably also disappear”.

The book on the pollination of Darwin's orchids was a success. If the idea of evolution was still new, that of coevolution, let's not say. But that story of Madagascar's orchid and pasture also provoked a debate. On the one hand, the sits were unknown and, on the other, there were those who used it as proof of divine creation. In the opinion of Duke of Argyll, George Campbell, for example, it was clear that the orchid and that kind of sits could only be created by God.

Alfred Russel Wallace wrote in 1867 the article “Creation by Law” against the duke and in defense of Darwin’s ideas. He firmly argued how one could reach those incredible lengths through natural selection.

Like Darwin, Wallace was convinced that the rest existed: “I have to say that many of the cocks found in the tropics have almost as long tests as the nectarian of Angraecum sesquipedale. I have measured the prosaic of a number of the South American Macrosila cluentius in the British Museum and have seen that it is nine inches and a quarter of [23,5 cm]. A tropical African (Macrosila morganii) has seven and a half inches [19 cm]. A species with two or three inches of proboscide length could reach the highest flower nectar of the sesquipedale Angraecum... It can be safely predicted that this species of Madagascar exists; and naturalists who visit the island should look for it, with the same confidence that astronomers sought the planet Neptune, and they will be as successful as they!”

In 1873, German botanist Herman Muller, Darwin's defender, published that his brother Fritz had caught a sit in Brazil with almost ten inches (25 cm). And if it existed in Brazil, why not in Madagascar?

Twenty years after Darwin's death in 1903, he was discovered by Lionel Walter Rothchild and Karl Jordan. As expected it was large, with wings open 15 cm and its probósside about 30 cm. Wallace studied Xantophan morganii (then Macrosila morganii) as a subspecies of Xantophan morganii praedicta.

However, this sits was still to prove whether it really sucked the orchid nectar A. sesquipedale. More than one tried to see him. Throughout the twentieth century, we would have to wait for the end of the century. Until 1997. T. T. Lutz The German researcher Wasserthal also failed to see visitors of these flowers, until he finally introduced orchids and sitsas into a salt tent. And then yes, Darwin managed to predict 135 years before and see what many imagined and dreamed after.

But it seems that the stories of Madagascar's orchids and chickens have not finished. In 1965, Jean M. Bosser found an orchid with an even longer nectarian: Angraecum eburneum longicalcar. The nectarian has a length of 40 centimeters and the pollinator is not yet known...

Eskerrik asko to Kepa Altonaga for explaining this special story for Darwin's day. Darwin Day is celebrated on February 12, when he was born in 1809.

Bibliography: Bibliography:

Beccaloni, G.: “Darwin and Wallace Predictions Come True”. The Alfred Russel Wallace Website (2010)

Darwin, C. A: Darwin to Hooker, 25 Jan 1862. Darwin Correspondence Project.

Darwin, C. R. R. “On the various contrivances by which British and foreign orchids are fertilised by insects, and on the good effects of intercrossing”. London: London: John Murray (1862)

Hone, D.: “Moth tongues, orchids and Darwin -- the predictive power of evolution”. The Guardian (2013)

Kritsky, G.: “Darwin’s Madagascan Hawk Moth Prediction”. American Entomologist (1991)

Vázquez, D.: “Charles Darwin, the evolution and the mystery of the moth language”. Ecology Explained (2009)

Wallace, A. W: W: “Creation by Law”. Quarterly Journal of Science (1867)

 

"This entry participates in the 3rd festival #CultureCientífico"