XVI International Botanical Congess

Euphorbia subg. Eremophyton is a disjunct group of ca. 20 species distributed in Africa and Australia. The Australian species consists of five annual or perennial species with succulent upper branches. Euphorbia planiticola is a cytologically unknown, and E. tannensis and E. parvicaruncula are diploid (2n=14), and E. boophthona and E. stevenii are polyploid (2n=42, 84, 56). The recent cytological evidence proposed that E. stevenii and E. boophthona should be evolved by the polyploidization, but the parentage of the species was not clarified. Phenetic and cladistic analyses using morphological characters, and isozyme electrophoresis from the five species of 28 natural populations throughout their range were conducted to clarify the parentage of E. stevenii and E. boophthona.