Fungi of the genus Podaxis are found in dry grasslands and deserts throughout the tropics and subtropics. They are highly modified Puffball Fungi noted for their relationship with grass-cutting Termites, living on the dung of Termites in grass storage areas within the mounds and extruding large fruiting bodies from the surface of the mounds. It is unclear if or how this benefits the Termites, but the tolerance shown by the termites towards the Fungi is remarkable, as they will not otherwise tolerate Fungi or Plants growing on the surface of their mounds. Whatever the relationship between the Fungi and the Termites, neither group appears to be dependent on the other; the Fungi are not found on all Termite mounds, and are found growing away from mounds, particularly in arid regions where Termites are rare. The first of these Fungi was described by Linnaeus in 1781, based upon a sample from India, and he later described two further species from Western Cape in South Africa and Senegal. However the taxonomy of the group is controversial, as putative species can be hard to differentiate by physical examination, with some experts arguing as early as the 1930s that the Fungi might possibly be better referred to as a single widespread species, while others have continued to describe new species, with 44 species described to date from Africa alone.
In a paper published in the journal Fungal Biology on 7 June 2016, Benjamin Conlon of the Centre for Social Evolution at the University of Copenhagen and Molecular Ecology at the Martin-Luther-University Halle-Wittenberg, Wilhelm de Beer of the Department of Microbiology at the University of Pretoria, Henrik de Fine Licht of the Section for Organismal Biology at the University of Copenhagen, Duur Aanen of the Laboratory of Genetics at Wageningen University and Michael Poulsen, also of the Centre for Social Evolution at the University of Copenhagen, describe the results of a study of Podaxis Fungi in Southern Africa, which attempts to use genetic analysis to determine relationships within the group.
Mature Podaxis fruiting bodies in South Africa in the southern Free Stat Province. Conlon et al. (2016).
Conlon et al. took samples from 32 Podaxis specimens from museums, representing all none provinces of South Africa, as well as specimens from Namibia. Genetic sequences obtained from these were then compared to previously described genetic sequences from Podaxis specimens from other parts of the world.
Immature Podaxis fruiting bodies growing on a termite mound in the central Free State Province, South Africa. Conlon et al. (2016).
The southern African Podaxis specimens were found to belong to four distinct clades (a clade is a group of organisms with a shared common ancestor; all
members of the clade must descend from that ancestor and everything shown to be
descended from that ancestor must be included in the clade), identified as Clades A-D. The data from this study also enabled the identification of a fifth clade, Clade E, comprising specimens from southwest North America (California, Arizona and Mexico), which had not been possible from the low number of Podaxis genetic sequences previously available.
One of the Southern African clades (Clade C) was found to form no association with Termites. This clade was found entirely in the Namib desert of Northern Cape Province and Namibia. A single previously described sequence was also placed with Clade C, a desert growing specimen from Ethiopia. Clade C was also found to be most closely related to Clade E, which grows in the deserts of the southwestern US and Mexico, and which also does not form associations with Termites. This suggests that the genus may have previously been exclusively a Termite-mound dweller, with one lineage within the genus secondarily adapting to free-living in arid environments.
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of biological material, but this also makes them spoiling agents capable
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