19 Novembro 2018. 18:00. Local: Sala de reuniões do DFP. Madison McCuculloch. Estudante de mestrado da University of Kentucky. Humans have a natural tendency to order the world around them because once something has been categorized, it can be further studied and understood. The scientific discipline of biological classification is taxonomy, and the taxonomy of fungi has always been a contentious subject that is often in flux. Fungal taxonomy began as a discipline based on physical characters and ecology for species delineation, but as molecular technology has improved, genetic sequencing has become the new standard for fungal identification and classification. While this advancement has improved fungal taxonomy and phylogenetics and expanded the number of potential species we can detect, the question remains: how much can or should we rely on DNA alone for species identification? At the most recent International Mycological Congress in July 2018, there was a proposal and discussion about making changes to the International Code of Nomenclature for algae, fungi, and plants to allow for the naming of novel fungi identified solely by DNA, which would allow DNA to be the type for a species as opposed to a physical specimen (Hawksworth et al. 2018). If the proposed change were to be approved, potentially thousands of species identified from environmental DNA could be named and placed in the fungal tree of life, which would improve communication and potentially elucidate new phylogenetic relationships (Hongsanan et al. 2018; Zamora et al. 2018). However, there are many pitfalls about which members of the mycology community have raised concern. Without a physical type specimen, researchers cannot go back and verify original material or use the type as a continuous source of information (Hongsanan et al. 2018; Thines et al. 2018; Zamora et al. 2018). Moreover, the DNA sequence or the reference database may not be reliable due to PCR and sequencing errors or incorrect sequence identification (Thines et al. 2018; Nilsson et al. 2006). Additionally, there is still much debate about the specifics of using DNA as type. For example, there is no stipulation for how long the sequence has to be or what region of the genome it is from (Thines et al. 2018; Zamora et al. 2018). Even though the ITS and 28S regions have been identified as useful barcoding loci, decisions like where to set the species thresholds need to be made (Vu et al. 2019). I will argue that DNA as type will play an important role in the advancement of fungal taxonomy, but that it is too soon to make an official change to the nomenclature rules. Before opening the floodgates to thousands of potential newly described species, the details of how DNA sequence data can be incorporated into the already standing taxonomic framework need to be further considered.

References

Buee M, Reich M, Murat C, et al., 2009. 454 Pyrosequencing analyses of forest soils reveal an unexpectedly high fungal diversity. New Phytol 184, 449-56.

Hibbett DS, Taylor JW, 2013. Fungal systematics: is a new age of enlightenment at hand? NatRev Microbiol 11, 129-33.

Hawksworth DL, Hibbett DS, Kirk PM, Lücking R, 2018. (F-005-006) Proposals to permit DNA sequence data to be used as types of names of fungi. IMA Fungus 9, v-vi.

Hongsanan S, Jeewon R, Purahong W, et al., 2018. Can we use environmental DNA as holotypes? Fungal Diversity 92, 1-30.

Korf RP, 2005. Reinventing taxonomy: a curmudgeon’s view of 250 years of fungal taxonomy, the crisis in biodiversity, and the pitfalls of the phylogenetic age. Mycotaxon 93, 407-15.

Nilsson RH, Ryberg M, Kristiansson E, Abarenkov K, Larsson KH, Koljalg U, 2006. Taxonomic reliability of DNA sequences in public sequence databases: a fungal perspective. PLoS One 1, e59.

Seifert KA, Rossman AY, 2010. How to describe a new fungal species. IMA Fungus 1, 109-16.

Thines M, Crous PW, Aime MC, et al., 2018. Ten reasons why a sequence-based nomenclature is not useful for fungi anytime soon. IMA Fungus 9, 177-83.

Vu D, Groenewald M, De Vries M, et al., 2019. Large-scale generation and analysis of filamentous fungal DNA barcodes boosts coverage for kingdom fungi and reveals thresholds for fungal species and higher taxon delimitation. Stud Mycol 92, 135-54.

Zamora JC, Svensson M, Kirschner R, et al., 2018. Considerations and consequences of allowing DNA sequence data as types of fungal taxa. IMA Fungus 9, 167-75.