To Ersymum incanum it does not seduce him that the wind carries his pollen to another plant. Nor that the bees visit her for, with her wings and paws stained with that pollen, transport it and fertilize plants that are not herself. The Ersymum incanum it is more to manage alone and to self-fertilize. In fact, one more between 12% and 15% of all plant species that are self-pollinated, according to the researcher of the University of Granada Mohamed Abdelaziz, that is, that they fertilize themselves. A team of five researchers from the UGR and the CSIC led by Abdelaziz has discovered, however, a self-pollination mechanism that distinguishes it from the rest: The anthers of the Ersymum incamum they rub each other for hours, in a kind of self-massage coordinated to drop the pollen on the stigma and thus achieve the self-pollination of the plant.
Self-pollination, known as selfing syndrome in English and the equivalent of hermaphroditism in the animal kingdom, it is not, given its percentage of occurrence, a major phenomenon, but it is also not unusual in the plant world. In this model of fertilization no help is required beyond the flower itself and the pollen passes from the stamen to the stigma, from the masculine to the feminine part, from the plant without knowing the outside world. The most frequent way to achieve this is to grow the stigma until it reaches the anther, the upper part of the stamen and where the pollen is located. There, pollination occurs by contact. It is also normal for the flower to open and close so that in the movement the pollen falls. But the one described by the Abdelaziz group, and published in The American Naturalist, it is very different. The anthers, above or at the same height as the stigma, do all the work. "For ten hours or more, the anthers produce a continuous movement similar to a massage between them that allows the pollen to pollinate the flower. This species, moreover, has specialized so much in self-fertilization that it does not interest any other type of reproduction ". The researchers have documented in a time lapse in which every second of video is 12 minutes of real life of the plant.
The Ersymum incanum is an herbaceous plant with yellow flowers that is easily found in Spain and North Africa. The researcher says that he had a common name, very, very, until the nineteenth century and was used for a throat treatment. Abandoned use, the vulgar name was abandoned. But its former utility was not the purpose of the study. According to this specialist in genetics, "within this species there are exogamous and inbred plants and we wanted to know the reasons for this and, since they were very efficient reproducing, to explore how their reproductive system had evolved and if there was some mechanism that made this self-pollination. " For this, the group – formed by five specialists in genetics and ecology – planted seeds from the Sierra Nevada and two different areas of the Moroccan Atlas. The sowing was done in a greenhouse to prevent the interaction of wind, insects or any other external conditioner. Not all managed to get ahead but enough to let the video portray their taste for self-massage and the reproductive success that movement implies. "In addition to showing the super specialization in self-fertilization of this species, it reveals that plants are not passive beings or quasi, but are capable of generating movement with specific objectives," Abelaziz explains.
Consequences of inbreeding
As in people, consanguinity has its risks, although survival in the long term minimizes them. According to Abdelaziz, autogamy has for plants "a cost of undoubted biological success. This is what is known as depression due to inbreeding or, in other words, plants become impoverished since, in general, they reduce their variability and lose diversity, becoming plants with little pollen, little flower and little nectar ". Actually, it's a matter of economics. "They do not need pollinators and do not invest in that," concludes Abdelaziz. Time, however, reduces the risks. "There are plants and animals, such as snails, that have managed to remove negative and recessive variants from their gene pool."
The researcher recalls the case of the Egyptian pharaohs who, considering themselves gods, married among relatives. In the medium term, "that would have an obvious cost, but if that holds for many generations, the alleles that remain in time are those that no longer have these recessive and deleterious copies. The same has happened with these plants. They have managed to get rid of that destructive genetic load at the cost of losing also variability and get a poorer species with less ability to evolve and new species appear. This ends in the hypothesis 'of the blind alley of autogamy', which is summarized in that all species that manage to overcome the disadvantage of selfing or autogamy, they become impoverished and do not diversify or end up becoming extinct ".