Sunday, December 26, 2010

Asplenium x tubalense, a cheat hybrid

Thus we might qualify it, because despite its theoretical sterility allotetraploid hybrid status is achieved successfully overcome it and make fun of science, filling children themselves identical, clones, the walls of the terraces of Soller on the Isla de Mallorca. Just so you understand, if we want a faux animal because of its vigor, is like a mule mares, the son of a donkey and a mare, whose mother gives it a large and very strong (the other option is a mule hinny, son of a horse and a female donkey, which is smaller but stronger, as her mother). For comparing the two hybrids, the animal and ferns, according to science both should be completely sterile, but sometimes there are exceptions and either one or the other able to reproduce. A few years ago appeared in newspapers Mallorca news of a mare mule was fertile and had several good healthy foals, although in his case by retrohybridization with a normal horse. In the case of Asplenium X tubalense, the result of a cross between Asplenium azomanes and Asplenium trichomanes ssp. quadrivalens, the mockery of science is a very small percentage of spores completely viable and fertile, while the vast majority of the remaining spores are unviable and aborted, reduced to a shapeless mass, sticky and black, as if they were rotten in the uterus (sporangium) before birth.

Vigorous Asplenium X tubalense with long fronds about 30 cm. that stretch searching for light.
Shows microscopic spores and sporangia of Asplenium X tubalense. Clearly shows the absence of normal spores, only black masses are no definite form, which are only aborted spores, broken and glued together. Some sporangia have been unable to eject the spores inside the bag, being a sticky amajiso and reporting.

However, with patience, sifting through dead spore so, so much as a spore appears completely normal and viable. Through a trap reproductive perhaps apomesiosis (no meiosis by mutation of the gene that encodes) at one of its sporangia, this vigorous ferns spores able to form a viable chromosome combination, whether tetraspores or diplospores, which germinate and by gametophytic apomixis (another mutation that allows growth of a fern from a somatic cell of a gametophyte, bypassing the normal sexual reproduction), get children fill the walls of several terraces of a small area of the Soller Valley. While this may seem like science fiction, the reality is that his father and grandfather, Asplenium azomanes and Asplenium azoricum, were formed by hybridization about 6 million years, were also sterile and allotetraploid hybrids, however, species are now well defined and stable with 100% viable spores. A more recent example, which still produces some aborted spore is the allotetraploid hybrid Asplenium majoricum, which is already a well-defined and stable species and perfectly fertile and successful.

Here you can see a completely normal spore, attached to the mass of dead spores nonviable.

Cool and moist habitat of Asplenium X tubalense with a hundred copies, surrounded by their parents, and Asplenium Asplenium trichomanes azomanes ssp. quadrivalens. This hybrid is very demanding orientation and only grows facing north-northwest. If you look, the substrate on which they grow these ferns is formed by the remains decomposed and accumulated over centuries of mosses, lichens and especially Selaginella denticulata, which being also a fern, moss grows like a sponge and absorbs ambient moisture, promoting the life of ferns patch. (Double click on the picture to enlarge)

In this photo you can see a copy of Asplenium X tubalense with long fronds with the apex elongated and stretched thin looking heliofília its strong light and the top right one parent, the Asplenium azomanes of more fronds short with apex less elongated and more blunt, which apply to the stones in a desperate attempt to escape the light. This simple detail, heliophobia-heliophilia, allows to differentiate them at first. All around him, sharing the same habitat, one can see three ferns:  up several Polypodium cambricum fronds, in the center two copies of Ceterach officinarum ssp. officinarum and growing like moss, Selaginella denticulata. Five fern coexisting in perfect harmony.

Marked differences between Asplenium X tubalense and his parent Asplenium azomanes. However, despite the striking differences in their leaflets and their tips, share and plastic leathery texture of its fronds and a thick spine difficult to fold.

Underside of fronds with several differences that allow for easy identification. Also sori and their arrangement on the underside of the pinnae differentiate them.

Striking difference in the length of the fronds. The child lives with one of the characteristics typical of hybrids, what geneticists call hybrid vigor. This crispness comes in part from the genes of its parent, the Asplenium trichomanes ssp. quadrivalens, under optimal conditions reaches a large size. Remember the simile of the strength of the mules Yeguare sons of a mare, big and strong like her mother. "He shall Asplenium X tubalense a oosphere of Asplenium trichomanes ssp. quadrivalens (female parent = mare), fertilized by a antherozoids of Asplenium azomanes (male parent = donkey)?. Did hence the force is excessive? Does it happen maybe like in mammals, we inherit from our mothers metabolism through mitochondrial chromosome content in the female egg and the sperm lacking?

To finally show you the characteristics of this small fern, endemic to Mallorca, still ignored by Flora Iberica, in this picture you can see the leaflets leathery texture with small atrium at its base oriented towards the apex and the two wings of his rachis that draw a canal, which runs along the frond. These two wings in the face of the rachis are typical for all large family members trichomanes complex.

All descendants of Asplenium anceps have this curious atrium at the base of the leaflets oriented towards the apex with one, two or three sori inside. The remaining sori are located close together along the centerline of the pinna. In this case, the sori are ripe and the white membrane that covered the indusium, has taken off to allow dispersal of spores. Note also the thick spine of a dark maroon almost black and very bright. (Double click on the photo to better appreciate these details.)

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