XVI International Botanical Congess
Two allozymically distinct types, the north type and the south type, have been found in C. thalictroides (4X) in Japan. The north type tends to form fertile leaves promptly under short-day and/or low-temperature conditions. Breeding tests between these types and foreign sources indicate that C. thalictroides in the world may be assorted into two major groups associated with these types. Two groups are remarkably but still not completely intersterile. The following pattern of speciation is thus likely: Two ancestral tetraploids originated independently through hybridization between several interfertile diploid strains. One expanded into tropical and subtropical regions, while the other into temperate regions owing to its tendency to form fertile leaves promptly under the conditions mentioned above.