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A RARE tree on the brink of extinction has hit upon an odd strategy to
survive: it is the first plant known to produce offspring just from its pollen.
But in a tragic twist, the same trick may eventually lead to its demise.

The Saharan cypress (Cupressus dupreziana) makes its home in the
parched Tassili N鈥橝jjer desert of Algeria. It is one of the most endangered
trees in the world, with only 231 individuals left alive. Such a small
population would normally be forced to inbreed, leading to high rates of genetic
disease.

But when Christian Pichot from the French National Institute for Agronomy
Research in Avignon and his colleagues looked closely at the tree鈥檚 pollen, they
found something strange going on. The pollen was diploid, having two copies of
its genetic material instead of the usual one.

鈥淲e suspected the embryos didn鈥檛 come from the fertilisation of male and
female gametes, but only from the male diploid gamete,鈥� says Pichot.

To test their idea, the researchers took pollen from the trees and crossed it
in the lab with females of a related cypress. They looked at the appearance and
genetic makeup of the offspring. 鈥淎ll of the seedlings were strictly identical
to the father,鈥� says Pichot. The female reproductive organs simply nourish the
growing embryo.

Cloning itself was probably a desperate attempt to avoid the dangers of
inbreeding. But Pichot says the strategy is ultimately doomed to failure. 鈥淚t is
a dead end because there is no genetic mixture. The species will probably
诲颈蝉补辫辫别补谤.鈥�