This fungus was first described from China (Tibet). It has been confused with Favolus pseudobetulinus in Japan, but revealed to be distinct by detailed morphological and phylogengetic studies.

Polyporus subvarius was described from China (Tibet), and later reported from a mountainous area in Hokkaido, Japan. Hitherto only known from one locality in China, and 3 localities (around Mt. Taisetsu) in Japan. This species has high host specificity, and all known collections were made on Salix spp. Salix spp. are intolerant, and can be declined by natural succession. Known localities are situated in boreal mountainous areas, and can be influenced by the global warming.

Hitherto known form one area in China (Tibet), and 3 localities around Mt. Daisetsu, Japan.

Only a single specimen is known from the type locality. 3 localities are known from Japan, only by a single specimen for each locality.

On living (or dead?) trees of Salix spp. in boreal subalpine areas. White rot fungi.

This fungus is specific to Salix sp. in limited areas of East Asian subalpine forest. Decline of the host trees should be a threat for this fungus. Known collection sites in Japan are now reserved.  Salix species are intolerant, and can be decreased by the natural succession. Known localities are situated in boreal mountainous areas, and can be influenced by the global warming.

Conservation of the host trees in the distribution sites is desirable.

This species is confused with Favolus pseudobetulinus, sharing similar ecology and morphology in East Asia. Detailed distribution should be studied for both of the species.

Dai, Y.C; Yu, C.J.; Wang, H.C. 2007. Polypores from eastern Xizang (Tibet), western China. Ann. Bot. Fennici 44:135–145.
Sotome, K; Hattori, T.; Ota, Y. 2011. Taxonomic study on a threatened polypore, Polyporus pseudobetulinus, and a morphologically similar species, P. subvarius.