HUMANKIND has created a new species for the first time. Not by building it from genes, as Craig Venter said he was planning to do last week (New 杏吧原创, 30 November, p 12). And not by millions of years of isolation, as mother nature has tended to do in the past. But instead by a simple lab experiment.
The most remarkable part of the discovery is how easy it is. The method takes just two weeks and the joint American and British team has already created 80 new kinds of yeast 鈥� the single-celled creature best known for converting sugar into alcohol (Science, vol 298, p 1774). 鈥淲e can all do this,鈥� says Dolph Schluter at the University of British Columbia in Vancouver. 鈥淎nybody can create a new yeast species.鈥�
The process is called 鈥渉ybrid speciation鈥�, and it uses two closely related parent species to create a third, unique species. Although other researchers have used a similar method to create plant species in the lab, those plants already existed in nature. This is the first time that a creature new to the planet has been born on a lab bench.
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Also, those previous recreations of existing plant species were achieved using what is called 鈥減olyploid speciation鈥�, in which a new species can鈥檛 mate with its parent species simply because it has a different number of chromosomes. The newly created yeast shows that it is just as easy to produce a species that has the same number of chromosomes as its parents but still can鈥檛 mate with them.
The team, led by University of Houston biologist Michael Travisano, mated two closely related yeasts 鈥� Saccharomyces cerevisiae and S. paradoxus. The offspring of this union are generally infertile, just as when a donkey and horse mate to produce a mule.
There is, however, a way that one per cent of yeast offspring can go on to reproduce. One cell first has to clone itself, a natural part of yeast reproduction, and produce a population of identical cells. One of the cloned cells then has to spontaneously change its gender or 鈥渕ating type鈥�, another trick yeast can pull off. The two then mate. Their offspring constitute a new species because they can mate with each other but have very low fertility with both of the parent species (see Graphic).
The method is so simple that you might expect it to happen in the wild, and it probably does. Many of the yeast species traditionally used to brew beer in Europe seem to be odd genetic mixtures of species. No one knows how they came about, but hybrid speciation might be the answer. A version of the same mechanism could be at work in some plants and animals too. Likely candidates include fish that can change sex, or hermaphrodite snails 鈥� in fact anything that can self-fertilise.
Traditionally, the discoverer of a new species gets to name the creature as a reward. But with 80 novel species on their hands, British team member Rhona Borts from the University of Leicester says that hasn鈥檛 exactly been their top priority. 鈥淲e haven鈥檛 actually thought of that yet,鈥� she says.