Lichens back in the fungal fold

时间:2019-02-28 08:18:03166网络整理admin

By Stephen Young FUNGI and algae have got together on at least five separate occasions to form the stable relationship that is a lichen, according to evidence from DNA analysis. Andrea Gargas and Paula DePriest of the Smithsonian Institution in Washington DC, Martin Grube of Karl-Franzens University in Graz, Austria, and Anders Tehler of Stockholm University believe such symbiotic associations may have evolved independently on many other occasions. The fungi that take part in these stable coalitions used to be thought of as members of a separate, self-contained group. But over the past two decades mycologists have come to believe that they are closely related to their more conventional cousins. The new research vindicates that approach. “By using molecular characters,” says DePriest, “we can finally begin to understand where the lichen-forming fungi fit in with the other fungi. They are not a different group, they are not separate – they are just normal fungi that do this for a living.” The new findings emerged from a study of 10 lichen-forming fungi and 65 other fungi. In each species the researchers analysed a stretch of DNA that helps build ribosomes, the cell’s protein factories. By studying how this DNA varied between species, they were able to show how the 10 lichen-forming species were related to the others (Science vol 268, p 1492). Most of the fungi that form lichens belong to two main groups the Ascomycota, which includes 98 per cent of the Iichen-forming fungi, and the Basidiomycota. The lichen habit has evolved independently no fewer than three times in the Basidiomycota and at least twice in the Ascomycota, say the researchers. The findings have been welcomed by mycologists such as David Hawksworth of the International Mycological Institute in Egham, Surrey. “The molecular data show what some specialists have thought to be the case, on the basis of other characteristics, for the past twenty years or so – that we do have many evolutionary events of lichenisation and delichenisation taking place,