Asplenoceterach barrancense, a small treasure

It is a hybrid extremely low. In the Soller Valley of Mallorca Island I know only a single individual in a crack in a limestone in the bed of a stream flowing down from the mountains surrounding the valley. Share the crack with one parent, the Ceterach officinarum ssp. officinarum and a Asplenium trichomanes ssp. quadrivalens. In its allotetraploid genome has 50% of chromosomes of Ceterach officinarum ssp. officinarum, 25% of Asplenium fontanum and 25% of Asplenium petrarchae ssp. bivalens. It is therefore a trihybrid with  chromosomes of three different ferns Aspleniaceae family, an allotetraploid with 144 chromosomes (2n = 144, n = 72).

Asplenoceterach barrancense in early June with the new well-developed fronds.

This hybrid was described to science in 1972 by German botanist Dieter E. Bennett and Wilfried Meyer, who gave the name "barrancense" to have found in the Barranco de Biniaraix in the Serra de Tramuntana, Mallorca Island. 

In this picture the three ferns are sharing the same crack: the Asplenoceterach barrancense, its parent Ceterach officinarum ssp. officinarum and a copy of Asplenium trichomanes ssp. quadrivalens.

Habitat of Asplenoceterach barrancense. At the same rock, in a more shaded area, there is a large population of its parent Asplenium majoricum. The torrent remains dry for most of the year. (Double click on the photo to enlarge) 

The probability of a spontaneous hybridization as it is as low as that for a person to touch the first prize in the Euromillions lottery. To place this wonder of nature was no need to fall into the same crack a spore of Asplenium majoricum and Ceterach officinarum. Should then germinate at the same time and give rise to two gametophytes, which were each a female oosphere and many antherozoids. Subsequently an antherozoid one of the two gametophytes swam in soil moisture with the movement of their flagella to the gametophyte oosphere other, that drew him with irresistible aroma of fitoferomone malic acid and fertilization took place. The fertilized oosphere generated a hybrid embryo, the Asplenoceterach barrancense, which grew very slowly until after 3 or 4 years its fronds lean over the edges of the crack.

Combined photography with the family, both parents and child trihybrid

Frond well developed in December. 

Like their parents, the Asplenoceterach barrancense supports the long months of torrid heat and extreme drought of Majorcan summer entering  in aestival lethargy, aestivation, completely dehydrating its fronds, which are rolled, shrink, take on a grayish-brown and appear dead. With the first autumn rains, at 24h, rehydrated fronds, are green, they expand, as if nothing had happened, so much so that the sporangia of sori just grow up and take advantage of the humidity to disperse the spores. 

Underside of two basal pinnae with sori Asplenoceterach barrancense about to mature and paleae covering the petiole, rachis and the underside of the pinnae, the legacy of his father Ceterach officinarum ssp. officinarum. (Double click on the photo to enlarge) 

Microscopic photograph of the rachis with paleae having an intermediate structure between the trichomes or glandular hairs of Asplenium majoricum and large paleae of Ceterach officinarum.

 
Photomicrograph of the underside of a pinna with sori partly covered by indusium and abundant paleae more narrow and filiform than the Ceterach officinarum. (Double click on the photo to enlarge)

Underside of another Asplenoceterach barrancense pinna of view at 40 magnification. 

Palea of Asplenoceterach barrancense in microns.

Mature Sori very similar to those of its parent Asplenium majoricum. Comparing the size of the frond with thumb that says we get an idea of the tiny size of the fern, which breaks all the schemes of the genetic probability. Its combination chromosome in a similar animal, equivalent to the spontaneous hybridization of a mule (a hybrid between a horse and donkey), which is the Asplenium majoricum, and an African zebra with double chromosome ( impossible between animals, but in plants ), which is the Céterach officinarum ssp. officinarum, autotetraploid of ancestral Asplenium javorkeanum.


Asplenium fontanum--> X <--A.  petrarchae ssp. bivalens            Asplenium javorkeanum

( FF )                              (PP)                                                        ( CC )
                              l                                                                                                                           l
                              l                                                                                                                           l
       ( Hibridación interespecífica )                                                                               ( Apomeiosis )
                                                   l                                                                                                                          l                      
                              l                                                                                                                          l
                                V                                                                                                                        V 
            Asplenium majoricum -------> X <------- Ceterach officinarum ssp. officinarum 
  ( FFPP )                                   l                                ( CCCC )
     l
         l
        ( Hibridación interespecífica ) 
          l
          l
          V
                                                 Asplenoceterach barrancense      .........................
                ( FPCC )

Detail of mature sori indusium lifted revealing the sporangia. (Double click on the photo to enlarge) 

Sori of the parents of Asplenoceterach barrancense.

And to finish the proof of sterility, aborted spores, dead and partially decomposed unfeasible. Under the microscope there are very few spores and the few that seem to be practically empty or broken. Cultivating the spores in a lunch box after three years there was no germination.