 In North America , Suillus americanus has a similar appearance , but a more easterly distribution . It is associated with eastern white pine . Although some authors have tried to distinguish between the two with by using width of the stem , or by differences in fruit body colouration , it is acknowledged that these characteristics are variable , and depend on environmental factors . The phylogenetic analysis of Wu and colleagues ( 2000 ) suggests that the two taxa may be the same , although more samples from different geographical areas will be needed to verify this . 
