Predicting global numbers of teleomorphic ascomycetes

Indunil C Senanayake,Eric H C Mckenzie,Saowaluck Tibpromma,Lakmali S Dissanayake,Rungtiwa Phookamsak,Mei-Mei Xiang,Nuwan D Kularathnage,Subodini N Wijesinghe,Dhanushka N Wanasinghe,Achala R Rathnayaka,Kevin D Hyde,Ning Xie,Dhandevi Pem,Hao-Xing Zhang,Deecksha Gomdola,Dulanjalee Harishchandra,Anusha H Ekanayaka

doi:10.1007/s13225-022-00498-w

Abstract

Sexual reproduction is the basic way to form high genetic diversity and it is beneficial in evolution and speciation of fungi. The global diversity of teleomorphic species in Ascomycota has not been estimated. This paper estimates the species number for sexual ascomycetes based on five different estimation approaches, viz. by numbers of described fungi, by fungus:substrate ratio, by ecological distribution, by meta-DNA barcoding or culture-independent studies and by previous estimates of species in Ascomycota. The assumptions were made with the currently most accepted, “2.2–3.8 million” species estimate and results of previous studies concluding that 90% of the described ascomycetes reproduce sexually. The Catalogue of Life, Species Fungorum and published research were used for data procurement. The average value of teleomorphic species in Ascomycota from all methods is 1.86 million, ranging from 1.37 to 2.56 million. However, only around 83,000 teleomorphic species have been described in Ascomycota and deposited in data repositories. The ratio between described teleomorphic ascomycetes to predicted teleomorphic ascomycetes is 1:22. Therefore, where are the undiscovered teleomorphic ascomycetes? The undescribed species are no doubt to be found in biodiversity hot spots, poorly-studied areas and species complexes. Other poorly studied niches include extremophiles, lichenicolous fungi, human pathogens, marine fungi, and fungicolous fungi. Undescribed species are present in unexamined collections in specimen repositories or incompletely described earlier species. Nomenclatural issues, such as the use of separate names for teleomorph and anamorphs, synonyms, conspecific names, illegitimate and invalid names also affect the number of described species. Interspecies introgression results in new species, while species numbers are reduced by extinctions.

Highlights

Ascomycota Caval-Sm. is the largest fungal phylum comprising around 93,000 extant species and are generally known as “sac fungi” (Bennett and Turgeon 2017; Clark et al 2018; Catalog of Life 2021)
Assessment of the actual number of teleomorphic species in Ascomycota and their diversity is important for systematics, resource utilization, industrial production and environmental management (Maharachchikumbura et al 2021)
Species estimations were based on the numbers of fungi recorded on particular plants and insects

Summary

Introduction

Ascomycota Caval-Sm. is the largest fungal phylum comprising around 93,000 extant species and are generally known as “sac fungi” (Bennett and Turgeon 2017; Clark et al 2018; Catalog of Life 2021). Parasexual reproduction results in recombination of genes from different individuals but does not involve meiosis and formation of a zygote by fertilization as in sexual reproduction Parasexuality generates both genotypic and phenotypic diversity in species (Hirakawa et al 2017). There should be 1.25–2.17 million teleomorphic ascomycetes based on described number of species considering the 2.2–3.8 million species estimate. Estimated number of teleomorphic ascomycetes based on fungus:substrate or host ratio. The estimates based on studies of fungus: plant/ insect/lichen/plant OTUs in soil ratios in a site, obtained by field survey and molecular approaches, have generated lower ranges from 0.42 to 3.5 million to (O’Brien et al 2005; Tedersoo et al 2014) an upper range from 0.6 to 5.1 million (O’Brien et al 2005; Piepenbring et al 2012) (Table 1).

Method

Findings

Discussion and conclusion