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Hidden in the tropics: Retiperidiolia gen. nov., a new genus of bird’s nest fungi (Nidulariaceae), and a systematic study of the genus Mycocalia


Nidulariaceae (bird’s nest fungi) are an understudied group of fungi, and species of Mycocalia J.T. Palmer are the least known taxa in the family. Mycocalia was previously shown to be polyphyletic, but no further research has been conducted to revise the taxonomy of the genus. Here we conduct a phylogenetic study of Mycocalia species using five loci (ITS, LSU, SSU, TEF1, and RPB2) and morphologically examined Mycocalia collections available in herbaria. Our results indicate that two tropical Mycocalia species, M. aquaphila and M. reticulata, are distantly related to M. denudata, the type species of this genus. Accordingly, we propose the new genus Retiperidiolia to accommodate this phylogenetically and morphologically unique bird’s nest fungus lineage, with R. reticulata as the type species. Retiperidiolia reticulata was originally described from Sri Lanka by Petch in 1919. Because the type specimen is in poor condition and no molecular data can be obtained, we designated an epitype based on a recent collection from Thailand. Species of Retiperidiolia closely resemble Mycocalia species except that the peridiole cortex in Retiperidiolia species has a reticulated pattern and members of this lineage are thus far known only from tropical or subtropical habitats. In addition to phylogenetic and morphological characterization, we revised the taxonomy and provided a revised key to accepted species of Mycocalia and Retiperidiolia.

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We wish to thank the curators and collection managers of the herbaria C, DAOM, K, MA, and NY for generously sending fungal specimen loans. We thank Dr. Rosanne Healy, Dr. Nicole Reynolds, and Benjamin Lemmond for their assistance in requesting all the loans for this study. We also thank Dr. Komsit Wisitrassameewong and Tuksaporn Thummarukcharoen for their assistance in locating and shipping herbarium specimens from Thailand. We thank Tachit Thummarukcharoen and Tanakorn Apichitnaranon for their assistance with DNA extraction and molecular sequencing in Thailand. Lastly, we thank the editor and anonymous reviewer for providing helpful feedback which significantly improved this manuscript.

Availability of data and materials

The datasets (alignments) generated during and/or analyzed during the current study are available in the Open Science Framework (OSF) repository, accessible via this link:

DNA sequences generated during the current study are deposited in GenBank ( and will be publicly available upon publication but are available from the corresponding author upon request. Voucher specimens are deposited at publicly accessible fungaria and can be obtained via loans. Specimen information and GenBank accession numbers are listed in Supplementary Table 1.


This work was partly supported by the UF Institute for Food and Agricultural Sciences (IFAS) (to M.E.S.), the NIFA-USDA award FLA-PLP-005289 (to MES), and the Royal Thai Ministry of Science and Technology (to N.K.), Society of Systematic Biologists Graduate Student Research Award (to N.K.), BIOTEC Bangkok Herbarium (BBH) and National Biobank of Thailand (NBT) under National Science and Technology Development Agency (NSTDA) (to R.C., T.B., M.B., and S.A.). The field work in Thailand was supported by Biodiversity Training Program (NSTDA).

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All authors contributed to the study conception. Voucher specimens were collected and processed by N.K., R.C., and T.B. M.E.S. provided lab resources, mentorship, and advice regarding study design and analysis. Data collection and phylogenetic analyses were performed by N.K. Microscopic images were captured by N.K., M.P., and S.A. Line drawings were generated by M.P. and S.A. The first draft of manuscript was written by N.K. and M.E.S., and further edited by R.C. and T.B. All authors read and approved the final manuscript.

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Correspondence to Nattapol Kraisitudomsook or Rattaket Choeyklin.

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Section Editor: Zhu-Liang Yang

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This paper is a part of the Topical collection on diversity and phylogeny of wood-decaying Basidiomycota.

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Kraisitudomsook, N., Choeyklin, R., Boonpratuang, T. et al. Hidden in the tropics: Retiperidiolia gen. nov., a new genus of bird’s nest fungi (Nidulariaceae), and a systematic study of the genus Mycocalia. Mycol Progress 21, 56 (2022).

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