Monsoon in Goa brings with it bounties of intellectual and scientific interest. This is a story of accidental discovery of a new mushroom species in Goa University campus which we have named Xerula goanensis. A paper is under preparation for publication in scientific journal after some tests are completed. The world authority on species of mushroom under Xerula is Ron Petersen, University of Tennessee Knoxville, USA, who along with co-author K. W. Hughes published a 625 pages monograph- The Xerula / Oudemansiella Complex (Agaricales) in 2010, thus making our task easier. We would solicit his views before publishing the paper but its important to mention about the discovery because the habitats where such novel species are encountered are threatened.
When My Ph.D. research scholar and a national fellow under government of India’s DST-INSPIRE fellowship scheme Rosy D’Souza brought a large specimen of a beautiful mushroom which she found in our campus to the lab, I immediately suspected that it was unusual because it did not match other species of the same genus which were found in Goa earlier or reported from other states in India. Originally these mushrooms were known in taxonomic literature as Oudemansiella. This was changed to the new name Xerula. The species found sporadically in Goa was identified as Oudemansiella radicata. It had a beautiful disc shaped grayish silky cap, perfectly white spokewheel type gills, a straight brownish stipe to support it and a rootlike extension buried in the soil. Once you try to dig in the soil to remove it intact you would encounter a piece of buried wood.
We still don’t know why these species are produced on buried , decomposing wood. In Molem wildlife sanctuary 27 years ago, braving torrential downpour, when I encountered the first such specimen below a Terminalia (Matti) tree, I could not excavate it from the base easily. After a lot of digging, I traced the rootlike extension to a piece of wood from which it had to be detached and brought to the lab for identification. One thing became clear to me while hunting mushrooms during the monsoon for past 30 years- the daytime temperature, rainfall and soil moisture decides the fruiting pattern of the species. For Xerula fruitbodies to appear, a lot of rainfall is required. The moisture needs to seep in the soil and make the buried wood wet. Only then the Xerula colony multiplies underground and then the mushroom fruitbody begins to drill its way to the surface finally emerging as an elegant tall structure.
Xerula species also exhibit a solitary character. Mostly only a single mushroom is seen in a large plot. Rarely two mushrooms would huddle together. But never one can see a group of Xerula. I had taken training under mushroom biologist A.V.Sathe at Agharkar Research Institute, Pune in 1987. Sathe had surveyed coastal Kerala, Karnataka and Goa and reported three species of Xerula- Xerula longipes., X. indica and X. munnarensis. The later two were new species of Xerula. The mushroom found in our campus is fairly large as compared to above three species and other described outside Goa and India. The intriguing character was a forked root like the tongue of snake. This character is not reported in this genus. So Xerula goanensis has given us a considerable food for thought because mushrooms of Xerula genus produce powerful antibiotics and inhibitors of Cholesterol biosynthesis.
This year the peculiar pattern of rainfall has been very beneficial to a diversity of mushroom species. In an area of less than fifty hectares I encountered 120 species of mushrooms in our campus in past four weeks indicating that climate change is actually favouring the mushroom species. But whether climate change would also show us the presence of hitherto unknown species of mushrooms?. Our experience in field shows that even if we hunt for mushrooms in the same area for several years, its only the unusual weather pattern which produces novel species of mushrooms. So the tentative identification of Xerula goanensis as a new mushroom species provides us a practical ecological and biological indicator to link climate change to appearance of novel mushroom species. Taylor from Institute of Arctic biology, Alaska published a very important paper in 2014 commenting on such aspects. He wrote-“ With accelerating extinction and reorganization of biodiversity on the planet, our ignorance of even its approximate magnitude is cause for concern. Fungal biodiversity hotspots are currently unknown, and we cannot predict either patterns of extinction or new epidemics.
A critical need is to carry out comparable, thorough, and rigorous studies in other biomes to quantify patterns of variation in fungus-to plant ratios and to better understand global drivers of fungal distribution and community assembly. Our results suggest that less than two percent of fungal species have been described, implying that the Fungi are equaled only by the Insecta with respect to eukaryote diversity, and that closely related fungi differ in niche axes related to their roles in the environment.”
(Published in my weekly New Frontiers science column in the Sunday Panorama supplement of The Navhind Times on June 28, 2015)