Revision of sequenced fungarium specimens of Lactifluus: morphology, analysis of amplicon sequence data, and linkage to ecology
Background
It has been estimated that nearly 75% of the earth’s biodiversity is already collected and present in biological collections around the world. These include zoological collections, herbaria, and fungaria. With respect to the kingdom of Fungi, researchers have described approximately 148,000 species of fungi since the start of modern mycology in 1737. However, this only represents about 2.5–6.7% of the estimated diversity in the kingdom. At least part of this dazzling undescribed fungal diversity is likely already present in our fungaria.
DNA barcoding is a modern tool to detect species diversity—and thus to discover undescribed species—faster and more accurately. Researchers identified the internal transcribed spacer (ITS) region of the ribosomal DNA as the universal barcode of fungi. For the majority of fungi, the interspecific variation within ITS exceeds the intraspecific variation. Other secondary barcode regions, such as the second largest subunit of RNA polymerase II gene (RPB2), have been developed for certain groups of fungi for which ITS is difficult to amplify. Such secondary barcodes may be equally good or better in delimiting species compared to ITS.
Problems
Lactifluus is a genus of milkcaps. Approximately 25% of the known milkcaps, about 150 species, belong to this genus. Lactifluus is most diversified in the tropics, especially in Africa and Asia. Members of Russulaceae, Russulales, species of Lactifluus form ectomycorrhizal associations with host plants in the following families: Dipterocarpaceae, Fabaceae, Fagaceae, Myrtaceae, and Phyllanthaceae. A previous study sequenced Lactifluus specimens from the Herbarium Universitatis Gandavensis. This work resulted in good-quality ITS and RPB2 sequences for some 60 specimens. Analysis of these sequences seems to suggest that at least some of the herbarium specimens may be inaccurately identified—potentially harboring undescribed species.
Goals
The goal of this project is to revise species names of the sequenced herbarium collections of Lactifluus. Sequences will be added to a curated dataset of Lactifluus to help with identification. The morphology of herbarium specimens will also be studied using stereoscope and light microscope. Material not matching existing species will be formally described following best practices in the field. Finally, there will be the option the link specimens with miombo woodland soil sequences—to further our understanding of the ecology and host associations of these understudied fungi.
References
De Crop E. 2016. Global phylogeny and evolutionary history of the genus Lactifluus. PhD dissertation, Ghent University. [pdf]
De Crop E, Delgat L, Nuytinck J, Halling RE, Verbeken A. 2021. A short story of nearly everything in Lactifluus (Russulaceae). Fungal Systematics and Evolution 7: 133-164. https://doi.org/10.3114/fuse.2021.07.07
De Lange R, De Crop E, Delgat L, Tibuhwa D, Baribwegure D, Verbeken A. 2018. Lactifluus kigomaensis and L. subkigomaensis: two look-alikes in Tanzania. Mycoscience 59: 371-378. https://doi.org/10.1016/j.myc.2018.02.004 [pdf]
Delgat L, Dierickx G, De Wilde S, Angelini C, De Crop E, De Lange R, Halling R, Manz C, Nuytinck J, Verbeken A. 2019. Looks can be deceiving: the deceptive milkcaps (Lactifluus, Russulaceae) exhibit low morphological variance but harbour high genetic diversity. IMA Fungus 10: 14. https://doi.org/10.1186/s43008-019-0017-3
Nuytinck J, De Crop E, Delgat L, Bafort Q, Ferreiro MR, Verbeken A, Wang XH. 2020. Recent insights in the phylogeny, species diversity, and culinary uses of milkcap genera Lactarius and Lactifluus. pp. 273-286. In: Pérez-Moreno J, Guerin-Laguette A, Arzú RF, Yu FG (eds.) Mushrooms, Humans and Nature in a Changing World. Springer Nature Switzerland AG, Cham. https://doi.org/10.1007/978-3-030-37378-8_9 [pdf]
