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Popular Science: A slightly uncovered diversity of microscopic fungi in the Neotropics

There is no doubt that there has not been sufficient exploration of the diversity of organisms in tropical areas. This also applies to microscopic ascomycetous fungi, whose unexplored diversity is always in the focus of mycologists' attention in both temperate and tropical regions. This time Ondřej Koukol from the Department of Botany of the Faculty of Science, Charles University and his colleagues from the Czech Republic and abroad, during three expeditions, focused on the tropical genus Hermatomyces.

Molecular genetics is largely used when studying the diversity and taxonomy of fungi. However, these analyses are not always performed correctly. Without regard to the phenotypic traits observed directly (especially the shape and size of the askospores - sexual spores and conidia - asexual spores) or described in literature, the result is uncritically described new species that were actually discovered earlier.

Three species of Hermatomyces. A, D, G, J. H. reticulatus. B, E, H, K. H. sphaericoides. C, F, I, L. H. sphaericus. Source: Ondřej Koukol

A team of mycologists from the Czech Republic, the USA, Panama and Germany, led by Ondřej Koukol, managed to clarify species boundaries in the species of the tropical genus Hermatomyces. This genus is characterized by the formation of bushy colonies within which two types of multicellular spores are formed. Representatives of the genus Hermatomyces are relatively commonly found in the tropics of the New (America) and the Old (Europe, Africa, Asia) world on the branches of various tree species in the fall. Fresh material originated exclusively from the lowland tropical forests of Panama where it was collected during three expeditions between 2015 and 2017 by Ondřej Koukol and his students. The study of herbarium items borrowed from the herbarium of the National Museum in Prague, New York Botanical Garden (USA) and Royal Botanical Garden in Kew (Great Britain) was also crucial. Although some items were more than 120 years old, the morphological traits remained preserved, and these items could be identified with freshly harvested species. Through a detailed study of the fresh material and herbarium items, it was possible to find the traits that were substantial to defining existing species and describing new ones. In addition to the optical microscope, all species were also observed in a scanning electron microscope, so the resulting publication is supplemented with extensive image material.

Although five new species have been described for science, the total number of known species in this genus has decreased from 17 to 16. For the six species described for science recently, between 2016 and 2017, it has been revealed that they actually represent known species from the past. This study has shown that targeted collection of a particular group of fungi in a certain area may lead to the discovery of species that have been overlooked and that phenotypic traits must always be confronted with the results of molecular genetic analyses. The study of herbarium items played a big role. Although molecular genetic methods are highlighted today, collections stored in herbariums are a very valuable resource, without which it is not possible to reliably determine species boundaries in some groups of (not only) microscopic fungi.

Koukol, O., Delgado, G., Hofmann, T. A., Piepenbring, M. (2018). Panama, a hot spot for Hermatomyces (Hermatomycetaceae, Pleosporales) with five new species, and a critical synopsis of the genus. IMA FUNGUS 9(1): 107–141. doi:10.5598/imafungus.2018.09.01.08.

Radka Zelená

Published: Oct 29, 2018 06:35 PM

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