Polypore survey of Finland 5. The genus Polyporus

Distribution maps are presented for nine Polyporus species occurring in Finland. The commonest are P. brumalis (Pers.: Fr.) Fr. and P. ciliatus Fr.: Fr. A strictly southern species is P. badius (Pers.) Schw., which has been found in two places only, and to a lesser extent P. umbellatus (Pers.: Fr.) Fr.; both of these are classified as threatened. A widespread species with a southern emphasis is P. melanopus (Pers.: Fr.) Fr., from which P. tubaeformis Karst has been separated. P. pseudobetulinus (Pi!.) Thorn, Kotiranta & Niemelli (syn. Piptoporus p.) has two localities in Finland and is considered to be threatened. P. squamosus (Huds.: Fr.) Fr. is sparsely distributed over the whole country and has two ecotypes, one growing on large park trees in old towns in the south, and the other a dwarfed kind inhabiting riparian thickets and having a northerly distribution. P. leptocephalus (Jacq.: Fr.) Fr. (P. varius (Pers.: Fr.) Fr.) has a similar dual ecology, occurring both on dead, old-forest aspen trunks and on living park trees of various genera. All the species cause a white-rot, and, except for some questionable records from conifers, grow exclusively on hardwoods. Only P. squamosus does significant harm as a pathogen, causing decay in park trees.