Missing mushroom genes reported in ScienceDaily 18 July 2012 and PLoS ONE, DOI: 10.1371/journal.pone.0039597. Some mushrooms live in symbiotic relationships with trees, each supplying essential nutrients to the other. Other mushrooms live separately on forest floors amongst the forest litter. Researchers at Harvard University and New York Botanical Gardens have studied the genetics of over 100 species of Amanita mushrooms in order to draw up an evolutionary tree of mushrooms. They found the symbiotic mushrooms lacked two genes for producing cellulases – enzymes that break down cellulose. This means they cannot live independently because they can’t break down the forest litter to obtain food. The research team believe this is evolution by gene loss. They wrote: “Experiments confirm that symbiotic Amanita species have lost the ability to grow on complex organic matter and have therefore lost the capacity to live in forest soils without carbon supplied by a host plant. Irreversible losses of decomposition pathways are likely to play key roles in the evolutionary stability of these ubiquitous mutualisms”.
Anne Pringle, an evolutionary biologist, one of the research team commented: “There had been earlier suggestions that this type of gene loss might be taking place, but our study is the first precise test of that hypothesis. The idea makes sense – if you’re going to actively form a cooperative relationship with a tree, you probably shouldn’t simultaneously be trying to break it apart and eat it. But it’s a very tricky dance to form these kinds of tight, cooperative interactions, and I think this work shows there is a cost associated with that. You have to change, you have to commit, and it can become a sort of gilded cage – these mushrooms are very successful, but they’re stuck where they are”.
Editorial Comment: The scientific observations are that those mushrooms that grow symbiotically with trees do not have cellulose breaking enzymes. At present there is no known evidence they ever had them in order to lose them. The evolutionary tree drawn up by the research team is therefore not evidence. It is an idea imposed on the evidence.
Even if the mushrooms did once have the genes for the cellulose breaking enzymes but lost them, that would be change, but it would not be evolution. Losing genes is the opposite of evolution.
This study is, however, a good reminder of how living things are designed to live together, rather than be in a perpetual “war of nature” as Darwin described it. Mushrooms that grow in association with the trees obviously do not need such enzymes because they are well suited to be part of an ordered and well working system, whilst mushrooms that do have them are just as well suited for living in places where they need the cellulase enzymes, and so they have them. Again, a reminder that there are plenty of theories and opinions that disagree with the Genesis record but the facts never do. (Ref. fungi, symbiosis)
Evidence News 1 August 2012