On the origin (and fate) of plants that never flourish

Plants that reproduce exclusively by self-pollination come from populations with extremely low diversity to start. Kobe University Research not only adds a facet to possible evolutionary strategies, but also lends weight to Darwin’s suspicion that this strategy could be a path to extinction.

Charles Darwin once noted: “It is hardly an exaggeration to say that nature tells us, in the most categorical way, that it hates perpetual self-fertilization.” And yet, the botanist of the University of Kobe, Suetsugu Kenji, knows some islands in Japan where the orchids reproduce without ever opening their flowers.

He says: “I have long been captivated by Darwin’s skepticism about plants that count entirely on self-pollination. When I found these orchids not unleashed, I felt that it was a perfect chance to directly review this problem. The apparent distrust to a little evolutionary sense.

On the northern islands of Ryukyu of Kuroshima, Takeshima and Yakushima exist the only wild populations of known plants to reproduce only by self-pollen.

“Our group has spent more than ten years working with lovers of local plants, monitoring more than a hundred individual plants on several islands, so we can say with certainty that these orchids never open their flowers in their natural habitats,” said Suetsugu.

He and his team have decided to submit these populations to a genetic analysis which can detect the tiny differences even between closely linked individuals, which allowed them to follow the flow of genes and kinship.

In the newspaper Acts of the Royal Society BThe team led by the University of Kobe now reports that extreme genetic uniformity between the plants of each species proves that they are really purely self-popular.

In addition, they also found that the two species each came from species pollinated by insects which already have a very low degree of genetic variation in this geographic region. The variation is so weak, in fact, that even if pollen could be transported from one plant to another, it is almost identical to self-pollen.

This is only aggravated by another observation that SUETSUGU made: the pollinating parents crossed on these islands are based on fruit flies with a limited flight capacity. The animals thus pollinate only, if they pollinate plants at all, flowers of the same plant or those that live very close, further reducing the benefit of the pollination of insects.

Suetsugu explains: “Darwin’s Declaration was motivated by the idea that a purely self-popular line line would accumulate harmful mutations and end up facing an evolutionary dead end. However, our results show that for relative species with open flowers, real genetic payment for fruit procreation can be marginal, giving the self-polished orchids, which succeed more to produce. An evolutionary advantage. “

It turns out that Darwin’s skepticism might not have been unfounded. Another result of the study of the University of Kobe is that even with conservative estimates, these self-pollination species have at most 2,000 years. Since there are no other known examples of purely auto-pollinal plants in nature, these species could be ephemeral.

“The fact that these orchids really never outclass the crossing raises intriguing questions about their long -term viability, in particular under pressures such as fragmentation of habitat and climate change,” explains Suetsugu.

He is nevertheless proud of the conclusions of his team, claiming: “Each new data point, each newly described species, approaches me more and more to grasp the whole spectrum of evolutionary possibilities.”