Origin of Triploids of Elatostema suzukii (Urticaceae) on Okinawa Island, the Ryukyus

Elatostema suzukii , an endemic species occurring only along streams in the Yanbaru area in the north of Okinawa Island, the Ryukyus, is known to comprise di-, tri-, and tetraploids with x=13. Molecular analysis of chloroplast DNA sequences has shown that two haplotypes, AT- and NI-types, characterized by the insertion or deletion of four nucleotides “ATAT”, exist in E. suzukii. The AT-type was found in some diploids and triploids only at Genkagawa, whereas the NI-type is widespread, occurring in both diploids and triploids of the Genkagawa site as well as at other localities. The triploids share both types with the diploids, indicating that the triploids have at least two independent origins. Because of its restricted distribution, the AT-type triploid may have arisen within the Genkagawa area. Received 16 October 2000/ Accepted in revised form 18 June 2001