|Pack of dried porcini containing three species |
new to science (Photo: B. Dentinger)
As much as Earth's unexplored wilderness shrinks every day, we are actually discovering more species than ever before. By doing more systematic and thorough surveys, by heading deeper into unknown territory and by using advanced tools like DNA barcoding, we are uncovering new species at a record rate. Last year scientists found some 18 000 new species and that does not include new species of microbial life.
A group rife with such new discoveries is the kingdom of Fungi which might be one of most diverse groups of eukaryotes with estimates ranging from 500,000 to nearly 10 million species, yet they remain vastly underdocumented.
Over the last 40 years the way that we have defined fungi has changed several times. In the early 20th. Century, until around the 1950's, botanists used the term fungi to include all members of the "plant kingdom" that did not have stems, roots, leaves and chlorophyll. In 1952, Constantine Alexopoulos defined fungi, as being "nucleated, achlorophyllous organisms which typically reproduce sexually and asexually, and whose usually filamentous branched somatic structures are surrounded by cell walls". In 1962, when the second edition of Alexopoulos' Introductory Mycology was published he specified that the cell walls of fungi contained cellulose or chitin or both. The definition hasn't changed much despite the inclusion of modern technology.. Currently, most mycologists define fungi as those organisms that are nucleated, achlorophyllous, typically reproduce sexually and asexually by spores, and whose somatic structure is composed of filamentous branched or yeast, which are surrounded by cells walls composed of chitin.
The present rate of description with an average of about 1200 new fungi species annually, is certainly inadequate for the task of describing all species and new discoveries are often the result of unexpected encounters. In a new study by researchers from England's Kew Royal Botanic Gardens, colleagues found three previously unknown species of mushroom in a commercial packet of dried Chinese porcini purchased from a shop in London.
Porcini mushrooms (Boletus section Boletus) are one of the most traded wild edible mushrooms, but although relatively well known, recent research at Kew had already shown that they are more diverse than previously thought. China is a major exporter of porcini, mainly to Europe, but reliable identification of wild collected porcini can be difficult, especially from less well-known regions.
Although it had been shown previously that unknown species were entering the porcini trade, even the Kew mycologists were surprised when they used DNA barcoding to identify 15 mushroom pieces from the commercial packet and found that all belonged to three distinct species, none of which were known to science:
Surprisingly, all three have never been formally described by science and required new scientific names. This demonstrates the ubiquity of unknown fungal diversity even in widely traded commercial food products from one of the most charismatic and least overlooked groups of mushrooms. Our rapid analysis and description makes it possible to reliably identify these species in the food chain, leading to an improved ability to regulate their harvest and trade, and to monitor potential adverse health effects from their consumption.