The phylogenetic origin of the lineage was placed to various parts of Basidiomycota, but according to the analysis of a larger dataset it is a sister group of Agaricomycotina.

The seven described species (W. sebi, W. ichthyophaga, W. muriae, W. mellicola, W. canadensis, W. tropicalis, and W. hederae) are distinguished by conidial size, xerotolerance, halotolerance, chaotolerance, growth temperature regimes, extracellular enzyme activity profiles, and secondary metabolite patterns.

[1][5] They are typically isolated from low-moisture foods (such as cakes, bread, sugar, peanuts, dried fish), indoor air dust, salterns and soil.

[7] However, species from the genus Wallemia are an exception to both of these rules: all species can tolerate high concentrations of sugars and salts (W. ichthyophaga grows even in media saturated with sodium chloride), while W. muriae and W. ichthyophaga cannot be cultivated unless the water activity of the medium is lowered.

[9] Cell wall and morphological changes of Wallemia species are thought to play a major role in adaptation to low water activity.