The role of the ‘Suthasinobon’ complex in introgressive hybridization

Abstract

Introgressive hybridization or introgression is the transfer of gene between two distinct species by the production of viable fertile hybrids. ‘Suthasinobon’ is an introduced day-blooming waterlily identified as Nymphaea capensis var. zanzibariensis. Together with its selections and hybrids, they are known as ‘Suthsinobon’ complex. Both ‘Suthasinobon’ and its complex are beautiful, aggressive plants and are popular among Thai waterlily growers. They hybridize readily with other Nymphaea species in the subgenus Brachyceras, including the only native day-blooming species, Nymphaea nouchali, known in Thai as ‘Bua Phan’ and ‘Bua Phuean’ which are two forms of N. nouchali, and ‘Bua Khap’ - N. nouchali var. cyanea. Evidences of introgression involving ‘Suthasinobon’ complex have been accumulated in the present study. The consequences of introgression are the breakdown of reproductive isolation, the loss of Thai native species of day-blooming waterlily, and the predominance of mongrels of partially hybrid ancestry closely resemble ‘Suthasinobon’ parent.