J Syst Evol ›› 1981, Vol. 19 ›› Issue (1): 29-42.

• Research Articles •

### Classification, distribution and phylogeny of the genus Ottelia

Li Hen

• Published:1981-02-18

Abstract: The genus Ottelia is one of the great genera of Hydrocharidaceae. About 25 species distributed in the Palaeotropics, extending from Africa through India and SE. Asia to Korea and Japan, Australia and New Caledonia, 1 species in Brazil; centres of specific devolopment are found in Central Africa and SE Asia. The present study is mainly based on the materials collected during the field explorations in the lakes of Yunnan and observations on the structure of the spathe and flowers, the variation of leaf of the plants cultivated in Kunming Bot. Garden. Instead of the wings of the spathe used by Dandy, by the characters such as uni-or bisexual flowers, this genus is divided into two subgenera, which by the number of the flowers in spathe and the number of the carpus in ovary again subdivided into 4 sections. They are as the following: A. Subg. Ottelia. Flowers bisexual. Sect. 1. Ottelia. Spathe with 1 flower; ovary with 6(—9) carpus. Sect. 2. Oligolobos (Gagnep.) Dandy. Spathe with many flowers; ovary with 3 carpus. B. Subg. Boottia (Wall.) Dandy. Flowers unisexual; the male spathe with 1-many flowers, the female spathe with many flowers. Sect. 3. Boottia. The male spathe with 1 flower; ovary with 9(—15) carpus. Sect. 4. Xystrolobos (Gagnep.) H. Li. The female spathe with (2-) many flowers; ovary with 3 or 9 carpus. The Chinense species of ottelia is in great need for revision. All of the species in China previousely described under Ottelia Pers, Boottia Wall., Oligolobos Gagnep, and Xystrolobos Gagen. are here combined into 3 species. They are O. alismoides, O. cordata, O. acuminata with 4 variaties. After a study of the geographic distribution and infer relation-ships among the floristic elements it has been proved that Ottelia is certainly an ancient genus, and the primitive types came into being and widely dispersed before the separation of Laurasia from Gondwana. During a considerable period of time the elements of the genus Ottelia in freshwater environment of different continents have been separately differentiated and evolved into more or less derived types. The structure of flowers in all of the asian species shows the following evolutionary tendenoes: 1. In this genus the plants with unisexual flowers have evolved from plants with bisexual flower; 2. In the groups with bisexual or unisexual flowers the number of stamens and styles reduced to 3-merous, but the number of flowers in spathe increased. So that the subgenus Ottelia is more primitive than the subgenus Bottia; While in the subgenus Ottelia O. alismoides is a more primitive than O. balansae and in the subgenus Boottia O. cordata is the most primitive, butO. alata seems to be the most advanced.