There are two pathogenic species of Typhula which cause snow mold in Japan, i.e. T. incarnata and T. ishikariensis. T. ishikariensis includes biotypes A and B, and isolates of biotype B show continuous variation associated with climatic conditions in winter. The distribution patterns of these fungi are allopatric. T. incarnate is ubiquitous with versatility in various ecological characteristics. Typhula ishikariensis biotype A distributes in snowy areas. Although its aggressiveness is intermediate, its strong competitive ability for less hardened plants enables the fungus to prevail in snowy areas, monopolizing the best resources for the pathogens. Biotype B exists mainly in less-snowy areas, where the host plants are rather hardy. However, strong aggressiveness of biotype B allows the fungus to attack those resources without waiting for the deterioration of the host plants under snow cover conditions. It is concluded that T. Incarnata has a general adaptability, while T. ishikariensis has a specific adaptability to varying environments.