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Fern evolution: Time and chance | The Economist

Fern evolution Time and chance The Economist

What they found shocked them. Before they conducted their search, the only known non-fern neochrome was in a small group of algae. That appeared to be a coincidence; a case of convergent evolution. But their investigations revealed that in addition to these algae a group of primitive plants called hornworts, which are related to mosses but not closely related to ferns, have a neochrome too. This might have been convergent evolution, as well, of course. But closer analysis showed it was not. Instead, the evolutionary tree of fern neochrome fits neatly inside the evolutionary tree of hornwort neochrome. The original gene for fern neochrome—the gene that, in all probability, saved ferns from obscurity—formed in a Mesozoic hornwort and then somehow passed to a Mesozoic fern.

In essence, this is the same process of gene transfer from one species to another that is used artificially to make genetically modified crops. Such a transfer might have happened naturally by a virus picking up the relevant gene and carrying it across the species boundary. Or it might have occurred in the rough-and-tumble of everyday life as a tiny fern grew up abutting a hornwort. The details will probably never be known. But that chance event, which happened, Mr Li’s calculations suggest, about 180m years ago, probably explains why ferns are still around and thriving.


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